remove HZ dependency from the granularity default. Use 10 msec for
the base granularity, 1 msec for wakeup granularity and 25 msec for
batch wakeup granularity. (These defaults are close to the values
that the default HZ=250 setting got previously, and thus it's the
most common setting.)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Michael Gerdau reported reniced task CPU usage weirdnesses.
Such symptoms can be caused by limit underruns so double the
sched_runtime_limit.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Was playing with sched_smt_power_savings/sched_mc_power_savings and
found out that while the scheduler domains are reconstructed when sysfs
settings change, rebalance_domains() can get triggered with null domain
on other cpus, which is setting next_balance to jiffies + 60*HZ.
Resulting in no idle/busy balancing for 60 seconds.
Fix this.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
On a four package system with HT - HT load balancing optimizations were
broken. For example, if two tasks end up running on two logical threads
of one of the packages, scheduler is not able to pull one of the tasks
to a completely idle package.
In this scenario, for nice-0 tasks, imbalance calculated by scheduler
will be 512 and find_busiest_queue() will return 0 (as each cpu's load
is 1024 > imbalance and has only one task running).
Similarly MC scheduler optimizations also get fixed with this patch.
[ mingo@elte.hu: restored fair balancing by increasing the fuzz and
adding it back to the power decision, without the /2
factor. ]
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
There are two remaining gotchas:
- The directories have impossible permissions (writeable).
- The ctl_name for the kernel directory is inconsistent with
everything else. It should be CTL_KERN.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
construct a more or less wall-clock time out of sched_clock(), by
using ACPI-idle's existing knowledge about how much time we spent
idling. This allows the rq clock to work around TSC-stops-in-C2,
TSC-gets-corrupted-in-C3 type of problems.
( Besides the scheduler's statistics this also benefits blktrace and
printk-timestamps as well. )
Furthermore, the precise before-C2/C3-sleep and after-C2/C3-wakeup
callbacks allow the scheduler to get out the most of the period where
the CPU has a reliable TSC. This results in slightly more precise
task statistics.
the ACPI bits were acked by Len.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Len Brown <len.brown@intel.com>
rebalance_domains(SCHED_IDLE) looks strange (typo), change it to CPU_IDLE.
the effect of this bug was slightly more agressive idle-balancing on
SMP than intended.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch makes the following needlessly global code static:
- arch_reinit_sched_domains()
- struct attr_sched_mc_power_savings
- struct attr_sched_smt_power_savings
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
improve the rq-clock overflow logic: limit the absolute rq->clock
delta since the last scheduler tick, instead of limiting the delta
itself.
tested by Arjan van de Ven - whole laptop was misbehaving due to
an incorrectly calibrated cpu_khz confusing sched_clock().
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
round a tiny bit better in high-frequency rescheduling scenarios,
by rounding around zero instead of rounding down.
(this is pretty theoretical though)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
optimize update_rq_clock() calls in the load-balancer: update them
right after locking the runqueue(s) so that the pull functions do
not have to call it.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
optimize activate_task() by removing update_rq_clock() from it.
(and add update_rq_clock() to all callsites of activate_task() that
did not have it before.)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
move the __update_rq_clock() call from update_cpu_load() to
scheduler_tick().
( identity transformation that causes no change in functionality. )
this allows the direct use of rq->clock in ->task_tick() functions.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
final step: remove all (now superfluous) 'u64 now' variables.
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from deactivate_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from dequeue_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from enqueue_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from dec_nr_running().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from inc_nr_running().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from dec_load().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from inc_load().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from update_curr_load().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from ->task_new().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from ->put_prev_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from pick_next_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from ->pick_next_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from ->dequeue_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from ->enqueue_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
change all 'now' timestamp uses in assignments to rq->clock.
( this is an identity transformation that causes no functionality change:
all such new rq->clock is necessarily preceded by an update_rq_clock()
call. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
eliminate __rq_clock() use by changing it to:
__update_rq_clock(rq)
now = rq->clock;
identity transformation - no change in behavior.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
eliminate rq_clock() use by changing it to:
update_rq_clock(rq)
now = rq->clock;
identity transformation - no change in behavior.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
add the [__]update_rq_clock(rq) functions. (No change in functionality,
just reorganization to prepare for elimination of the heavy 64-bit
timestamp-passing in the scheduler.)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
There are two problems with balance_tasks() and how it used:
1. The variables best_prio and best_prio_seen (inherited from the old
move_tasks()) were only required to handle problems caused by the
active/expired arrays, the order in which they were processed and the
possibility that the task with the highest priority could be on either.
These issues are no longer present and the extra overhead associated
with their use is unnecessary (and possibly wrong).
2. In the absence of CONFIG_FAIR_GROUP_SCHED being set, the same
this_best_prio variable needs to be used by all scheduling classes or
there is a risk of moving too much load. E.g. if the highest priority
task on this at the beginning is a fairly low priority task and the rt
class migrates a task (during its turn) then that moved task becomes the
new highest priority task on this_rq but when the sched_fair class
initializes its copy of this_best_prio it will get the priority of the
original highest priority task as, due to the run queue locks being
held, the reschedule triggered by pull_task() will not have taken place.
This could result in inappropriate overriding of skip_for_load and
excessive load being moved.
The attached patch addresses these problems by deleting all reference to
best_prio and best_prio_seen and making this_best_prio a reference
parameter to the various functions involved.
load_balance_fair() has also been modified so that this_best_prio is
only reset (in the loop) if CONFIG_FAIR_GROUP_SCHED is set. This should
preserve the effect of helping spread groups' higher priority tasks
around the available CPUs while improving system performance when
CONFIG_FAIR_GROUP_SCHED isn't set.
Signed-off-by: Peter Williams <pwil3058@bigpond.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
kernel.sched_domain hierarchy is under CTL_UNNUMBERED and thus
unreachable to sysctl(2). Generating .ctl_number's in such situation is
not useful.
Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
speed up schedule(): share the 'now' parameter that deactivate_task()
was calculating internally.
( this also fixes the small accounting window between the deactivate
call and the pick_next_task() call. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
uninline rq_clock() to save 263 bytes of code:
text data bss dec hex filename
39561 3642 24 43227 a8db sched.o.before
39298 3642 24 42964 a7d4 sched.o.after
Signed-off-by: Ingo Molnar <mingo@elte.hu>
here's another tiny cleanup. The generated code is not affected (gcc is
smart enough) but for people looking over the code it is just irritating
to have the extra conditional.
Signed-off-by: Ulrich Drepper <drepper@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The move_tasks() function is currently multiplexed with two distinct
capabilities:
1. attempt to move a specified amount of weighted load from one run
queue to another; and
2. attempt to move a specified number of tasks from one run queue to
another.
The first of these capabilities is used in two places, load_balance()
and load_balance_idle(), and in both of these cases the return value of
move_tasks() is used purely to decide if tasks/load were moved and no
notice of the actual number of tasks moved is taken.
The second capability is used in exactly one place,
active_load_balance(), to attempt to move exactly one task and, as
before, the return value is only used as an indicator of success or failure.
This multiplexing of sched_task() was introduced, by me, as part of the
smpnice patches and was motivated by the fact that the alternative, one
function to move specified load and one to move a single task, would
have led to two functions of roughly the same complexity as the old
move_tasks() (or the new balance_tasks()). However, the new modular
design of the new CFS scheduler allows a simpler solution to be adopted
and this patch addresses that solution by:
1. adding a new function, move_one_task(), to be used by
active_load_balance(); and
2. making move_tasks() a single purpose function that tries to move a
specified weighted load and returns 1 for success and 0 for failure.
One of the consequences of these changes is that neither move_one_task()
or the new move_tasks() care how many tasks sched_class.load_balance()
moves and this enables its interface to be simplified by returning the
amount of load moved as its result and removing the load_moved pointer
from the argument list. This helps simplify the new move_tasks() and
slightly reduces the amount of work done in each of
sched_class.load_balance()'s implementations.
Further simplification, e.g. changes to balance_tasks(), are possible
but (slightly) complicated by the special needs of load_balance_fair()
so I've left them to a later patch (if this one gets accepted).
NB Since move_tasks() gets called with two run queue locks held even
small reductions in overhead are worthwhile.
[ mingo@elte.hu ]
this change also reduces code size nicely:
text data bss dec hex filename
39216 3618 24 42858 a76a sched.o.before
39173 3618 24 42815 a73f sched.o.after
Signed-off-by: Peter Williams <pwil3058@bigpond.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Peter Williams suggested to flip the order of update_cpu_load(rq) with
the ->task_tick() call. This is a NOP for the current scheduler (the
two functions are independent of each other), ->task_tick() might
create some state for update_cpu_load() in the future (or in PlugSched).
Signed-off-by: Ingo Molnar <mingo@elte.hu>
move the rest of the debugging/instrumentation code to under
CONFIG_SCHEDSTATS too. This reduces code size and speeds code up:
text data bss dec hex filename
33044 4122 28 37194 914a sched.o.before
32708 4122 28 36858 8ffa sched.o.after
Signed-off-by: Ingo Molnar <mingo@elte.hu>
1. The only place that RTPRIO_TO_LOAD_WEIGHT() is used is in the call to
move_tasks() in the function active_load_balance() and its purpose here
is just to make sure that the load to be moved is big enough to ensure
that exactly one task is moved (if there's one available). This can be
accomplished by using ULONG_MAX instead and this allows
RTPRIO_TO_LOAD_WEIGHT() to be deleted.
2. This, in turn, allows PRIO_TO_LOAD_WEIGHT() to be deleted.
3. This allows load_weight() to be deleted which allows
TIME_SLICE_NICE_ZERO to be deleted along with the comment above it.
Signed-off-by: Peter Williams <pwil3058@bigpond.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Fix kernel-doc warnings in sched.c:
Warning(linux-2623-rc1g4//kernel/sched.c:1685): No description found for parameter 'notifier'
Warning(linux-2623-rc1g4//kernel/sched.c:1696): No description found for parameter 'notifier'
Warning(linux-2623-rc1g4//kernel/sched.c:1750): No description found for parameter 'prev'
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
debugging feature: make the sched-domains tree runtime-tweakable.
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
[ mingo@elte.hu: made it depend on CONFIG_SCHED_DEBUG & small updates ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
it is enough to disable interrupts to get the precise rq-clock
of the local CPU.
this also solves an NMI watchdog regression: the NMI watchdog
calls touch_softlockup_watchdog(), which might deadlock on
rq->lock if the NMI hits an rq-locked critical section.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This adds a general mechanism whereby a task can request the scheduler to
notify it whenever it is preempted or scheduled back in. This allows the
task to swap any special-purpose registers like the fpu or Intel's VT
registers.
Signed-off-by: Avi Kivity <avi@qumranet.com>
[ mingo@elte.hu: fixes, cleanups ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Implement the cpu_clock(cpu) interface for kernel-internal use:
high-speed (but slightly incorrect) per-cpu clock constructed from
sched_clock().
This API, unused at the moment, will be used in the future by blktrace,
by the softlockup-watchdog, by printk and by lockstat.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
nr_moved is not the correct check for triggering all pinned logic. Fix
the all pinned logic in the case of load_balance_newidle().
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In the presence of SMT, newly idle balance was never happening for
multi-core and SMP domains (even when both the logical siblings are
idle).
If thread 0 is already idle and when thread 1 is about to go to idle,
newly idle load balance always think that one of the threads is not idle
and skips doing the newly idle load balance for multi-core and SMP
domains.
