If we want to stop the tick further idle, we need to be
able to account the cputime without using the tick.
Virtual based cputime accounting solves that problem by
hooking into kernel/user boundaries.
However implementing CONFIG_VIRT_CPU_ACCOUNTING require
low level hooks and involves more overhead. But we already
have a generic context tracking subsystem that is required
for RCU needs by archs which plan to shut down the tick
outside idle.
This patch implements a generic virtual based cputime
accounting that relies on these generic kernel/user hooks.
There are some upsides of doing this:
- This requires no arch code to implement CONFIG_VIRT_CPU_ACCOUNTING
if context tracking is already built (already necessary for RCU in full
tickless mode).
- We can rely on the generic context tracking subsystem to dynamically
(de)activate the hooks, so that we can switch anytime between virtual
and tick based accounting. This way we don't have the overhead
of the virtual accounting when the tick is running periodically.
And one downside:
- There is probably more overhead than a native virtual based cputime
accounting. But this relies on hooks that are already set anyway.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Reformat lppaca.h to match Linux coding standards.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Remove all the iseries specific fields in the lppaca.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
We have a union containing fields from the old iseries hypervisor
that has been reused for the cede latency hint. Since we no
longer support iseries, remove the union completely.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Future releases of fimrware will enforce a requirement that DTL buffers
do not cross a 4k boundary. Commit
127493d5dc satisfies this requirement for
CONFIG_VIRT_CPU_ACCOUNTING=y kernels, but if !CONFIG_VIRT_CPU_ACCOUNTING
&& CONFIG_DTL=y, the current code will fail at dtl registration time.
Fix this by making the kmem cache from
127493d5dc visible outside of setup.c and
using the same cache in both dtl.c and setup.c. This requires a bit of
reorganization to ensure ordering of the kmem cache and buffer
allocations.
Note: Since firmware now limits the size of the buffer, I made
dtl_buf_entries read-only in debugfs.
Tested with upcoming firmware with the 4 combinations of
CONFIG_VIRT_CPU_ACCOUNTING and CONFIG_DTL.
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Anton Blanchard <anton@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
The combination of commit
8154c5d22d and
93c22703ef
Broke boot on iSeries.
The problem is that iSeries very early boot code, which generates
the device-tree and runs before our normal early initializations
does need access the lppaca's very early, before the PACA array is
initialized, and in fact even before the boot PACA has been
initialized (it contains all 0's at this stage).
However, the first patch above makes that code use the new
llpaca_of(cpu) accessor, which itself is changed by the second patch to
use the PACA array.
We fix that by reverting iSeries to directly dereferencing the array. In
addition, we fix all iterators in the iSeries code to always skip CPU
whose number is above 63 which is the maximum size of that array and
the maximum number of supported CPUs on these machines.
Additionally, we make sure the boot_paca is properly initialized
in our early startup code.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This patch sets a timer during boot that will periodically poll the
associativity change counters in the VPA. When a change in
associativity is detected, it retrieves the new associativity domain
information via the H_HOME_NODE_ASSOCIATIVITY hcall and updates the
NUMA node maps and sysfs entries accordingly. Note that since the
ibm,associativity device tree property does not exist on configurations
with both NUMA and SPLPAR enabled, no device tree updates are necessary.
Signed-off-by: Jesse Larrew <jlarrew@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Since the cpu accounting code uses the hypervisor dispatch trace log
now when CONFIG_VIRT_CPU_ACCOUNTING = y, the previous commit disabled
access to it via files in the /sys/kernel/debug/powerpc/dtl/ directory
in that case. This restores those files.
To do this, we now have a hook that the cpu accounting code will call
as it processes each entry from the hypervisor dispatch trace log.
The code in dtl.c now uses that to fill up its ring buffer, rather
than having the hypervisor fill the ring buffer directly.
This also fixes dtl_file_read() to handle overflow conditions a bit
better and adds a spinlock to ensure that race conditions (multiple
processes opening or reading the file concurrently) are handled
correctly.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Currently, when CONFIG_VIRT_CPU_ACCOUNTING is enabled, we use the
PURR register for measuring the user and system time used by
processes, as well as other related times such as hardirq and
softirq times. This turns out to be quite confusing for users
because it means that a program will often be measured as taking
less time when run on a multi-threaded processor (SMT2 or SMT4 mode)
than it does when run on a single-threaded processor (ST mode), even
though the program takes longer to finish. The discrepancy is
accounted for as stolen time, which is also confusing, particularly
when there are no other partitions running.
