Commit Graph

25 Commits

Author SHA1 Message Date
Heiko Carstens 36cd3c9f92 mutex: have non-spinning mutexes on s390 by default
Impact: performance regression fix for s390

The adaptive spinning mutexes will not always do what one would expect on
virtualized architectures like s390. Especially the cpu_relax() loop in
mutex_spin_on_owner might hurt if the mutex holding cpu has been scheduled
away by the hypervisor.

We would end up in a cpu_relax() loop when there is no chance that the
state of the mutex changes until the target cpu has been scheduled again by
the hypervisor.

For that reason we should change the default behaviour to no-spin on s390.

We do have an instruction which allows to yield the current cpu in favour of
a different target cpu. Also we have an instruction which allows us to figure
out if the target cpu is physically backed.

However we need to do some performance tests until we can come up with
a solution that will do the right thing on s390.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
LKML-Reference: <20090409184834.7a0df7b2@osiris.boeblingen.de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-04-09 19:28:24 +02:00
Chris Mason ac6e60ee40 mutex: adaptive spinnning, performance tweaks
Spin more agressively. This is less fair but also markedly faster.

The numbers:

 * dbench 50 (higher is better):
  spin        1282MB/s
  v10         548MB/s
  v10 no wait 1868MB/s

 * 4k creates (numbers in files/second higher is better):
  spin        avg 200.60 median 193.20 std 19.71 high 305.93 low 186.82
  v10         avg 180.94 median 175.28 std 13.91 high 229.31 low 168.73
  v10 no wait avg 232.18 median 222.38 std 22.91 high 314.66 low 209.12

 * File stats (numbers in seconds, lower is better):
  spin        2.27s
  v10         5.1s
  v10 no wait 1.6s

( The source changes are smaller than they look, I just moved the
  need_resched checks in __mutex_lock_common after the cmpxchg. )

Signed-off-by: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-14 19:03:54 +01:00
Peter Zijlstra 0d66bf6d35 mutex: implement adaptive spinning
Change mutex contention behaviour such that it will sometimes busy wait on
acquisition - moving its behaviour closer to that of spinlocks.

This concept got ported to mainline from the -rt tree, where it was originally
implemented for rtmutexes by Steven Rostedt, based on work by Gregory Haskins.

Testing with Ingo's test-mutex application (http://lkml.org/lkml/2006/1/8/50)
gave a 345% boost for VFS scalability on my testbox:

 # ./test-mutex-shm V 16 10 | grep "^avg ops"
 avg ops/sec:               296604

 # ./test-mutex-shm V 16 10 | grep "^avg ops"
 avg ops/sec:               85870

The key criteria for the busy wait is that the lock owner has to be running on
a (different) cpu. The idea is that as long as the owner is running, there is a
fair chance it'll release the lock soon, and thus we'll be better off spinning
instead of blocking/scheduling.

Since regular mutexes (as opposed to rtmutexes) do not atomically track the
owner, we add the owner in a non-atomic fashion and deal with the races in
the slowpath.

Furthermore, to ease the testing of the performance impact of this new code,
there is means to disable this behaviour runtime (without having to reboot
the system), when scheduler debugging is enabled (CONFIG_SCHED_DEBUG=y),
by issuing the following command:

 # echo NO_OWNER_SPIN > /debug/sched_features

This command re-enables spinning again (this is also the default):

 # echo OWNER_SPIN > /debug/sched_features

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-14 18:09:02 +01:00
Peter Zijlstra 41719b0309 mutex: preemption fixes
The problem is that dropping the spinlock right before schedule is a voluntary
preemption point and can cause a schedule, right after which we schedule again.

Fix this inefficiency by keeping preemption disabled until we schedule, do this
by explicity disabling preemption and providing a schedule() variant that
assumes preemption is already disabled.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-14 18:09:00 +01:00
Peter Zijlstra 93d81d1aca mutex: small cleanup
Remove a local variable by combining an assingment and test in one.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-14 18:08:58 +01:00
Török Edwin 7918baa555 mutex: __used is needed for function referenced only from inline asm
Impact: fix build failure on llvm-gcc-4.2

According to the gcc manual, the 'used' attribute should be applied to
functions referenced only from inline assembly.
This fixes a build failure with llvm-gcc-4.2, which deleted
__mutex_lock_slowpath, __mutex_unlock_slowpath.

Signed-off-by: Török Edwin <edwintorok@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-24 10:00:28 +01:00
Peter Zijlstra c7e78cff6b lockstat: contend with points
We currently only provide points that have to wait on contention, also
lists the points we have to wait for.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-20 15:43:10 +02:00
Randy Dunlap 0e241ffd30 locking: fix mutex @key parameter kernel-doc notation
Fix @key parameter to mutex_init() and one of its callers.

Warning(linux-2.6.26-git11//drivers/base/class.c:210): No description found for parameter 'key'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-28 18:12:36 +02:00
Oleg Nesterov 6ad36762d7 __mutex_lock_common: use signal_pending_state()
Change __mutex_lock_common() to use signal_pending_state() for the sake of
the code re-use.