This is because of the idle_cpu() macro, which checks if the current
process on a cpu is an idle process. But this is not the case for the
thread doing the load_balance_newidle().
Fix this by using runqueue's nr_running field instead of idle_cpu(). And
also skip the logic of 'only one idle cpu in the group will be doing
load balancing' during newly idle case.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Currently most of the per cpu data, which is accessed by different cpus,
has a ____cacheline_aligned_in_smp attribute. Move all this data to the
new per cpu shared data section: .data.percpu.shared_aligned.
This will seperate the percpu data which is referenced frequently by other
cpus from the local only percpu data.
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently, the freezer treats all tasks as freezable, except for the kernel
threads that explicitly set the PF_NOFREEZE flag for themselves. This
approach is problematic, since it requires every kernel thread to either
set PF_NOFREEZE explicitly, or call try_to_freeze(), even if it doesn't
care for the freezing of tasks at all.
It seems better to only require the kernel threads that want to or need to
be frozen to use some freezer-related code and to remove any
freezer-related code from the other (nonfreezable) kernel threads, which is
done in this patch.
The patch causes all kernel threads to be nonfreezable by default (ie. to
have PF_NOFREEZE set by default) and introduces the set_freezable()
function that should be called by the freezable kernel threads in order to
unset PF_NOFREEZE. It also makes all of the currently freezable kernel
threads call set_freezable(), so it shouldn't cause any (intentional)
change of behaviour to appear. Additionally, it updates documentation to
describe the freezing of tasks more accurately.
[akpm@linux-foundation.org: build fixes]
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Nigel Cunningham <nigel@nigel.suspend2.net>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
improve the comments around the wmult array (which controls the weight
of niced tasks). Clarify that to achieve a 10% difference in CPU
utilization, a weight multiplier of 1.25 has to be used.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Roman Zippel noticed another inconsistency of the wmult table.
wmult[16] has a missing digit.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fix show_task()/show_tasks() output:
- there's no sibling info anymore
- the fields were not aligned properly with the description
- get rid of the lazy-TLB output: it's been quite some time since
we last had a bug there, and when we had a bug it wasnt helped a
bit by this debug output.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There's a typo in the values in prio_to_wmult[] for nice level 1. While
it did not cause bad CPU distribution, but caused more rescheduling
between nice-0 and nice-1 tasks than necessary.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
add credits for recent major scheduler contributions:
Con Kolivas, for pioneering the fair-scheduling approach
Peter Williams, for smpnice
Mike Galbraith, for interactivity tuning of CFS
Srivatsa Vaddagiri, for group scheduling enhancements
Signed-off-by: Ingo Molnar <mingo@elte.hu>
clean up the sleep_on() APIs:
- do not use fastcall
- replace fragile macro magic with proper inline functions
Signed-off-by: Ingo Molnar <mingo@elte.hu>
4 small style cleanups to sched.c: checkpatch.pl is now happy about
the totality of sched.c [ignoring false positives] - yay! ;-)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
track TSC-unstable events and propagate it to the scheduler code.
Also allow sched_clock() to be used when the TSC is unstable,
the rq_clock() wrapper creates a reliable clock out of it.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
apply the CFS core code.
this change switches over the scheduler core to CFS's modular
design and makes use of kernel/sched_fair/rt/idletask.c to implement
Linux's scheduling policies.
thanks to Andrew Morton and Thomas Gleixner for lots of detailed review
feedback and for fixlets.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
remove the sleep-bonus interactivity code from the core scheduler.
scheduling policy is implemented in the policy modules, and CFS does
not need such type of heuristics.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the expired_starving() heuristics from the core scheduler.
CFS does not need it, and this did not really work well in practice
anyway, due to the rq->nr_running multiplier to STARVATION_LIMIT.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the sleep_type heuristics from the core scheduler - scheduling
policy is implemented in the scheduling-policy modules. (and CFS does
not use this type of sleep-type heuristics)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
cleanup: move dequeue/enqueue_task() to a more logical place, to
not split up __normal_prio()/normal_prio().
Signed-off-by: Ingo Molnar <mingo@elte.hu>
move resched_task()/resched_cpu() into the 'public interfaces'
section of sched.c, for use by kernel/sched_fair/rt/idletask.c
Signed-off-by: Ingo Molnar <mingo@elte.hu>
add rq_clock()/__rq_clock(), a robust wrapper around sched_clock(),
used by CFS. It protects against common type of sched_clock() problems
(caused by hardware): time warps forwards and backwards.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
add the CFS rq data types to sched.c.
(the old scheduler fields are still intact, they are removed
by a later patch)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
create sched_stats.h and move sched.c schedstats code into it.
This cleans up sched.c a bit.
no code changes are caused by this patch.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
add the init_idle_bootup_task() callback to the bootup thread,
unused at the moment. (CFS will use it to switch the scheduling
class of the boot thread to the idle class)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove sched_exit(): the elaborate dance of us trying to recover
timeslices given to child tasks never really worked.
CFS does not need it either.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
the SMP load-balancer uses the boot-time migration-cost estimation
code to attempt to improve the quality of balancing. The reason for
this code is that the discrete priority queues do not preserve
the order of scheduling accurately, so the load-balancer skips
tasks that were running on a CPU 'recently'.
this code is fundamental fragile: the boot-time migration cost detector
doesnt really work on systems that had large L3 caches, it caused boot
delays on large systems and the whole cache-hot concept made the
balancing code pretty undeterministic as well.
(and hey, i wrote most of it, so i can say it out loud that it sucks ;-)
under CFS the same purpose of cache affinity can be achieved without
any special cache-hot special-case: tasks are sorted in the 'timeline'
tree and the SMP balancer picks tasks from the left side of the
tree, thus the most cache-cold task is balanced automatically.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
enum idle_type (used by the load-balancer) clashes with the
SCHED_IDLE name that we want to introduce. 'CPU_IDLE' instead
of 'SCHED_IDLE' is more descriptive as well.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The intervals of domains that do not have SD_BALANCE_NEWIDLE must be
considered for the calculation of the time of the next balance. Otherwise
we may defer rebalancing forever.
Siddha also spotted that the conversion of the balance interval
to jiffies is missing. Fix that to.
From: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
also continue the loop if !(sd->flags & SD_LOAD_BALANCE).
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
It did in fact trigger under all three of mainline, CFS, and -rt including CFS
-- see below for a couple of emails from last Friday giving results for these
three on the AMD box (where it happened) and on a single-quad NUMA-Q system
(where it did not, at least not with such severity).
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Miklos Szeredi reported very long pauses (several seconds, sometimes
more) on his T60 (with a Core2Duo) which he managed to track down to
wait_task_inactive()'s open-coded busy-loop.
He observed that an interrupt on one core tries to acquire the
runqueue-lock but does not succeed in doing so for a very long time -
while wait_task_inactive() on the other core loops waiting for the first
core to deschedule a task (which it wont do while spinning in an
interrupt handler).
This rewrites wait_task_inactive() to do all its waiting optimistically
without any locks taken at all, and then just double-check the end
result with the proper runqueue lock held over just a very short
section. If there were races in the optimistic wait, of a preemption
event scheduled the process away, we simply re-synchronize, and start
over.
So the code now looks like this:
repeat:
/* Unlocked, optimistic looping! */
rq = task_rq(p);
while (task_running(rq, p))
cpu_relax();
/* Get the *real* values */
rq = task_rq_lock(p, &flags);
running = task_running(rq, p);
array = p->array;
task_rq_unlock(rq, &flags);
/* Check them.. */
if (unlikely(running)) {
cpu_relax();
goto repeat;
}
/* Preempted away? Yield if so.. */
if (unlikely(array)) {
yield();
goto repeat;
}
Basically, that first "while()" loop is done entirely without any
locking at all (and doesn't check for the case where the target process
might have been preempted away), and so it's possibly "incorrect", but
we don't really care. Both the runqueue used, and the "task_running()"
check might be the wrong tests, but they won't oops - they just mean
that we could possibly get the wrong results due to lack of locking and
exit the loop early in the case of a race condition.
So once we've exited the loop, we then get the proper (and careful) rq
lock, and check the running/runnable state _safely_. And if it turns
out that our quick-and-dirty and unsafe loop was wrong after all, we
just go back and try it all again.
(The patch also adds a lot of comments, which is the actual bulk of it
all, to make it more obvious why we can do these things without holding
the locks).
Thanks to Miklos for all the testing and tracking it down.
Tested-by: Miklos Szeredi <miklos@szeredi.hu>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Gene Heskett reported the following problem while testing CFS: SysRq-N
is not always effective in normalizing tasks back to SCHED_OTHER.
The reason for that turns out to be the following bug:
- normalize_rt_tasks() uses for_each_process() to iterate through all
tasks in the system. The problem is, this method does not iterate
through all tasks, it iterates through all thread groups.
The proper mechanism to enumerate over all threads is to use a
do_each_thread() + while_each_thread() loop.
Reported-by: Gene Heskett <gene.heskett@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The NOHZ patch contains a check for softirqs pending when a CPU goes idle.
The BUG is unrelated to NOHZ, it just was made visible by the NOHZ patch.
The BUG showed up mainly on P4 / hyperthreading enabled machines which lead
the investigations into the wrong direction in the first place. The real
cause is in cond_resched_softirq():
cond_resched_softirq() is enabling softirqs without invoking the softirq
daemon when softirqs are pending. This leads to the warning message in the
NOHZ idle code:
t1 runs softirq disabled code on CPU#0
interrupt happens, softirq is raised, but deferred (softirqs disabled)
t1 calls cond_resched_softirq()
enables softirqs via _local_bh_enable()
calls schedule()
t2 runs
t1 is migrated to CPU#1
t2 is done and invokes idle()
NOHZ detects the pending softirq
Fix: change _local_bh_enable() to local_bh_enable() so the softirq
daemon is invoked.
Thanks to Anant Nitya for debugging this with great patience !
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since nonboot CPUs are now disabled after tasks and devices have been
frozen and the CPU hotplug infrastructure is used for this purpose, we need
special CPU hotplug notifications that will help the CPU-hotplug-aware
subsystems distinguish normal CPU hotplug events from CPU hotplug events
related to a system-wide suspend or resume operation in progress. This
patch introduces such notifications and causes them to be used during
suspend and resume transitions. It also changes all of the
CPU-hotplug-aware subsystems to take these notifications into consideration
(for now they are handled in the same way as the corresponding "normal"
ones).
[oleg@tv-sign.ru: cleanups]
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Eliminate lock_cpu_hotplug from kernel/sched.c and use sched_hotcpu_mutex
instead to postpone a hotplug event.
In the migration_call hotcpu callback function, take sched_hotcpu_mutex
while handling the event CPU_LOCK_ACQUIRE and release it while handling
CPU_LOCK_RELEASE event.
[akpm@linux-foundation.org: fix deadlock]
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Revert commit bd53f96ca5.
Con says:
This is no good, sorry. The one I saw originally was with the staircase
deadline cpu scheduler in situ and was different.
#define TASK_PREEMPTS_CURR(p, rq) \
((p)->prio < (rq)->curr->prio)
(((p)->prio < (rq)->curr->prio) && ((p)->array == (rq)->active))
This will fail to wake up a runqueue for a task that has been migrated to the
expired array of a runqueue which is otherwise idle which can happen with smp
balancing,
Cc: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Cc: Con Kolivas <kernel@kolivas.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Align the per cpu runqueue to the cacheline boundary. This will minimize
the number of cachelines touched during remote wakeup.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Ravikiran G Thirumalai <kiran@scalex86.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- Make TASK_PREEMPTS_CURR(task, rq) return "true" only if the task's prio
is higher than the current's one and the task is in the "active" array.
