linux-toradex.git/mm/vmstat.c, branch v2.6.38-rc8 Linux kernel for Apalis and Colibri modules thp: transparent hugepage vmstat 2011-01-14T01:32:43+00:00 Andrea Arcangeli aarcange@redhat.com 2011-01-13T23:46:58+00:00 79134171df238171daa4c024a42b77b401ccb00b Add hugepage stat information to /proc/vmstat and /proc/meminfo. Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Acked-by: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
Add hugepage stat information to /proc/vmstat and /proc/meminfo.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm: vmstat: use a single setter function and callback for adjusting percpu thresholds 2011-01-14T01:32:31+00:00 Mel Gorman mel@csn.ul.ie 2011-01-13T23:45:43+00:00 b44129b30652c8771db2265939bb8b463724043d reduce_pgdat_percpu_threshold() and restore_pgdat_percpu_threshold() exist to adjust the per-cpu vmstat thresholds while kswapd is awake to avoid errors due to counter drift. The functions duplicate some code so this patch replaces them with a single set_pgdat_percpu_threshold() that takes a callback function to calculate the desired threshold as a parameter. [akpm@linux-foundation.org: readability tweak] [kosaki.motohiro@jp.fujitsu.com: set_pgdat_percpu_threshold(): don't use for_each_online_cpu] Signed-off-by: Mel Gorman <mel@csn.ul.ie> Reviewed-by: Christoph Lameter <cl@linux.com> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
reduce_pgdat_percpu_threshold() and restore_pgdat_percpu_threshold() exist
to adjust the per-cpu vmstat thresholds while kswapd is awake to avoid
errors due to counter drift.  The functions duplicate some code so this
patch replaces them with a single set_pgdat_percpu_threshold() that takes
a callback function to calculate the desired threshold as a parameter.

[akpm@linux-foundation.org: readability tweak]
[kosaki.motohiro@jp.fujitsu.com: set_pgdat_percpu_threshold(): don't use for_each_online_cpu]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Christoph Lameter <cl@linux.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm: page allocator: adjust the per-cpu counter threshold when memory is low 2011-01-14T01:32:31+00:00 Mel Gorman mel@csn.ul.ie 2011-01-13T23:45:41+00:00 88f5acf88ae6a9778f6d25d0d5d7ec2d57764a97 Commit aa45484 ("calculate a better estimate of NR_FREE_PAGES when memory is low") noted that watermarks were based on the vmstat NR_FREE_PAGES. To avoid synchronization overhead, these counters are maintained on a per-cpu basis and drained both periodically and when a threshold is above a threshold. On large CPU systems, the difference between the estimate and real value of NR_FREE_PAGES can be very high. The system can get into a case where pages are allocated far below the min watermark potentially causing livelock issues. The commit solved the problem by taking a better reading of NR_FREE_PAGES when memory was low. Unfortately, as reported by Shaohua Li this accurate reading can consume a large amount of CPU time on systems with many sockets due to cache line bouncing. This patch takes a different approach. For large machines where counter drift might be unsafe and while kswapd is awake, the per-cpu thresholds for the target pgdat are reduced to limit the level of drift to what should be a safe level. This incurs a performance penalty in heavy memory pressure by a factor that depends on the workload and the machine but the machine should function correctly without accidentally exhausting all memory on a node. There is an additional cost when kswapd wakes and sleeps but the event is not expected to be frequent - in Shaohua's test case, there was one recorded sleep and wake event at least. To ensure that kswapd wakes up, a safe version of zone_watermark_ok() is introduced that takes a more accurate reading of NR_FREE_PAGES when called from wakeup_kswapd, when deciding whether it is really safe to go back to sleep in sleeping_prematurely() and when deciding if a zone is really balanced or not in balance_pgdat(). We are still using an expensive function but limiting how often it is called. When the test case is reproduced, the time spent in the watermark functions is reduced. The following report is on the percentage of time spent cumulatively spent in the functions zone_nr_free_pages(), zone_watermark_ok(), __zone_watermark_ok(), zone_watermark_ok_safe(), zone_page_state_snapshot(), zone_page_state(). vanilla 11.6615% disable-threshold 0.2584% David said: : We had to pull aa454840 "mm: page allocator: calculate a better estimate : of NR_FREE_PAGES when memory is low and kswapd is awake" from 2.6.36 : internally because tests showed that it would cause the machine to stall : as the result of heavy kswapd activity. I merged it back with this fix as : it is pending in the -mm tree and it solves the issue we were seeing, so I : definitely think this should be pushed to -stable (and I would seriously : consider it for 2.6.37 inclusion even at this late date). Signed-off-by: Mel Gorman <mel@csn.ul.ie> Reported-by: Shaohua Li <shaohua.li@intel.com> Reviewed-by: Christoph Lameter <cl@linux.com> Tested-by: Nicolas Bareil <nico@chdir.org> Cc: David Rientjes <rientjes@google.com> Cc: Kyle McMartin <kyle@mcmartin.ca> Cc: <stable@kernel.org> [2.6.37.1, 2.6.36.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
Commit aa45484 ("calculate a better estimate of NR_FREE_PAGES when memory
is low") noted that watermarks were based on the vmstat NR_FREE_PAGES.  To
avoid synchronization overhead, these counters are maintained on a per-cpu
basis and drained both periodically and when a threshold is above a
threshold.  On large CPU systems, the difference between the estimate and
real value of NR_FREE_PAGES can be very high.  The system can get into a
case where pages are allocated far below the min watermark potentially
causing livelock issues.  The commit solved the problem by taking a better
reading of NR_FREE_PAGES when memory was low.