This adds 7 bytes to kernel/mutex.o, but afaics only because gcc isn't smart
enough.

(btw, uninlining of __mutex_lock_common() shrinks .text from 2722 to 1542,
 perhaps it is worth doing).

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-10 11:45:09 +02:00
Harvey Harrison 7ad5b3a505 kernel: remove fastcall in kernel/*
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.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>
2008-02-08 09:22:31 -08:00
Liam R. Howlett ad776537cc Add mutex_lock_killable
Similar to mutex_lock_interruptible, it can be interrupted by a fatal
signal only.

Signed-off-by: Liam R. Howlett <howlett@gmail.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
2007-12-06 17:37:59 -05:00
Peter Zijlstra e4564f79d4 lockdep: fixup mutex annotations
The fancy mutex_lock fastpath has too many indirections to track the caller
hence all contentions are perceived to come from mutex_lock().

Avoid this by explicitly not using the fastpath code (it was disabled already
anyway).

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2007-10-11 22:11:12 +02:00
Peter Zijlstra 96645678cd lockstat: measure lock bouncing
__acquire
        |
       lock _____
        |        \
        |    __contended
        |         |
        |        wait
        | _______/
        |/
        |
   __acquired
        |
   __release
        |
     unlock

We measure acquisition and contention bouncing.

This is done by recording a cpu stamp in each lock instance.

Contention bouncing requires the cpu stamp to be set on acquisition. Hence we
move __acquired into the generic path.

__acquired is then used to measure acquisition bouncing by comparing the
current cpu with the old stamp before replacing it.

__contended is used to measure contention bouncing (only useful for preemptable
locks)

[akpm@linux-foundation.org: cleanups]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
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>
2007-07-19 10:04:49 -07:00
Peter Zijlstra 4fe87745a6 lockstat: hook into spinlock_t, rwlock_t, rwsem and mutex
Call the new lockstat tracking functions from the various lock primitives.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-19 10:04:49 -07:00
Roman Zippel c9f4f06d31 wrap access to thread_info
Recently a few direct accesses to the thread_info in the task structure snuck
back, so this wraps them with the appropriate wrapper.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-09 12:30:56 -07:00
NeilBrown d63a5a74de [PATCH] lockdep: avoid lockdep warning in md
md_open takes ->reconfig_mutex which causes lockdep to complain.  This
(normally) doesn't have deadlock potential as the possible conflict is with a
reconfig_mutex in a different device.

I say "normally" because if a loop were created in the array->member hierarchy
a deadlock could happen.  However that causes bigger problems than a deadlock
and should be fixed independently.

So we flag the lock in md_open as a nested lock.  This requires defining
mutex_lock_interruptible_nested.

Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 08:28:39 -08:00
Ingo Molnar ef5d4707b9 [PATCH] lockdep: prove mutex locking correctness
Use the lock validator framework to prove mutex 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>
2006-07-03 15:27:04 -07:00
Ingo Molnar 9cebb55268 [PATCH] lockdep: mutex section binutils workaround
Work around weird section nesting build bug causing smp-alternatives failures
under certain circumstances.

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>
2006-07-03 15:27:01 -07:00
Ingo Molnar 9a11b49a80 [PATCH] lockdep: better lock debugging
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>
2006-07-03 15:27:01 -07:00
Ingo Molnar 9e7f4d451e [PATCH] lockdep: rename DEBUG_WARN_ON()
Rename DEBUG_WARN_ON() to the less generic DEBUG_LOCKS_WARN_ON() name, so that
it's clear that this is a lock-debugging internal mechanism.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-07-03 15:27:01 -07:00
Ingo Molnar 1fb00c6cbd [PATCH] work around ppc64 bootup bug by making mutex-debugging save/restore irqs
It seems ppc64 wants to lock mutexes in early bootup code, with interrupts
disabled, and they expect interrupts to stay disabled, else they crash.

Work around this bug by making mutex debugging variants save/restore irq
flags.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-26 09:58:16 -07:00
Ingo Molnar 02706647a4 [PATCH] mutex: trivial whitespace cleanups
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-10 14:27:59 -08:00
Ingo Molnar c544bdb199 [PATCH] mark mutex_lock*() as might_sleep()
Mark mutex_lock() and mutex_lock_interruptible() as might_sleep()
functions.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-10 13:20:47 -08:00
Ingo Molnar 73165b88ff [PATCH] fix i386 mutex fastpath on FRAME_POINTER && !DEBUG_MUTEXES
Call the mutex slowpath more conservatively - e.g.  FRAME_POINTERS can
change the calling convention, in which case a direct branch to the
slowpath becomes illegal.  Bug found by Hugh Dickins.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-10 13:20:47 -08:00
Ingo Molnar 6053ee3b32 [PATCH] mutex subsystem, core
mutex implementation, core files: just the basic subsystem, no users of it.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
2006-01-09 15:59:19 -08:00