This ensures we don't make redundant resched_task() calls when the task
is in the "expired" array (as may happen now in set_user_prio(),
rt_mutex_setprio() and pull_task() ) ;
- generalise conditions for a call to resched_task() in set_user_nice(),
rt_mutex_setprio() and sched_setscheduler()
Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Cc: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When a logical cpu 'x' already has more than one process running, then most
likely the siblings of that cpu 'x' must be busy. Otherwise the idle
siblings would have likely(in most of the scenarios) picked up the extra
load making the load on 'x' atmost one.
Use this logic to eliminate the siblings status check and minimize the cache
misses encountered on a heavily loaded system.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I noticed expensive divides done in try_to_wakeup() and
find_busiest_group() on a bi dual core Opteron machine (total of 4 cores),
moderatly loaded (15.000 context switch per second)
oprofile numbers :
CPU: AMD64 processors, speed 2600.05 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Cycles outside of halt state) with a unit
mask of 0x00 (No unit mask) count 50000
samples % symbol name
...
613914 1.0498 try_to_wake_up
834 0.0013 :ffffffff80227ae1: div %rcx
77513 0.1191 :ffffffff80227ae4: mov %rax,%r11
608893 1.0413 find_busiest_group
1841 0.0031 :ffffffff802260bf: div %rdi
140109 0.2394 :ffffffff802260c2: test %sil,%sil
Some of these divides can use the reciprocal divides we introduced some
time ago (currently used in slab AFAIK)
We can assume a load will fit in a 32bits number, because with a
SCHED_LOAD_SCALE=128 value, its still a theorical limit of 33554432
When/if we reach this limit one day, probably cpus will have a fast
hardware divide and we can zap the reciprocal divide trick.
Ingo suggested to rename cpu_power to __cpu_power to make clear it should
not be modified without changing its reciprocal value too.
I did not convert the divide in cpu_avg_load_per_task(), because tracking
nr_running changes may be not worth it ? We could use a static table of 32
reciprocal values but it would add a conditional branch and table lookup.
[akpm@linux-foundation.org: !SMP build fix]
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix the process idle load balancing in the presence of dynticks. cpus for
which ticks are stopped will sleep till the next event wakes it up.
Potentially these sleeps can be for large durations and during which today,
there is no periodic idle load balancing being done.
This patch nominates an owner among the idle cpus, which does the idle load
balancing on behalf of the other idle cpus. And once all the cpus are
completely idle, then we can stop this idle load balancing too. Checks added
in fast path are minimized. Whenever there are busy cpus in the system, there
will be an owner(idle cpu) doing the system wide idle load balancing.
Open items:
1. Intelligent owner selection (like an idle core in a busy package).
2. Merge with rcu's nohz_cpu_mask?
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Periodic load balancing in recent kernels happen in the softirq. In
certain -rt configurations, these softirqs are handled in softirqd context.
And hence the check for idle processor was always returning busy (as
nr_running > 1).
This patch captures the idle information at the tick and passes this info
to softirq context through an element 'idle_at_tick' in rq.
[kernel@kolivas.org: Fix reverse idle at tick logic]
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add touch_all_softlockup_watchdogs() to allow the softlockup watchdog
timers on all cpus to be updated. This is used to prevent sysrq-t from
generating a spurious watchdog message when generating lots of output.
Softlockup watchdogs use sched_clock() as its timebase, which is inherently
per-cpu (at least, when it is measuring unstolen time). Because of this,
it isn't possible for one CPU to directly update the other CPU's timers,
but it is possible to tell the other CPUs to do update themselves
appropriately.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Acked-by: Chris Lalancette <clalance@redhat.com>
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: Rick Lindsley <ricklind@us.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The nr_cpu_ids value is currently only calculated in smp_init. However, it
may be needed before (SLUB needs it on kmem_cache_init!) and other kernel
components may also want to allocate dynamically sized per cpu array before
smp_init. So move the determination of possible cpus into sched_init()
where we already loop over all possible cpus early in boot.
Also initialize both nr_node_ids and nr_cpu_ids with the highest value they
could take. If we have accidental users before these values are determined
then the current valud of 0 may cause too small per cpu and per node arrays
to be allocated. If it is set to the maximum possible then we only waste
some memory for early boot users.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
show_state() (SysRq-T) developed the buggy habbit of not showing
TASK_RUNNING tasks. This was due to the mistaken belief that state_filter
== -1 would be a pass-through filter - while in reality it did not let
TASK_RUNNING == 0 p->state values through.
Fix this by restoring the original '!state_filter means all tasks'
special-case i had in the original version. Test-built and test-booted on
i686, SysRq-T now works as intended.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
the p->parent PID printout gives us all the information about the
task tree that we need - the eldest_child()/older_sibling()/
younger_sibling() printouts are mostly historic and i do not
remember ever having used those fields. (IMO in fact they confuse
the SysRq-T output.) So remove them.
This code has sentimental value though, those fields and
printouts are one of the oldest ones still surviving from
Linux v0.95's kernel/sched.c:
if (p->p_ysptr || p->p_osptr)
printk(" Younger sib=%d, older sib=%d\n\r",
p->p_ysptr ? p->p_ysptr->pid : -1,
p->p_osptr ? p->p_osptr->pid : -1);
else
printk("\n\r");
written 15 years ago, in early 1992.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus 'snif' Torvalds <torvalds@linux-foundation.org>
Remove the SMT-nice feature which idles sibling cpus on SMT cpus to
facilitiate nice working properly where cpu power is shared. The idling of
cpus in the presence of runnable tasks is considered too fragile, easy to
break with outside code, and the complexity of managing this system if an
architecture comes along with many logical cores sharing cpu power will be
unworkable.
Remove the associated per_cpu_gain variable in sched_domains used only by
this code.
Also:
The reason is that with dynticks enabled, this code breaks without yet
further tweaks so dynticks brought on the rapid demise of this code. So
either we tweak this code or kill it off entirely. It was Ingo's preference
to kill it off. Either way this needs to happen for 2.6.21 since dynticks
has gone in.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The SMT scheduler incorrectly skips kernel threads even if they are
runnable (but they are preempted by a higher-prio user-space task which got
SMT-delayed by an even higher-priority task running on a sibling CPU).
Fix this for now by only doing the SMT-nice optimization if the
to-be-delayed task is the only runnable task. (This should cover most of
the real-life cases anyway.)
This bug has been in the SMT scheduler since 2.6.17 or so, but has only
been noticed now by the active check in the dynticks code.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Michal Piotrowski <michal.k.k.piotrowski@gmail.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Problem description at:
http://bugzilla.kernel.org/show_bug.cgi?id=8048
Commit b18ec80396
[PATCH] sched: improve migration accuracy
optimized the scheduler time calculations, but broke posix-cpu-timers.
The problem is that the p->last_ran value is not updated after a context
switch. So a subsequent call to current_sched_time() calculates with a
stale p->last_ran value, i.e. accounts the full time, which the task was
scheduled away.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The VMI ROM has a mode where hypercalls can be queued and batched. This turns
out to be a significant win during context switch, but must be done at a
specific point before side effects to CPU state are visible to subsequent
instructions. This is similar to the MMU batching hooks already provided.
The same hooks could be used by the Xen backend to implement a context switch
multicall.
To explain a bit more about lazy modes in the paravirt patches, basically, the
idea is that only one of lazy CPU or MMU mode can be active at any given time.
Lazy MMU mode is similar to this lazy CPU mode, and allows for batching of
multiple PTE updates (say, inside a remap loop), but to avoid keeping some
kind of state machine about when to flush cpu or mmu updates, we just allow
one or the other to be active. Although there is no real reason a more
comprehensive scheme could not be implemented, there is also no demonstrated
need for this extra complexity.
Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Avoid expensive integer divide 3 times per CPU per tick.
A userspace test of this loop went from 26ns, down to 19ns on a G5; and
from 123ns down to 28ns on a P3.
(Also avoid a variable bit shift, as suggested by Alan. The effect
of this wasn't noticable on the CPUs I tested with).
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A variety of (mostly) innocuous fixes to the embedded kernel-doc content in
source files, including:
* make multi-line initial descriptions single line
* denote some function names, constants and structs as such
* change erroneous opening '/*' to '/**' in a few places
* reword some text for clarity
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 5c1e176781 ("sched: force /sbin/init
off isolated cpus") sets init's cpus_allowed to a subset of cpu_online_map
at boot time, which means that tasks won't be scheduled on cpus that are
added to the system later.
Make init's cpus_allowed a subset of cpu_possible_map instead. This should
still preserve the behavior that Nick's change intended.
Thanks to Giuliano Pochini for reporting this and testing the fix:
http://ozlabs.org/pipermail/linuxppc-dev/2006-December/029397.html
Signed-off-by: Nathan Lynch <ntl@pobox.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove the __resched_legal() check: it is conceptually broken. The biggest
problem it had is that it can mask buggy cond_resched() calls. A
cond_resched() call is only legal if we are not in an atomic context, with
two narrow exceptions:
- if the system is booting
- a reacquire_kernel_lock() down() done while PREEMPT_ACTIVE is set
But __resched_legal() hid this and just silently returned whenever
these primitives were called from invalid contexts. (Same goes for
cond_resched_locked() and cond_resched_softirq()).
Furthermore, the __legal_resched(0) call was buggy in that it caused
unnecessarily long softirq latencies via cond_resched_softirq(). (which is
only called from softirq-off sections, hence the code did nothing.)
The fix is to resurrect the efficiency of the might_sleep checks and to
only allow the narrow exceptions.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The structure cpu_isolated_map is used not only during initialization.
Multi-core scheduler configuration changes and exclusive cpusets
use this during run time. During setting of sched_mc_power_savings
policy, this structure is accessed to update sched_domains.
Signed-off-by: Tim Chen <tim.c.chen@intel.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Commit 2d7d253548 ("fix cond_resched() fix")
introduced an 'expected_preempt_count' parameter to __resched_legal() to
fix a bug where it was returning a false negative when called from
cond_resched_lock() and preemption was enabled.
Unfortunately this broke things for when preemption is disabled.
preempt_count() will always return zero, thus failing the check against any
value of expected_preempt_count not equal to zero. cond_resched_lock() for
example, passes an expected_preempt_count value of 1.
So fix the fix for the cond_resched() fix by skipping the check of
preempt_count() against expected_preempt_count when preemption is disabled.
Credit should go to Sunil Mushran for spotting the bug during testing.
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Problem:
sched_fork() has always called scheduler_tick() in some (unlikely)
circumstances in order to update the current task in light of those
circumstances. It has always been the case that the work done by
scheduler_tick() was more than was required to handle the problem in
hand but no harm was done except for the waste of a few CPU cycles.
However, the splitting of scheduler_tick() into two procedures in
2.6.20-rc1 enables the wasted cycles to be saved as the new procedure
task_running_tick() does all the work that is required to rectify the
problem being handled.
Solution:
Replace the call to scheduler_tick() in sched_fork() with a call to
task_running_tick().