This changes the accounting to use the timebase instead, meaning that
the reported user and system times are the actual number of real-time
seconds that the program was executing on the processor thread,
regardless of which SMT mode the processor is in. Thus a program will
generally show greater user and system times when run on a
multi-threaded processor than on a single-threaded processor.
On pSeries systems on POWER5 or later processors, we measure the
stolen time (time when this partition wasn't running) using the
hypervisor dispatch trace log. We check for new entries in the
log on every entry from user mode and on every transition from
kernel process context to soft or hard IRQ context (i.e. when
account_system_vtime() gets called). So that we can correctly
distinguish time stolen from user time and time stolen from system
time, without having to check the log on every exit to user mode,
we store separate timestamps for exit to user mode and entry from
user mode.
On systems that have a SPURR (POWER6 and POWER7), we read the SPURR
in account_system_vtime() (as before), and then apportion the SPURR
ticks since the last time we read it between scaled user time and
scaled system time according to the relative proportions of user
time and system time over the same interval. This avoids having to
read the SPURR on every kernel entry and exit. On systems that have
PURR but not SPURR (i.e., POWER5), we do the same using the PURR
rather than the SPURR.
This disables the DTL user interface in /sys/debug/kernel/powerpc/dtl
for now since it conflicts with the use of the dispatch trace log
by the time accounting code.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This arranges for the lppaca structs for most cpus to be dynamically
allocated in the same manner as the paca structs. If we don't include
support for legacy iSeries, only the first lppaca is statically
allocated; the rest are dynamically allocated. If we include legacy
iSeries support, then we statically allocate the first 64 lppaca
structs, since the iSeries hypervisor requires that the lppaca
structs be present in the data section of the kernel image, but
legacy iSeries supports at most 64 cpus.
With CONFIG_NR_CPUS, the kernel image size for a typical pSeries config
went from:
text data bss dec hex filename
9524478 4734564 8469944 22728986 15ad11a ../test-1024/vmlinux
to:
text data bss dec hex filename
9524482 3751508 8469944 21745934 14bd10e ../test-1024/vmlinux
a reduction of 983052 bytes overall.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Currently we have the lppaca structs as a simple array of NR_CPUS
entries, taking up space in the data section of the kernel image.
In future we would like to allocate them dynamically, so this
abstracts out the accesses to the array, making it easier to
change how we locate the lppaca for a given cpu in future.
Specifically, lppaca[cpu] changes to lppaca_of(cpu).
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This patch provides an extended_cede_processor() helper function
which takes the cede latency hint as an argument. This hint is to be passed
on to the hypervisor to cede to the corresponding state on platforms
which support it.
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This is a random collection of added ifdef's around portions of
code that only mak sense on server processors. Using either
CONFIG_PPC_STD_MMU_64 or CONFIG_PPC_BOOK3S as seems appropriate.
This is meant to make the future merging of Book3E 64-bit support
easier.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
PHYP tells us how often a shared processor dispatch changed physical cpus.
This can highlight performance problems caused by the hypervisor.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
PAPR v2.3 defines fields in the virtual processor area for a dispatch
trace log (DLT). Since we'd like to use the DLT, add the necessary
fields to struct lppaca.
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
The page_ins member ends at byte 0x3, not 0x4. Also, fix up the
alignment.
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
A new field has been added to the VPA as a method for the client OS to
communicate to firmware the number of page-ins it is performing when
running collaborative memory overcommit. The hypervisor will use this
information to better determine if a partition is experiencing memory
pressure and needs more memory allocated to it.
Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
from include/asm-powerpc. This is the result of a
mkdir arch/powerpc/include/asm
git mv include/asm-powerpc/* arch/powerpc/include/asm
Followed by a few documentation/comment fixups and a couple of places
where <asm-powepc/...> was being used explicitly. Of the latter only
one was outside the arch code and it is a driver only built for powerpc.
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Frederic Weisbecker
Anton Blanchard
Stephen Rothwell
Nishanth Aravamudan
Lucas De Marchi
Benjamin Herrenschmidt
Jesse Larrew
Paul Mackerras
Gautham R Shenoy
Jeremy Kerr
Brian King