Unfortately, as reported by Shaohua Li this accurate reading can consume a
large amount of CPU time on systems with many sockets due to cache line
bouncing.  This patch takes a different approach.  For large machines
where counter drift might be unsafe and while kswapd is awake, the per-cpu
thresholds for the target pgdat are reduced to limit the level of drift to
what should be a safe level.  This incurs a performance penalty in heavy
memory pressure by a factor that depends on the workload and the machine
but the machine should function correctly without accidentally exhausting
all memory on a node.  There is an additional cost when kswapd wakes and
sleeps but the event is not expected to be frequent - in Shaohua's test
case, there was one recorded sleep and wake event at least.

To ensure that kswapd wakes up, a safe version of zone_watermark_ok() is
introduced that takes a more accurate reading of NR_FREE_PAGES when called
from wakeup_kswapd, when deciding whether it is really safe to go back to
sleep in sleeping_prematurely() and when deciding if a zone is really
balanced or not in balance_pgdat().  We are still using an expensive
function but limiting how often it is called.

When the test case is reproduced, the time spent in the watermark
functions is reduced.  The following report is on the percentage of time
spent cumulatively spent in the functions zone_nr_free_pages(),
zone_watermark_ok(), __zone_watermark_ok(), zone_watermark_ok_safe(),
zone_page_state_snapshot(), zone_page_state().

vanilla                      11.6615%
disable-threshold            0.2584%

David said:

: We had to pull aa454840 "mm: page allocator: calculate a better estimate
: of NR_FREE_PAGES when memory is low and kswapd is awake" from 2.6.36
: internally because tests showed that it would cause the machine to stall
: as the result of heavy kswapd activity.  I merged it back with this fix as
: it is pending in the -mm tree and it solves the issue we were seeing, so I
: definitely think this should be pushed to -stable (and I would seriously
: consider it for 2.6.37 inclusion even at this late date).