Signed-off-by: Peter Williams <pwil3058@bigpond.com.au>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
When we print an assert due to scheduling-in-atomic bugs, and if lockdep
is enabled, then the IRQ tracing information of lockdep can be printed
to pinpoint the code location that disabled interrupts. This saved me
quite a bit of debugging time in cases where the backtrace did not
identify the irq-disabling site well enough.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
RT task does not participate in interactiveness priority and thus shouldn't
be bothered with timestamp and p->sleep_type manipulation when task is
being put on run queue. Bypass all of the them with a single if (rt_task)
test.
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove scheduler stats lb_stopbalance counter. This counter can be
calculated by: lb_balanced - lb_nobusyg - lb_nobusyq. There is no need to
create gazillion counters while we can derive the value.
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Currently at a particular domain, each cpu in the sched group will do a
load balance at the frequency of balance_interval. More the cores and
threads, more the cpus will be in each sched group at SMP and NUMA domain.
And we endup spending quite a bit of time doing load balancing in those
domains.
Fix this by making only one cpu(first idle cpu or first cpu in the group if
all the cpus are busy) in the sched group do the load balance at that
particular sched domain and this load will slowly percolate down to the
other cpus with in that group(when they do load balancing at lower
domains).
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Co-opt rq->timestamp_last_tick to maintain a cache_hot_time evaluation
reference timestamp at both tick and sched times to prevent said reference,
formerly rq->timestamp_last_tick, from being behind task->last_ran at
evaluation time, and to move said reference closer to current time on the
remote processor, intent being to improve cache hot evaluation and
timestamp adjustment accuracy for task migration.
Fix minor sched_time double accounting error which occurs when a task
passing through schedule() does not schedule off, and takes the next timer
tick.
[kenneth.w.chen@intel.com: cleanup]
Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Ken Chen <kenneth.w.chen@intel.com>
Cc: Don Mullis <dwm@meer.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Large sched domains can be very expensive to scan. Add an option SD_SERIALIZE
to the sched domain flags. If that flag is set then we make sure that no
other such domain is being balanced.
[akpm@osdl.org: build fix]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Trigger softirq less frequently
We trigger the softirq before this patch using offset of sd->interval.
However, if the queue is busy then it is sufficient to schedule the softirq
with sd->interval * busy_factor.
So we modify the calculation of the next time to balance by taking
the interval added to last_balance again. This is only the
right value if the idle/busy situation continues as is.
There are two potential trouble spots:
- If the queue was idle and now gets busy then we call rebalance
early. However, that is not a problem because we will then use
the longer interval for the next period.
- If the queue was busy and becomes idle then we potentially
wait too long before rebalancing. However, when the task
goes idle then idle_balance is called. We add another calculation
of the next balance time based on sd->interval in idle_balance
so that we will rebalance soon.
V2->V3:
- Calculate rebalance time based on current jiffies and not
based on the jiffies at the last time we load balanced.
We no longer rely on staggering and therefore we can
affort to do this now.
V3->V4:
- Use functions to do jiffy comparisons.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Call rebalance_tick (renamed to run_rebalance_domains) from a newly introduced
softirq.
We calculate the earliest time for each layer of sched domains to be rescanned
(this is the rescan time for idle) and use the earliest of those to schedule
the softirq via a new field "next_balance" added to struct rq.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Perform the idle state determination in rebalance_tick.
If we separate balancing from sched_tick then we also need to determine the
idle state in rebalance_tick.
V2->V3
Remove useless idlle != 0 check. Checking nr_running seems
to be sufficient. Thanks Suresh.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
A load calculation is always done in rebalance_tick() in addition to the real
load balancing activities that only take place when certain jiffie counts have
been reached. Move that processing into a separate function and call it
directly from scheduler_tick().
Also extract the time slice handling from scheduler_tick and put it into a
separate function. Then we can clean up scheduler_tick significantly. It
will no longer have any gotos.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Interrupts must be disabled for request queue locks if we want to run
load_balance() with interrupts enabled.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Timer interrupts already are staggered. We do not need an additional layer of
time staggering for short load balancing actions that take a reasonably small
portion of the time slice.
For load balancing on large sched_domains we will add a serialization later
that avoids concurrent load balance operations and thus has the same effect as
load staggering.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Avoid taking the request queue lock in wake_priority_sleeper if there are no
running processes.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
move_task_off_dead_cpu() requires interrupts to be disabled, while
migrate_dead() calls it with enabled interrupts. Added appropriate
comments to functions and added BUG_ON(!irqs_disabled()) into
double_rq_lock() and double_lock_balance() which are the origin sources of
such bugs.
Signed-off-by: Kirill Korotaev <dev@openvz.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Move the sched group allocations to percpu area. This will minimize cross
node memory references and also cleans up the sched groups allocation for
allnodes sched domain.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
- move some file_operations structs into the .rodata section
- move static strings from policy_types[] array into the .rodata section
- fix generic seq_operations usages, so that those structs may be defined
as "const" as well
[akpm@osdl.org: couple of fixes]
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
At present show_state prints a header the does not match the output of
show_task, as follows:
-
sibling
task PC pid father child younger older
init S 00000000 0 1 0 2 (NOTLB)
-
This patch corrects the output of show_state so that the header is
aligned with the data, ala:
-
free sibling
task PC stack pid father child younger older
init S 00000000 0 1 0 2 (NOTLB)
-
Signed-off-by: Chris Caputo <ccaputo@alt.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
There was lots of #ifdef noise in the kernel due to hotcpu_notifier(fn,
prio) not correctly marking 'fn' as used in the !HOTPLUG_CPU case, and thus
generating compiler warnings of unused symbols, hence forcing people to add
#ifdefs.
the compiler can skip truly unused functions just fine:
text data bss dec hex filename
1624412 728710 3674856 6027978 5bfaca vmlinux.before
1624412 728710 3674856 6027978 5bfaca vmlinux.after
[akpm@osdl.org: topology.c fix]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Implement prof=sleep profiling. TASK_UNINTERRUPTIBLE sleeps will be taken
as a profile hit, and every millisecond spent sleeping causes a profile-hit
for the call site that initiated the sleep.
Sample readprofile output on i386:
306 ps2_sendbyte 1.3973
432 call_usermodehelper_keys 1.9548
484 ps2_command 0.6453
790 __driver_attach 4.7879
1593 msleep 44.2500
3976 sync_buffer 64.1290
4076 do_lookup 12.4648
8587 sync_page 122.6714
20820 total 0.0067
(NOTE: architectures need to check whether get_wchan() can be called from
deep within the wakeup path.)
akpm: we need to mark more functions __sched. lock_sock(), msleep(), others..
akpm: the contention in do_lookup() is a surprise. Presumably doing disk
reads for directory contents while holding i_mutex.
[akpm@osdl.org: various fixes]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add debug_show_held_locks(current) to __might_sleep() and schedule(); this
makes finding the offending lock leak easier.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Move process freezing functions from include/linux/sched.h to freezer.h, so
that modifications to the freezer or the kernel configuration don't require
recompiling just about everything.
[akpm@osdl.org: fix ueagle driver]
Signed-off-by: Nigel Cunningham <nigel@suspend2.net>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This likely profiling is pretty fun. I found a few possible problems
in sched.c.
This patch may be not measurable, but when I did measure long ago,
nooping (un)likely cost a couple of % on scheduler heavy benchmarks, so
it all adds up.
Tweak some branch hints:
- the 2nd 64 bits in the bitmask is likely to be populated, because it
contains the first 28 bits (nearly 3/4) of the normal priorities.
(ratio of 669669:691 ~= 1000:1).
- it isn't unlikely that context switching switches to another process. it
might be very rapidly switching to and from the idle process (ratio of
475815:419004 and 471330:423544). Let the branch predictor decide.
- preempt_enable seems to be very often called in a nested preempt_disable
or with interrupts disabled (ratio of 3567760:87965 ~= 40:1)
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Daniel Walker <dwalker@mvista.com>
Cc: Hua Zhong <hzhong@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
When the per cpu sched domains are build then they also need to be placed
on the node where the cpu resides otherwise we will have frequent off node
accesses which will slow down the system.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Up to now sched group's cpu_power for each sched domain is initialized
independently. This made the setup code ugly as the new sched domains are
getting added.
Make the sched group cpu_power setup code generic, by using domain child
field and new domain flag in sched_domain. For most of the sched
domains(except NUMA), sched group's cpu_power is now computed generically
using the domain properties of itself and of the child domain.
sched groups in NUMA domains are setup little differently and hence they
don't use this generic mechanism.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Introduce the child field in sched_domain struct and use it in
sched_balance_self().
We will also use this field in cleaning up the sched group cpu_power
setup(done in a different patch) code.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
If only a single CPU is present, printing this doesn't make much sense.
Signed-off-by: Dave Jones <davej@redhat.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove dynamic sched group allocations for MC and SMP domains. These
allocations can easily fail on big systems(1024 or so CPUs) and we can live
with out these dynamic allocations.
[akpm@osdl.org: build fix]
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Force /sbin/init off isolated cpus (unless every CPU is specified as an
isolcpu).
Users seem to think that the isolated CPUs shouldn't have much running on
them to begin with. That's fair enough: intuitive, I guess. It also means
that the cpu affinity masks of tasks will not include isolcpus by default,
which is also more intuitive, perhaps.
/sbin/init is spawned from the boot CPU's idle thread, and /sbin/init
starts the rest of userspace. So if the boot CPU is specified to be an
isolcpu, then prior to this patch, all of userspace will be run there.
(throw in a couple of plausible devinit -> cpuinit conversions I spotted
while we're here).
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Acked-by: Paul Jackson <pj@sgi.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
cpumask: ensure that the cpu_online_map and cpu_possible_map bitmasks, and
hence all the macros in <linux/cpumask.h> that require them, are available to
modules for all supported combinations of architecture and CONFIG_SMP.
Signed-off-by: Greg Banks <gnb@melbourne.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
There were a few accounting data/macros that are used in CSA but are #ifdef'ed
inside CONFIG_BSD_PROCESS_ACCT. This patch is to change those ifdef's from
CONFIG_BSD_PROCESS_ACCT to CONFIG_TASK_XACCT. A few defines are moved from
kernel/acct.c and include/linux/acct.h to kernel/tsacct.c and
include/linux/tsacct_kern.h.
Signed-off-by: Jay Lan <jlan@sgi.com>
Cc: Shailabh Nagar <nagar@watson.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Chris Sturtivant <csturtiv@sgi.com>
Cc: Tony Ernst <tee@sgi.com>
Cc: Guillaume Thouvenin <guillaume.thouvenin@bull.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I am not sure about this patch, I am asking Ingo to take a decision.
task_struct->state == EXIT_DEAD is a very special case, to avoid a confusion
it makes sense to introduce a new state, TASK_DEAD, while EXIT_DEAD should
live only in ->exit_state as documented in sched.h.
Note that this state is not visible to user-space, get_task_state() masks off
unsuitable states.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
schedule() checks PF_DEAD on every context switch and sets ->state = EXIT_DEAD
to ensure that the exiting task will be deactivated. Note that this EXIT_DEAD
is in fact a "random" value, we can use any bit except normal TASK_XXX values.
It is better to set this state in do_exit() along with PF_DEAD flag and remove
that check in schedule().
We are safe wrt concurrent try_to_wake_up() (for example ptrace, tkill), it
can not change task's ->state: the 'state' argument of try_to_wake_up() can't
have EXIT_DEAD bit. And in case when try_to_wake_up() sees a stale value of
->state == TASK_RUNNING it will do nothing.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I am not sure this patch is correct: I can't understand what the current
code does, and I don't know what it was supposed to do.