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reported-by: Shaohua Li <shaohua.li@intel.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Tested-by: Nicolas Bareil <nico@chdir.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: <stable@kernel.org>		[2.6.37.1, 2.6.36.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge branch 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2011-01-08T01:02:58+00:00 Linus Torvalds torvalds@linux-foundation.org 2011-01-08T01:02:58+00:00 72eb6a791459c87a0340318840bb3bd9252b627b * 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (30 commits) gameport: use this_cpu_read instead of lookup x86: udelay: Use this_cpu_read to avoid address calculation x86: Use this_cpu_inc_return for nmi counter x86: Replace uses of current_cpu_data with this_cpu ops x86: Use this_cpu_ops to optimize code vmstat: User per cpu atomics to avoid interrupt disable / enable irq_work: Use per cpu atomics instead of regular atomics cpuops: Use cmpxchg for xchg to avoid lock semantics x86: this_cpu_cmpxchg and this_cpu_xchg operations percpu: Generic this_cpu_cmpxchg() and this_cpu_xchg support percpu,x86: relocate this_cpu_add_return() and friends connector: Use this_cpu operations xen: Use this_cpu_inc_return taskstats: Use this_cpu_ops random: Use this_cpu_inc_return fs: Use this_cpu_inc_return in buffer.c highmem: Use this_cpu_xx_return() operations vmstat: Use this_cpu_inc_return for vm statistics x86: Support for this_cpu_add, sub, dec, inc_return percpu: Generic support for this_cpu_add, sub, dec, inc_return ... Fixed up conflicts: in arch/x86/kernel/{apic/nmi.c, apic/x2apic_uv_x.c, process.c} as per Tejun. 
* 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (30 commits)
  gameport: use this_cpu_read instead of lookup
  x86: udelay: Use this_cpu_read to avoid address calculation
  x86: Use this_cpu_inc_return for nmi counter
  x86: Replace uses of current_cpu_data with this_cpu ops
  x86: Use this_cpu_ops to optimize code
  vmstat: User per cpu atomics to avoid interrupt disable / enable
  irq_work: Use per cpu atomics instead of regular atomics
  cpuops: Use cmpxchg for xchg to avoid lock semantics
  x86: this_cpu_cmpxchg and this_cpu_xchg operations
  percpu: Generic this_cpu_cmpxchg() and this_cpu_xchg support
  percpu,x86: relocate this_cpu_add_return() and friends
  connector: Use this_cpu operations
  xen: Use this_cpu_inc_return
  taskstats: Use this_cpu_ops
  random: Use this_cpu_inc_return
  fs: Use this_cpu_inc_return in buffer.c
  highmem: Use this_cpu_xx_return() operations
  vmstat: Use this_cpu_inc_return for vm statistics
  x86: Support for this_cpu_add, sub, dec, inc_return
  percpu: Generic support for this_cpu_add, sub, dec, inc_return
  ...

Fixed up conflicts: in arch/x86/kernel/{apic/nmi.c, apic/x2apic_uv_x.c, process.c}
as per Tejun.
Merge branch 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2011-01-08T00:58:04+00:00 Linus Torvalds torvalds@linux-foundation.org 2011-01-08T00:58:04+00:00 23d69b09b78c4876e134f104a3814c30747c53f1 * 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: (33 commits) usb: don't use flush_scheduled_work() speedtch: don't abuse struct delayed_work media/video: don't use flush_scheduled_work() media/video: explicitly flush request_module work ioc4: use static work_struct for ioc4_load_modules() init: don't call flush_scheduled_work() from do_initcalls() s390: don't use flush_scheduled_work() rtc: don't use flush_scheduled_work() mmc: update workqueue usages mfd: update workqueue usages dvb: don't use flush_scheduled_work() leds-wm8350: don't use flush_scheduled_work() mISDN: don't use flush_scheduled_work() macintosh/ams: don't use flush_scheduled_work() vmwgfx: don't use flush_scheduled_work() tpm: don't use flush_scheduled_work() sonypi: don't use flush_scheduled_work() hvsi: don't use flush_scheduled_work() xen: don't use flush_scheduled_work() gdrom: don't use flush_scheduled_work() ... Fixed up trivial conflict in drivers/media/video/bt8xx/bttv-input.c as per Tejun. 
* 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: (33 commits)
  usb: don't use flush_scheduled_work()
  speedtch: don't abuse struct delayed_work
  media/video: don't use flush_scheduled_work()
  media/video: explicitly flush request_module work
  ioc4: use static work_struct for ioc4_load_modules()
  init: don't call flush_scheduled_work() from do_initcalls()
  s390: don't use flush_scheduled_work()
  rtc: don't use flush_scheduled_work()
  mmc: update workqueue usages
  mfd: update workqueue usages
  dvb: don't use flush_scheduled_work()
  leds-wm8350: don't use flush_scheduled_work()
  mISDN: don't use flush_scheduled_work()
  macintosh/ams: don't use flush_scheduled_work()
  vmwgfx: don't use flush_scheduled_work()
  tpm: don't use flush_scheduled_work()
  sonypi: don't use flush_scheduled_work()
  hvsi: don't use flush_scheduled_work()
  xen: don't use flush_scheduled_work()
  gdrom: don't use flush_scheduled_work()
  ...

Fixed up trivial conflict in drivers/media/video/bt8xx/bttv-input.c
as per Tejun.
vmstat: User per cpu atomics to avoid interrupt disable / enable 2010-12-18T14:54:49+00:00 Christoph Lameter cl@linux.com 2010-12-14T16:28:46+00:00 7c83912062c801738d7d19acaf8f7fec25ea663c Currently the operations to increment vm counters must disable interrupts in order to not mess up their housekeeping of counters. So use this_cpu_cmpxchg() to avoid the overhead. Since we can no longer count on preremption being disabled we still have some minor issues. The fetching of the counter thresholds is racy. A threshold from another cpu may be applied if we happen to be rescheduled on another cpu. However, the following vmstat operation will then bring the counter again under the threshold limit. The operations for __xxx_zone_state are not changed since the caller has taken care of the synchronization needs (and therefore the cycle count is even less than the optimized version for the irq disable case provided here). The optimization using this_cpu_cmpxchg will only be used if the arch supports efficient this_cpu_ops (must have CONFIG_CMPXCHG_LOCAL set!) The use of this_cpu_cmpxchg reduces the cycle count for the counter operations by %80 (inc_zone_page_state goes from 170 cycles to 32). Signed-off-by: Christoph Lameter <cl@linux.com> 
Currently the operations to increment vm counters must disable interrupts
in order to not mess up their housekeeping of counters.

So use this_cpu_cmpxchg() to avoid the overhead. Since we can no longer
count on preremption being disabled we still have some minor issues.
The fetching of the counter thresholds is racy.
A threshold from another cpu may be applied if we happen to be
rescheduled on another cpu.  However, the following vmstat operation
will then bring the counter again under the threshold limit.

The operations for __xxx_zone_state are not changed since the caller
has taken care of the synchronization needs (and therefore the cycle
count is even less than the optimized version for the irq disable case
provided here).

The optimization using this_cpu_cmpxchg will only be used if the arch
supports efficient this_cpu_ops (must have CONFIG_CMPXCHG_LOCAL set!)

The use of this_cpu_cmpxchg reduces the cycle count for the counter
operations by %80 (inc_zone_page_state goes from 170 cycles to 32).

Signed-off-by: Christoph Lameter <cl@linux.com>
vmstat: Use this_cpu_inc_return for vm statistics 2010-12-17T14:18:04+00:00 Christoph Lameter cl@linux.com 2010-12-06T17:40:02+00:00 908ee0f122bf2a67414854af5b90c6621d186a71 this_cpu_inc_return() saves us a memory access there. Code size does not change. V1->V2: - Fixed the location of the __per_cpu pointer attributes - Sparse checked V2->V3: - Move fixes to __percpu attribute usage to earlier patch Reviewed-by: Pekka Enberg <penberg@kernel.org> Acked-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Christoph Lameter <cl@linux.com> Signed-off-by: Tejun Heo <tj@kernel.org> 
this_cpu_inc_return() saves us a memory access there. Code
size does not change.