The comment says:
* can't change policy, except between SCHED_NORMAL
* and SCHED_BATCH:
The code:
if (((policy != SCHED_NORMAL && p->policy != SCHED_BATCH) &&
(policy != SCHED_BATCH && p->policy != SCHED_NORMAL)) &&
But this is equivalent to:
if ( (is_rt_policy(policy) && has_rt_policy(p)) &&
which means something different. We can't _decrease_ the current
->rt_priority with such a check (if rlim[RLIMIT_RTPRIO] == 0).
Probably, it was supposed to be:
if ( !(policy == SCHED_NORMAL && p->policy == SCHED_BATCH) &&
!(policy == SCHED_BATCH && p->policy == SCHED_NORMAL)
this matches the comment, but strange: it doesn't allow to _drop_ the
realtime priority when rlim[RLIMIT_RTPRIO] == 0.
I think the right check would be:
/* can't set/change rt policy */
if (is_rt_policy(policy) &&
policy != p->policy &&
!rlim_rtprio)
return -EPERM;
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Imho, makes the code a bit easier to read.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Spawing ksoftirqd, migration, or watchdog, and calling init_timers_cpu()
may fail with small memory. If it happens in initcalls, kernel NULL
pointer dereference happens later. This patch makes crash happen
immediately in such cases. It seems a bit better than getting kernel NULL
pointer dereference later.
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The scheduler will stop load balancing if the most busy processor contains
processes pinned via processor affinity.
The scheduler currently only does one search for busiest cpu. If it cannot
pull any tasks away from the busiest cpu because they were pinned then the
scheduler goes into a corner and sulks leaving the idle processors idle.
F.e. If you have processor 0 busy running four tasks pinned via taskset,
there are none on processor 1 and one just started two processes on
processor 2 then the scheduler will not move one of the two processes away
from processor 2.
This patch fixes that issue by forcing the scheduler to come out of its
corner and retrying the load balancing by considering other processors for
load balancing.
This patch was originally developed by John Hawkes and discussed at
http://marc.theaimsgroup.com/?l=linux-kernel&m=113901368523205&w=2.
I have removed extraneous material and gone back to equipping struct rq
with the cpu the queue is associated with since this makes the patch much
easier and it is likely that others in the future will have the same
difficulty of figuring out which processor owns which runqueue.
The overhead added through these patches is a single word on the stack if
the kernel is configured to support 32 cpus or less (32 bit). For 32 bit
environments the maximum number of cpus that can be configued is 255 which
would result in the use of 32 bytes additional on the stack. On IA64 up to
1k cpus can be configured which will result in the use of 128 additional
bytes on the stack. The maximum additional cache footprint is one
cacheline. Typically memory use will be much less than a cacheline and the
additional cpumask will be placed on the stack in a cacheline that already
contains other local variable.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: John Hawkes <hawkes@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
sched_setscheduler() looks at ->signal->rlim[]. It is unsafe do
dereference ->signal unless tasklist_lock or ->siglock is held (or p ==
current). We pin the task structure, but this can't prevent from
release_task()->__exit_signal() which sets ->signal = NULL.
Restore tasklist_lock across the setscheduler call.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initialize init task's pi_waiters plist. Otherwise cpu hotplug of cpu 0
might crash, since rt_mutex_getprio() accesses an uninitialized list head.
call chain which led to crash:
take_cpu_down
sched_idle_next
__setscheduler
rt_mutex_getprio
Using PLIST_HEAD_INIT in the INIT_TASK macro doesn't work unfortunately,
since the pi_waiters member is only conditionally present.
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In cond_resched_lock() it calls __resched_legal() before dropping the spin
lock. __resched_legal() will always finds the preempt_count non-zero and
will prevent the call to __cond_resched().
The attached patch adds a parameter to __resched_legal() with the expected
preempt_count value.
Cc: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Use the correct groups while initializing sched groups power for
allnodes_domain. This fixes the crash observed while creating exclusive
cpusets.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Reported-and-tested-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Make the task-related schedstats functions callable by delay accounting even
if schedstats collection isn't turned on. This removes the dependency of
delay accounting on schedstats.
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Balbir Singh <balbir@in.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Peter Chubb <peterc@gelato.unsw.edu.au>
Cc: Erich Focht <efocht@ess.nec.de>
Cc: Levent Serinol <lserinol@gmail.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Unlike earlier iterations of the delay accounting patches, now delays are only
collected for the actual I/O waits rather than try and cover the delays seen
in I/O submission paths.
Account separately for block I/O delays incurred as a result of swapin page
faults whose frequency can be affected by the task/process' rss limit. Hence
swapin delays can act as feedback for rss limit changes independent of I/O
priority changes.
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Balbir Singh <balbir@in.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Peter Chubb <peterc@gelato.unsw.edu.au>
Cc: Erich Focht <efocht@ess.nec.de>
Cc: Levent Serinol <lserinol@gmail.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
On platforms that have __ARCH_WANT_UNLOCKED_CTXSW set and want to implement
lock validator support there's a bug in rq->lock handling: in this case we
dont 'carry over' the runqueue lock into another task - but still we did a
spinlock_release() of it. Fix this by making the spinlock_release() in
context_switch() dependent on !__ARCH_WANT_UNLOCKED_CTXSW.
(Reported by Ralf Baechle on MIPS, which has __ARCH_WANT_UNLOCKED_CTXSW.
This fixes a lockdep-internal BUG message on such platforms.)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
- constify and optimize stat_nam (thanks to Michael Tokarev!)
- spelling and comment fixes
Signed-off-by: Andreas Mohr <andi@lisas.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Problem:
In the function __migrate_task(), deactivate_task() followed by
activate_task() is used to move the task from one run queue to
another. This has two undesirable effects:
1. The task's priority is recalculated. (Nowhere else in the
scheduler code is the priority recalculated for a change of CPU.)
2. The task's time stamp is set to the current time. At the very least,
this makes the adjustment of the time stamp before the call to
deactivate_task() redundant but I believe the problem is more serious
as the time stamp now holds the time of the queue change instead of
the time at which the task was woken. In addition, unless dest_rq is
the same queue as "current" is on the time stamp could be inaccurate
due to inter CPU drift.
Solution:
Replace the call to activate_task() with one to __activate_task().
Signed-off-by: Peter Williams <pwil3058@bigpond.net.au>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
convert:
- runqueue_t to 'struct rq'
- prio_array_t to 'struct prio_array'
- migration_req_t to 'struct migration_req'
I was the one who added these but they are both against the kernel coding
style and also were used inconsistently at places. So just get rid of them at
once, now that we are flushing the scheduler patch-queue anyway.
Conversion was mostly scripted, the result was reviewed and all secondary
whitespace and style impact (if any) was fixed up by hand.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
cleanup: remove task_t and convert all the uses to struct task_struct. I
introduced it for the scheduler anno and it was a mistake.
Conversion was mostly scripted, the result was reviewed and all
secondary whitespace and style impact (if any) was fixed up by hand.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Clean up some of the impact of recent (and not so recent) scheduler
changes:
- turning macros into nice inline functions
- sanitizing and unifying variable definitions
- whitespace, style consistency, 80-lines, comment correctness, spelling
and curly braces police
Due to the macro hell and variable placement simplifications there's even 26
bytes of .text saved:
text data bss dec hex filename
25510 4153 192 29855 749f sched.o.before
25484 4153 192 29829 7485 sched.o.after
[akpm@osdl.org: build fix]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Teach per-CPU runqueue locks and recursive locking code to the lock validator.
Has no effect on non-lockdep kernels.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Use the lock validator framework to prove spinlock and rwlock locking
correctness.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Accurate hard-IRQ-flags and softirq-flags state tracing.
This allows us to attach extra functionality to IRQ flags on/off
events (such as trace-on/off).
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Generic lock debugging:
- generalized lock debugging framework. For example, a bug in one lock
subsystem turns off debugging in all lock subsystems.
- got rid of the caller address passing (__IP__/__IP_DECL__/etc.) from
the mutex/rtmutex debugging code: it caused way too much prototype
hackery, and lockdep will give the same information anyway.
- ability to do silent tests
- check lock freeing in vfree too.
- more finegrained debugging options, to allow distributions to
turn off more expensive debugging features.
There's no separate 'held mutexes' list anymore - but there's a 'held locks'
stack within lockdep, which unifies deadlock detection across all lock
classes. (this is independent of the lockdep validation stuff - lockdep first
checks whether we are holding a lock already)
Here are the current debugging options:
CONFIG_DEBUG_MUTEXES=y
CONFIG_DEBUG_LOCK_ALLOC=y
which do:
config DEBUG_MUTEXES
bool "Mutex debugging, basic checks"
config DEBUG_LOCK_ALLOC
bool "Detect incorrect freeing of live mutexes"
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Fix a bug identified by Zou Nan hai <nanhai.zou@intel.com>:
If the system is in state SYSTEM_BOOTING, and need_resched() is true,
cond_resched() returns true even though it didn't reschedule. Consequently
need_resched() remains true and JBD locks up.
Fix that by teaching cond_resched() to only return true if it really did call
schedule().
cond_resched_lock() and cond_resched_softirq() have a problem too. If we're
in SYSTEM_BOOTING state and need_resched() is true, these functions will drop
the lock and will then try to call schedule(), but the SYSTEM_BOOTING state
will prevent schedule() from being called. So on return, need_resched() will
still be true, but cond_resched_lock() has to return 1 to tell the caller that
the lock was dropped. The caller will probably lock up.
Bottom line: if these functions dropped the lock, they _must_ call schedule()
to clear need_resched(). Make it so.
Also, uninline __cond_resched(). It's largeish, and slowpath.
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
When the priority of a task, which is blocked on a lock, changes we must
propagate this change into the PI lock chain. Therefor the chain walk code
is changed to get rid of the references to current to avoid false positives
in the deadlock detector, as setscheduler might be called by a task which
holds the lock on which the task whose priority is changed is blocked.
Also add some comments about the get/put_task_struct usage to avoid
confusion.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
There is no need to hold tasklist_lock across the setscheduler call, when
we pin the task structure with get_task_struct(). Interrupts are disabled
in setscheduler anyway and the permission checks do not need interrupts
disabled.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add framework to boost/unboost the priority of RT tasks.
This consists of:
- caching the 'normal' priority in ->normal_prio
- providing a functions to set/get the priority of the task
- make sched_setscheduler() aware of boosting
The effective_prio() cleanups also fix a priority-calculation bug pointed out
by Andrey Gelman, in set_user_nice().
has_rt_policy() fix: Peter Williams <pwil3058@bigpond.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Andrey Gelman <agelman@012.net.il>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Thomas Gleixner is adding the call to a rtmutex function in setscheduler.
This call grabs a spin_lock that is not always protected by interrupts
disabled. So this means that setscheduler cant be called from interrupt
context.
To prevent this from happening in the future, this patch adds a
BUG_ON(in_interrupt()) in that function. (Thanks to akpm <aka. Andrew
Morton> for this suggestion).
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
sysfs entries 'sched_mc_power_savings' and 'sched_smt_power_savings' in
/sys/devices/system/cpu/ control the MC/SMT power savings policy for the
scheduler.
Based on the values (1-enable, 0-disable) for these controls, sched groups
cpu power will be determined for different domains. When power savings
policy is enabled and under light load conditions, scheduler will minimize
the physical packages/cpu cores carrying the load and thus conserving
power(with a perf impact based on the workload characteristics... see OLS
2005 CMP kernel scheduler paper for more details..)
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Con Kolivas <kernel@kolivas.org>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
As explained here:
http://marc.theaimsgroup.com/?l=linux-kernel&m=114327539012323&w=2
there is a problem with sharing sched_group structures between two
separate sched_group structures for different sched_domains.
The patch has been tested and found to avoid the kernel lockup problem
described in above URL.
Signed-off-by: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The sched group structures used to represent various nodes need to be
allocated from respective nodes (as suggested here also:
http://uwsg.ucs.indiana.edu/hypermail/linux/kernel/0603.3/0051.html)
Signed-off-by: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Try to handle mem allocation failures in build_sched_domains by bailing out
and cleaning up thus-far allocated memory. The patch has a direct consequence
that we disable load balancing completely (even at sibling level) upon *any*
memory allocation failure.
[Lee.Schermerhorn@hp.com: bugfix]
Signed-off-by: Srivatsa Vaddagir <vatsa@in.ibm.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Problem:
To help distribute high priority tasks evenly across the available CPUs
move_tasks() does not, under some circumstances, skip tasks whose load
weight is bigger than the designated amount. Because the highest priority
task on the busiest queue may be on the expired array it may be moved as a
result of this mechanism. Apart from not being the most desirable way to
redistribute the high priority tasks (we'd rather move the second highest
priority task), there is a risk that this could set up a loop with this
task bouncing backwards and forwards between the two queues. (This latter
possibility can be demonstrated by running a nice==-20 CPU bound task on an
otherwise quiet 2 CPU system.)
Solution:
Modify the mechanism so that it does not override skip for the highest
priority task on the CPU. Of course, if there are more than one tasks at
the highest priority then it will allow the override for one of them as
this is a desirable redistribution of high priority tasks.
Signed-off-by: Peter Williams <pwil3058@bigpond.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Problem:
The move_tasks() function is designed to move UP TO the amount of load it
is asked to move and in doing this it skips over tasks looking for ones
whose load weights are less than or equal to the remaining load to be
moved. This is (in general) a good thing but it has the unfortunate result
of breaking one of the original load balancer's good points: namely, that
(within the limits imposed by the active/expired array model and the fact
the expired is processed first) it moves high priority tasks before low
priority ones and this means there's a good chance (see active/expired
problem for why it's only a chance) that the highest priority task on the
queue but not actually on the CPU will be moved to the other CPU where (as
a high priority task) it may preempt the current task.
Solution:
Modify move_tasks() so that high priority tasks are not skipped when moving
them will make them the highest priority task on their new run queue.
Signed-off-by: Peter Williams <pwil3058@bigpond.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Problem:
The introduction of separate run queues per CPU has brought with it "nice"
enforcement problems that are best described by a simple example.
For the sake of argument suppose that on a single CPU machine with a
nice==19 hard spinner and a nice==0 hard spinner running that the nice==0
task gets 95% of the CPU and the nice==19 task gets 5% of the CPU. Now
suppose that there is a system with 2 CPUs and 2 nice==19 hard spinners and
2 nice==0 hard spinners running. The user of this system would be entitled
to expect that the nice==0 tasks each get 95% of a CPU and the nice==19
tasks only get 5% each. However, whether this expectation is met is pretty
much down to luck as there are four equally likely distributions of the
tasks to the CPUs that the load balancing code will consider to be balanced
with loads of 2.0 for each CPU. Two of these distributions involve one
nice==0 and one nice==19 task per CPU and in these circumstances the users
expectations will be met. The other two distributions both involve both
nice==0 tasks being on one CPU and both nice==19 being on the other CPU and
each task will get 50% of a CPU and the user's expectations will not be
met.
Solution:
The solution to this problem that is implemented in the attached patch is
to use weighted loads when determining if the system is balanced and, when
an imbalance is detected, to move an amount of weighted load between run
queues (as opposed to a number of tasks) to restore the balance. Once
again, the easiest way to explain why both of these measures are necessary
is to use a simple example. Suppose that (in a slight variation of the
above example) that we have a two CPU system with 4 nice==0 and 4 nice=19
hard spinning tasks running and that the 4 nice==0 tasks are on one CPU and
the 4 nice==19 tasks are on the other CPU. The weighted loads for the two
CPUs would be 4.0 and 0.2 respectively and the load balancing code would
move 2 tasks resulting in one CPU with a load of 2.0 and the other with
load of 2.2. If this was considered to be a big enough imbalance to
justify moving a task and that task was moved using the current
move_tasks() then it would move the highest priority task that it found and
this would result in one CPU with a load of 3.0 and the other with a load
of 1.2 which would result in the movement of a task in the opposite
direction and so on -- infinite loop. If, on the other hand, an amount of
load to be moved is calculated from the imbalance (in this case 0.1) and
move_tasks() skips tasks until it find ones whose contributions to the
weighted load are less than this amount it would move two of the nice==19
tasks resulting in a system with 2 nice==0 and 2 nice=19 on each CPU with
loads of 2.1 for each CPU.
One of the advantages of this mechanism is that on a system where all tasks
have nice==0 the load balancing calculations would be mathematically
identical to the current load balancing code.
Notes:
struct task_struct:
has a new field load_weight which (in a trade off of space for speed)
stores the contribution that this task makes to a CPU's weighted load when
it is runnable.
struct runqueue:
has a new field raw_weighted_load which is the sum of the load_weight
values for the currently runnable tasks on this run queue. This field
always needs to be updated when nr_running is updated so two new inline
functions inc_nr_running() and dec_nr_running() have been created to make
sure that this happens. This also offers a convenient way to optimize away
this part of the smpnice mechanism when CONFIG_SMP is not defined.
int try_to_wake_up():
in this function the value SCHED_LOAD_BALANCE is used to represent the load
contribution of a single task in various calculations in the code that
decides which CPU to put the waking task on. While this would be a valid
on a system where the nice values for the runnable tasks were distributed
evenly around zero it will lead to anomalous load balancing if the
distribution is skewed in either direction. To overcome this problem
SCHED_LOAD_SCALE has been replaced by the load_weight for the relevant task
or by the average load_weight per task for the queue in question (as
appropriate).
int move_tasks():
The modifications to this function were complicated by the fact that
active_load_balance() uses it to move exactly one task without checking
whether an imbalance actually exists. This precluded the simple
overloading of max_nr_move with max_load_move and necessitated the addition
of the latter as an extra argument to the function. The internal
implementation is then modified to move up to max_nr_move tasks and
max_load_move of weighted load. This slightly complicates the code where
move_tasks() is called and if ever active_load_balance() is changed to not
use move_tasks() the implementation of move_tasks() should be simplified
accordingly.
struct sched_group *find_busiest_group():
Similar to try_to_wake_up(), there are places in this function where
SCHED_LOAD_SCALE is used to represent the load contribution of a single
task and the same issues are created. A similar solution is adopted except
that it is now the average per task contribution to a group's load (as
opposed to a run queue) that is required. As this value is not directly
available from the group it is calculated on the fly as the queues in the
groups are visited when determining the busiest group.
A key change to this function is that it is no longer to scale down
*imbalance on exit as move_tasks() uses the load in its scaled form.
void set_user_nice():
has been modified to update the task's load_weight field when it's nice
value and also to ensure that its run queue's raw_weighted_load field is
updated if it was runnable.
From: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
With smpnice, sched groups with highest priority tasks can mask the imbalance
between the other sched groups with in the same domain. This patch fixes some
of the listed down scenarios by not considering the sched groups which are
lightly loaded.
a) on a simple 4-way MP system, if we have one high priority and 4 normal
priority tasks, with smpnice we would like to see the high priority task
scheduled on one cpu, two other cpus getting one normal task each and the
fourth cpu getting the remaining two normal tasks. but with current
smpnice extra normal priority task keeps jumping from one cpu to another
cpu having the normal priority task. This is because of the
busiest_has_loaded_cpus, nr_loaded_cpus logic.. We are not including the
cpu with high priority task in max_load calculations but including that in
total and avg_load calcuations.. leading to max_load < avg_load and load
balance between cpus running normal priority tasks(2 Vs 1) will always show
imbalanace as one normal priority and the extra normal priority task will
keep moving from one cpu to another cpu having normal priority task..
b) 4-way system with HT (8 logical processors). Package-P0 T0 has a
highest priority task, T1 is idle. Package-P1 Both T0 and T1 have 1 normal
priority task each.. P2 and P3 are idle. With this patch, one of the
normal priority tasks on P1 will be moved to P2 or P3..
c) With the current weighted smp nice calculations, it doesn't always make
sense to look at the highest weighted runqueue in the busy group..
Consider a load balance scenario on a DP with HT system, with Package-0
containing one high priority and one low priority, Package-1 containing one
low priority(with other thread being idle).. Package-1 thinks that it need
to take the low priority thread from Package-0. And find_busiest_queue()
returns the cpu thread with highest priority task.. And ultimately(with
help of active load balance) we move high priority task to Package-1. And
same continues with Package-0 now, moving high priority task from package-1
to package-0.. Even without the presence of active load balance, load
balance will fail to balance the above scenario.. Fix find_busiest_queue
to use "imbalance" when it is lightly loaded.
[kernel@kolivas.org: sched: store weighted load on up]
[kernel@kolivas.org: sched: add discrete weighted cpu load function]
[suresh.b.siddha@intel.com: sched: remove dead code]
Signed-off-by: Peter Williams <pwil3058@bigpond.com.au>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Cc: John Hawkes <hawkes@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
There is a race between set_cpus_allowed() and move_task_off_dead_cpu().
__migrate_task() doesn't report any err code, so task can be left on its
runqueue if its cpus_allowed mask changed so that dest_cpu is not longer a
possible target. Also, chaning cpus_allowed mask requires rq->lock being
held.
Signed-off-by: Kirill Korotaev <dev@openvz.org>
Acked-By: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Unless we expect to have more than 2G CPUs, there's no reason to have 'i'
as a long long here.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The relationship between INTERACTIVE_SLEEP and the ceiling is not perfect
and not explicit enough. The sleep boost is not supposed to be any larger
than without this code and the comment is not clear enough about what
exactly it does, just the reason it does it. Fix it.
There is a ceiling to the priority beyond which tasks that only ever sleep
for very long periods cannot surpass. Fix it.
Prevent the on-runqueue bonus logic from defeating the idle sleep logic.
Opportunity to micro-optimise.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial report and lock contention fix from Chris Mason:
Recent benchmarks showed some performance regressions between 2.6.16 and
2.6.5. We tracked down one of the regressions to lock contention in
schedule heavy workloads (~70,000 context switches per second)
kernel/sched.c:dependent_sleeper() was responsible for most of the lock
contention, hammering on the run queue locks. The patch below is more of a
discussion point than a suggested fix (although it does reduce lock
contention significantly). The dependent_sleeper code looks very expensive
to me, especially for using a spinlock to bounce control between two
different siblings in the same cpu.
It is further optimized:
* perform dependent_sleeper check after next task is determined
* convert wake_sleeping_dependent to use trylock
* skip smt runqueue check if trylock fails
* optimize double_rq_lock now that smt nice is converted to trylock
* early exit in searching first SD_SHARE_CPUPOWER domain
* speedup fast path of dependent_sleeper
[akpm@osdl.org: cleanup]
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Con Kolivas <kernel@kolivas.org>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Chris Mason <mason@suse.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Make notifier_calls associated with cpu_notifier as __cpuinit.
__cpuinit makes sure that the function is init time only unless
CONFIG_HOTPLUG_CPU is defined.
[akpm@osdl.org: section fix]
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
During some profiling I noticed that default_idle causes a lot of
memory traffic. I think that is caused by the atomic operations
to clear/set the polling flag in thread_info. There is actually
no reason to make this atomic - only the idle thread does it
to itself, other CPUs only read it. So I moved it into ti->status.
Converted i386/x86-64/ia64 for now because that was the easiest
way to fix ACPI which also manipulates these flags in its idle
function.
Cc: Nick Piggin <npiggin@novell.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Len Brown <len.brown@intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The introduction of SCHED_BATCH scheduling class with a value of 3 means
that the expression (p->policy & SCHED_FIFO) will return true if policy
is SCHED_BATCH or SCHED_FIFO.
Unfortunately, this expression is used in sys_sched_rr_get_interval()
and in the absence of a comment to say that this is intentional I
presume that it is unintentional and erroneous.
The fix is to change the expression to (p->policy == SCHED_FIFO).
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
If a cpu hotplug callback fails on CPU_UP_PREPARE, all callbacks will be
called with CPU_UP_CANCELED. A few of these callbacks assume that on
CPU_UP_PREPARE a pointer to task has been stored in a percpu array. This
assumption is not true if CPU_UP_PREPARE fails and the following calls to
kthread_bind() in CPU_UP_CANCELED will cause an addressing exception
because of passing a NULL pointer.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
There are several instances of per_cpu(foo, raw_smp_processor_id()), which
is semantically equivalent to __get_cpu_var(foo) but without the warning
that smp_processor_id() can give if CONFIG_DEBUG_PREEMPT is enabled. For
those architectures with optimized per-cpu implementations, namely ia64,
powerpc, s390, sparc64 and x86_64, per_cpu() turns into more and slower
code than __get_cpu_var(), so it would be preferable to use __get_cpu_var
on those platforms.
This defines a __raw_get_cpu_var(x) macro which turns into per_cpu(x,
raw_smp_processor_id()) on architectures that use the generic per-cpu
implementation, and turns into __get_cpu_var(x) on the architectures that
have an optimized per-cpu implementation.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
add the __might_sleep() check back to cond_resched().
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch adds LSM hooks into the setaffinity and getaffinity functions to
enable security modules to control these operations between tasks with
task_setscheduler and task_getscheduler LSM hooks.
Signed-off-by: David Quigley <dpquigl@tycho.nsa.gov>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This reverts commit 5ce74abe78 (and its
dependent commit 8a5bc075b8), because of
audio underruns.
Reported by Rene Herman <rene.herman@keyaccess.nl>, who also pinpointed
the exact cause of the underruns:
"Audio underruns galore, with only ogg123 and firefox (browsing the
GIT tree online is also a nice trigger by the way).
If I back it out, everything is fine for me again."
Cc: Rene Herman <rene.herman@keyaccess.nl>
Cc: Mike Galbraith <efault@gmx.de>
Acked-by: Con Kolivas <kernel@kolivas.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Few of the notifier_chain_register() callers use __devinitdata in the
definition of notifier_block data structure. It is incorrect as the
data structure should be available after the initializations (they do
not unregister them during initializations).
This was leading to an oops when notifier_chain_register() call is
invoked for those callback chains after initialization.
This patch fixes all such usages to _not_ have the notifier_block data
structure in the init data section.
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
RT tasks are being awakened on the expired array when expired_starving() is
true, whereas they really should be excluded. Fix.
Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Con Kolivas <kernel@kolivas.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Fix a starvation problem that occurs when a stream of highly interactive tasks
delay an array switch for extended periods despite EXPIRED_STARVING(rq) being
true. AFAIKT, the only choice is to enqueue awakening tasks on the expired
array in this case.
Without this patch, it can be nearly impossible to remotely login to a busy
server, and interactive shell commands can starve for minutes.
Also, convert the EXPIRED_STARVING macro into an inline function which humans
can understand.
Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Acked-by: Con Kolivas <kernel@kolivas.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
To increase the strength of SCHED_BATCH as a scheduling hint we can
activate batch tasks on the expired array since by definition they are
latency insensitive tasks.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
On runqueue time is used to elevate priority in schedule().
In the code it currently requeues tasks even if their priority is not
elevated, which would end up placing them at the end of their runqueue
array effectively delaying them instead of improving their priority.
Bug spotted by Mike Galbraith <efault@gmx.de>
This patch removes this requeueing.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Tasks waiting in SLEEP_NONINTERACTIVE state can now get to best priority so
they need to be included in the idle detection code.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
We watch for tasks that sleep extended periods and don't allow one single
prolonged sleep period from elevating priority to maximum bonus to prevent cpu
bound tasks from getting high priority with single long sleeps. There is a
bug in the current code that also penalises tasks that already have high
priority. Correct that bug.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Alterations to the pipe code in the kernel made it possible for relative
starvation to occur with tasks that slept waiting on a pipe getting unfair
priority bonuses even if they were otherwise fully cpu bound so the
TASK_NONINTERACTIVE flag was introduced which prevented any change to
sleep_avg while sleeping waiting on a pipe. This change also leads to the
converse though, preventing any priority boost from occurring in truly
interactive tasks that wait on pipes.
Convert the TASK_NONINTERACTIVE flag to set sleep_type to SLEEP_NONINTERACTIVE
which will allow a linear bonus to priority based on sleep time thus allowing
interactive tasks to get high priority if they sleep enough.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The activated flag in task_struct is used to track different sleep types and
its usage is somewhat obfuscated. Convert the variable to an enum with more
descriptive names without altering the function.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Currently, count_active_tasks() calls both nr_running() &
nr_interruptible(). Each of these functions does a "for_each_cpu" & reads
values from the runqueue of each cpu. Although this is not a lot of
instructions, each runqueue may be located on different node. Depending on
the architecture, a unique TLB entry may be required to access each
runqueue.
Since there may be more runqueues than cpu TLB entries, a scan of all
runqueues can trash the TLB. Each memory reference incurs a TLB miss &
refill.
In addition, the runqueue cacheline that contains nr_running &
nr_uninterruptible may be evicted from the cache between the two passes.
This causes unnecessary cache misses.
Combining nr_running() & nr_interruptible() into a single function
substantially reduces the TLB & cache misses on large systems. This should
have no measureable effect on smaller systems.
On a 128p IA64 system running a memory stress workload, the new function
reduced the overhead of calc_load() from 605 usec/call to 324 usec/call.
Signed-off-by: Jack Steiner <steiner@sgi.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Current sched groups power calculation for allnodes_domains is wrong. We
should really be using cumulative power of the physical packages in that
group (similar to the calculation in node_domains)
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add a new sched domain for representing multi-core with shared caches
between cores. Consider a dual package system, each package containing two
cores and with last level cache shared between cores with in a package. If
there are two runnable processes, with this appended patch those two
processes will be scheduled on different packages.
On such systems, with this patch we have observed 8% perf improvement with
specJBB(2 warehouse) benchmark and 35% improvement with CFP2000 rate(with 2
users).
This new domain will come into play only on multi-core systems with shared
caches. On other systems, this sched domain will be removed by domain
degeneration code. This new domain can be also used for implementing power
savings policy (see OLS 2005 CMP kernel scheduler paper for more details..
I will post another patch for power savings policy soon)
Most of the arch/* file changes are for cpu_coregroup_map() implementation.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
When kretprobe probes the schedule() function, if the probed process exits
then schedule() will never return, so some kretprobe instances will never
be recycled.
In this patch the parent process will recycle retprobe instances of the
probed function and there will be no memory leak of kretprobe instances.
Signed-off-by: bibo mao <bibo.mao@intel.com>
Cc: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Consolidate all kernel bug printouts to begin with the "BUG: " string.
Makes it easier to find them in large bootup logs.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
We have noticed lockups during boot when stress testing kexec on ppc64.
Two cpus would deadlock in scheduler code trying to grab already taken
spinlocks.
The double_rq_lock code uses the address of the runqueue to order the
taking of multiple locks. This address is a per cpu variable:
if (rq1 < rq2) {
spin_lock(&rq1->lock);
spin_lock(&rq2->lock);
} else {
spin_lock(&rq2->lock);
spin_lock(&rq1->lock);
}
On the other hand, the code in wake_sleeping_dependent uses the cpu id
order to grab locks:
for_each_cpu_mask(i, sibling_map)
spin_lock(&cpu_rq(i)->lock);
This means we rely on the address of per cpu data increasing as cpu ids
increase. While this will be true for the generic percpu implementation it
may not be true for arch specific implementations.
One way to solve this is to always take runqueues in cpu id order. To do
this we add a cpu variable to the runqueue and check it in the
double runqueue locking functions.
Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove the sleep_avg multiplier. This multiplier was necessary back when
we had 10 seconds of dynamic range in sleep_avg, but now that we only have
one second, it causes that one second to be compressed down to 100ms in
some cases. This is particularly noticeable when compiling a kernel in a
slow NFS mount, and I believe it to be a very likely candidate for other
recently reported network related interactivity problems.
In testing, I can detect no negative impact of this removal.
Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The patch '[PATCH] RCU signal handling' [1] added an export for
__put_task_struct_cb, a put_task_struct helper newly introduced in that
patch. But the put_task_struct couldn't be used modular previously as
__put_task_struct wasn't exported. There are not callers of it in modular
code, and it shouldn't be exported because we don't want drivers to hold
references to task_structs.
This patch removes the export and folds __put_task_struct into
__put_task_struct_cb as there's no other caller.
[1] http://www2.kernel.org/git/gitweb.cgi?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=e56d090310d7625ecb43a1eeebd479f04affb48b
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Idle threads should have a sane ->timestamp value, to avoid init kernel
thread(s) from inheriting it and causing miscalculations in
try_to_wake_up().
Reported-by: Mike Galbraith <efault@gmx.de>.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Just to be safe, we should not trigger a conditional reschedule during
the early boot sequence. We've historically done some questionable
early on, and the safety warnings in __might_sleep() are generally
turned off during that period, so there might be problems lurking.
This affects CONFIG_PREEMPT_VOLUNTARY, which takes over might_sleep() to
cause a voluntary conditional reschedule.
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Heiko Carstens <heiko.carstens@de.ibm.com> wrote:
The boot sequence on s390 sometimes takes ages and we spend a very long
time (up to one or two minutes) in calibrate_migration_costs. The time
spent there differs from boot to boot. Also the calculated costs differ
a lot. I've seen differences by up to a factor of 15 (yes, factor not
percent). Also I doubt that making these measurements make much sense on
a completely virtualized architecture where you cannot tell how much cpu
time you will get anyway.
So introduce the CONFIG_DEFAULT_MIGRATION_COST method for an architecture
to set the scheduler migration costs. This turns off automatic detection
of migration costs. Makes sense on virtual platforms, where migration
costs are hard to measure accurately.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Revert commit d7102e95b7b9c00277562c29aad421d2d521c5f6:
[PATCH] sched: filter affine wakeups
Apparently caused more than 10% performance regression for aim7 benchmark.
The setup in use is 16-cpu HP rx8620, 64Gb of memory and 12 MSA1000s with 144
disks. Each disk is 72Gb with a single ext3 filesystem (courtesy of HP, who
supplied benchmark results).
The problem is, for aim7, the wake-up pattern is random, but it still needs
load balancing action in the wake-up path to achieve best performance. With
the above commit, lack of load balancing hurts that workload.
However, for workloads like database transaction processing, the requirement
is exactly opposite. In the wake up path, best performance is achieved with
absolutely zero load balancing. We simply wake up the process on the CPU that
it was previously run. Worst performance is obtained when we do load
balancing at wake up.
There isn't an easy way to auto detect the workload characteristics. Ingo's
earlier patch that detects idle CPU and decide whether to load balance or not
doesn't perform with aim7 either since all CPUs are busy (it causes even
bigger perf. regression).
Revert commit d7102e95b7, which causes more
than 10% performance regression with aim7.
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I don't think the code is quite ready, which is why I asked for Peter's
additions to also be merged before I acked it (although it turned out that
it still isn't quite ready with his additions either).
Basically I have had similar observations to Suresh in that it does not
play nicely with the rest of the balancing infrastructure (and raised
similar concerns in my review).
The samples (group of 4) I got for "maximum recorded imbalance" on a 2x2
SMP+HT Xeon are as follows:
| Following boot | hackbench 20 | hackbench 40
-----------+----------------+---------------------+---------------------
2.6.16-rc2 | 30,37,100,112 | 5600,5530,6020,6090 | 6390,7090,8760,8470
+nosmpnice | 3, 2, 4, 2 | 28, 150, 294, 132 | 348, 348, 294, 347
Hackbench raw performance is down around 15% with smpnice (but that in
itself isn't a huge deal because it is just a benchmark). However, the
samples show that the imbalance passed into move_tasks is increased by
about a factor of 10-30. I think this would also go some way to explaining
latency blips turning up in the balancing code (though I haven't actually
measured that).
We'll probably have to revert this in the SUSE kernel.
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: "Martin J. Bligh" <mbligh@aracnet.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
migration_cost prints after every CPU hotplug event. Make it print only
once at boot.
Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
percpu_data blindly allocates bootmem memory to store NR_CPUS instances of
cpudata, instead of allocating memory only for possible cpus.
As a preparation for changing that, we need to convert various 0 -> NR_CPUS
loops to use for_each_cpu().
(The above only applies to users of asm-generic/percpu.h. powerpc has gone it
alone and is presently only allocating memory for present CPUs, so it's
currently corrupting memory).
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Jens Axboe <axboe@suse.de>
Cc: Anton Blanchard <anton@samba.org>
Acked-by: William Irwin <wli@holomorphy.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Change sched_getaffinity() so that it returns a bitmap that indicates the
legally schedulable cpus that a task is allowed to run on.
Without this patch, if CONFIG_HOTPLUG_CPU is enabled, sched_getaffinity()
unconditionally returns (at least on IA64) a mask with NR_CPUS bits set.
This conveys no useful infornmation except for a kernel compile option.
This fixes a breakage we obseved running recent kernels. We have MPI jobs
that use sched_getaffinity() to determine where to place their threads.
Placing them on non-existant cpus is problematic :-)
Signed-off-by: Jack Steiner <steiner@sgi.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Nathan Lynch <ntl@pobox.com>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This reduces the amount of time the migration cost calculations cost
during bootup. Based on numbers by Tony Luck <tony.luck@intel.com>.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Currently, a negative policy argument passed into the
'sys_sched_setscheduler()' system call, will return with success. However,
the manpage for 'sys_sched_setscheduler' says:
EINVAL The scheduling policy is not one of the recognized policies, or the
parameter p does not make sense for the policy.
Signed-off-by: Jason Baron <jbaron@redhat.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove the "inline" keyword from a bunch of big functions in the kernel with
the goal of shrinking it by 30kb to 40kb
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add a new SCHED_BATCH (3) scheduling policy: such tasks are presumed
CPU-intensive, and will acquire a constant +5 priority level penalty. Such
policy is nice for workloads that are non-interactive, but which do not
want to give up their nice levels. The policy is also useful for workloads
that want a deterministic scheduling policy without interactivity causing
extra preemptions (between that workload's tasks).
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
)
From: Nick Piggin <nickpiggin@yahoo.com.au>
Track the last waker CPU, and only consider wakeup-balancing if there's a
match between current waker CPU and the previous waker CPU. This ensures
that there is some correlation between two subsequent wakeup events before
we move the task. Should help random-wakeup workloads on large SMP
systems, by reducing the migration attempts by a factor of nr_cpus.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
)
From: Ingo Molnar <mingo@elte.hu>
This is the latest version of the scheduler cache-hot-auto-tune patch.
The first problem was that detection time scaled with O(N^2), which is
unacceptable on larger SMP and NUMA systems. To solve this:
- I've added a 'domain distance' function, which is used to cache
measurement results. Each distance is only measured once. This means
that e.g. on NUMA distances of 0, 1 and 2 might be measured, on HT
distances 0 and 1, and on SMP distance 0 is measured. The code walks
the domain tree to determine the distance, so it automatically follows
whatever hierarchy an architecture sets up. This cuts down on the boot
time significantly and removes the O(N^2) limit. The only assumption
is that migration costs can be expressed as a function of domain
distance - this covers the overwhelming majority of existing systems,
and is a good guess even for more assymetric systems.
[ People hacking systems that have assymetries that break this
assumption (e.g. different CPU speeds) should experiment a bit with
the cpu_distance() function. Adding a ->migration_distance factor to
the domain structure would be one possible solution - but lets first
see the problem systems, if they exist at all. Lets not overdesign. ]
Another problem was that only a single cache-size was used for measuring
the cost of migration, and most architectures didnt set that variable
up. Furthermore, a single cache-size does not fit NUMA hierarchies with
L3 caches and does not fit HT setups, where different CPUs will often
have different 'effective cache sizes'. To solve this problem:
- Instead of relying on a single cache-size provided by the platform and
sticking to it, the code now auto-detects the 'effective migration
cost' between two measured CPUs, via iterating through a wide range of
cachesizes. The code searches for the maximum migration cost, which
occurs when the working set of the test-workload falls just below the
'effective cache size'. I.e. real-life optimized search is done for
the maximum migration cost, between two real CPUs.
This, amongst other things, has the positive effect hat if e.g. two
CPUs share a L2/L3 cache, a different (and accurate) migration cost
will be found than between two CPUs on the same system that dont share
any caches.
(The reliable measurement of migration costs is tricky - see the source
for details.)
Furthermore i've added various boot-time options to override/tune
migration behavior.
Firstly, there's a blanket override for autodetection:
migration_cost=1000,2000,3000
will override the depth 0/1/2 values with 1msec/2msec/3msec values.
Secondly, there's a global factor that can be used to increase (or
decrease) the autodetected values:
migration_factor=120
will increase the autodetected values by 20%. This option is useful to
tune things in a workload-dependent way - e.g. if a workload is
cache-insensitive then CPU utilization can be maximized by specifying
migration_factor=0.
I've tested the autodetection code quite extensively on x86, on 3
P3/Xeon/2MB, and the autodetected values look pretty good:
Dual Celeron (128K L2 cache):
---------------------
migration cost matrix (max_cache_size: 131072, cpu: 467 MHz):
---------------------
[00] [01]
[00]: - 1.7(1)
[01]: 1.7(1) -
---------------------
cacheflush times [2]: 0.0 (0) 1.7 (1784008)
---------------------
Here the slow memory subsystem dominates system performance, and even
though caches are small, the migration cost is 1.7 msecs.
Dual HT P4 (512K L2 cache):
---------------------
migration cost matrix (max_cache_size: 524288, cpu: 2379 MHz):
---------------------
[00] [01] [02] [03]
[00]: - 0.4(1) 0.0(0) 0.4(1)
[01]: 0.4(1) - 0.4(1) 0.0(0)
[02]: 0.0(0) 0.4(1) - 0.4(1)
[03]: 0.4(1) 0.0(0) 0.4(1) -
---------------------
cacheflush times [2]: 0.0 (33900) 0.4 (448514)
---------------------
Here it can be seen that there is no migration cost between two HT
siblings (CPU#0/2 and CPU#1/3 are separate physical CPUs). A fast memory
system makes inter-physical-CPU migration pretty cheap: 0.4 msecs.
8-way P3/Xeon [2MB L2 cache]:
---------------------
migration cost matrix (max_cache_size: 2097152, cpu: 700 MHz):
---------------------
[00] [01] [02] [03] [04] [05] [06] [07]
[00]: - 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)
[01]: 19.2(1) - 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)
[02]: 19.2(1) 19.2(1) - 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1)
[03]: 19.2(1) 19.2(1) 19.2(1) - 19.2(1) 19.2(1) 19.2(1) 19.2(1)
[04]: 19.2(1) 19.2(1) 19.2(1) 19.2(1) - 19.2(1) 19.2(1) 19.2(1)
[05]: 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) - 19.2(1) 19.2(1)
[06]: 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) - 19.2(1)
[07]: 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) 19.2(1) -
---------------------
cacheflush times [2]: 0.0 (0) 19.2 (19281756)
---------------------
This one has huge caches and a relatively slow memory subsystem - so the
migration cost is 19 msecs.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Cc: <wilder@us.ibm.com>
Signed-off-by: John Hawkes <hawkes@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
They are referred to often so avoid potential false sharing for them.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
- Move capable() from sched.h to capability.h;
- Use <linux/capability.h> where capable() is used
(in include/, block/, ipc/, kernel/, a few drivers/,
mm/, security/, & sound/;
many more drivers/ to go)
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
more mutex debugging: check for held locks during memory freeing,
task exit, enable sysrq printouts, etc.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
RCU tasklist_lock and RCU signal handling: send signals RCU-read-locked
instead of tasklist_lock read-locked. This is a scalability improvement on
SMP and a preemption-latency improvement under PREEMPT_RCU.
Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: William Irwin <wli@holomorphy.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Ingo Molnar
Suresh Siddha
Eric W. Biederman
Oleg Nesterov
Adrian Bunk
Peter Williams
Alexey Dobriyan
Ulrich Drepper
Randy Dunlap
Nick Piggin
Satoru Takeuchi
Avi Kivity
Fenghua Yu
Rafael J. Wysocki
Thomas Gleixner
Mike Galbraith
Christoph Lameter
Linus Torvalds
Gautham R Shenoy
Andrew Morton
Dmitry Adamushko
Eric Dumazet
Jeremy Fitzhardinge
Christoph Lameter
Linus Torvalds
Con Kolivas
Zachary Amsden
Nick Piggin
Robert P. J. Day
Alexey Dobriyan
Nathan Lynch
Tim Chen
Mark Fasheh
Miguel Ojeda Sandonis
Chen, Kenneth W
Kirill Korotaev
Helge Deller
Chris Caputo
Peter Zijlstra
Nigel Cunningham
Borislav Petkov
Dave Jones
Greg Banks
Jay Lan
Akinobu Mita
Christoph Lameter
Heiko Carstens
Jim Houston
Chandra Seetharaman
Shailabh Nagar
Andreas Mohr
Andrew Morton
Steven Rostedt
Srivatsa Vaddagiri
Kirill Korotaev
Linus Torvalds
Andi Kleen
Paul Mackerras
David Quigley
Jack Steiner
KAMEZAWA Hiroyuki
Andreas Mohr
Martin Andersson
bibo mao
Anton Blanchard
Christoph Hellwig
Chuck Ebbert
Jason Baron
Arjan van de Ven
Randy.Dunlap