V1->V2:
	- Fixed the location of the __per_cpu pointer attributes
	- Sparse checked
V2->V3:
	- Move fixes to __percpu attribute usage to earlier patch

Reviewed-by: Pekka Enberg <penberg@kernel.org>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
vmstat: Optimize zone counter modifications through the use of this cpu operations 2010-12-17T14:07:18+00:00 Christoph Lameter cl@linux.com 2010-12-06T17:16:20+00:00 12938a9220a38d555e38dc9b40021e664b99a1f1 this cpu operations can be used to slightly optimize the function. The changes will avoid some address calculations and replace them with the use of the percpu segment register. If one would have this_cpu_inc_return and this_cpu_dec_return then it would be possible to optimize inc_zone_page_state and dec_zone_page_state even more. V1->V2: - Fix __dec_zone_state overflow handling - Use s8 variables for temporary storage. V2->V3: - Put __percpu annotations in correct places. Reviewed-by: Pekka Enberg <penberg@kernel.org> Acked-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Christoph Lameter <cl@linux.com> Signed-off-by: Tejun Heo <tj@kernel.org> 
this cpu operations can be used to slightly optimize the function. The
changes will avoid some address calculations and replace them with the
use of the percpu segment register.

If one would have this_cpu_inc_return and this_cpu_dec_return then it
would be possible to optimize inc_zone_page_state and
dec_zone_page_state even more.

V1->V2:
	- Fix __dec_zone_state overflow handling
	- Use s8 variables for temporary storage.

V2->V3:
	- Put __percpu annotations in correct places.

Reviewed-by: Pekka Enberg <penberg@kernel.org>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
workqueue: convert cancel_rearming_delayed_work[queue]() users to cancel_delayed_work_sync() 2010-12-15T09:56:11+00:00 Tejun Heo tj@kernel.org 2010-12-14T15:21:17+00:00 afe2c511fb2d75f1515081ff1be15bd79cfe722d cancel_rearming_delayed_work[queue]() has been superceded by cancel_delayed_work_sync() quite some time ago. Convert all the in-kernel users. The conversions are completely equivalent and trivial. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: "David S. Miller" <davem@davemloft.net> Acked-by: Greg Kroah-Hartman <gregkh@suse.de> Acked-by: Evgeniy Polyakov <zbr@ioremap.net> Cc: Jeff Garzik <jgarzik@pobox.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Mauro Carvalho Chehab <mchehab@infradead.org> Cc: netdev@vger.kernel.org Cc: Anton Vorontsov <cbou@mail.ru> Cc: David Woodhouse <dwmw2@infradead.org> Cc: "J. Bruce Fields" <bfields@fieldses.org> Cc: Neil Brown <neilb@suse.de> Cc: Alex Elder <aelder@sgi.com> Cc: xfs-masters@oss.sgi.com Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Pekka Enberg <penberg@cs.helsinki.fi> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: netfilter-devel@vger.kernel.org Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Cc: linux-nfs@vger.kernel.org 
cancel_rearming_delayed_work[queue]() has been superceded by
cancel_delayed_work_sync() quite some time ago.  Convert all the
in-kernel users.  The conversions are completely equivalent and
trivial.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: "David S. Miller" <davem@davemloft.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Jeff Garzik <jgarzik@pobox.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
Cc: netdev@vger.kernel.org
Cc: Anton Vorontsov <cbou@mail.ru>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Neil Brown <neilb@suse.de>
Cc: Alex Elder <aelder@sgi.com>
Cc: xfs-masters@oss.sgi.com
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: netfilter-devel@vger.kernel.org
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: linux-nfs@vger.kernel.org
vmstat: fix dirty threshold ordering 2010-12-02T22:51:14+00:00 Wu Fengguang fengguang.wu@intel.com 2010-12-02T22:31:13+00:00 e172662d113ceb22db727a979bb35b9c02f703b5 The nr_dirty_[background_]threshold fields are misplaced before the numa_* fields, and users will read strange values. This is the right order. Before patch, nr_dirty_background_threshold will read as 0 (the value from numa_miss). numa_hit 128501 numa_miss 0 numa_foreign 0 numa_interleave 7388 numa_local 128501 numa_other 0 nr_dirty_threshold 144291 nr_dirty_background_threshold 72145 Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Cc: Michael Rubin <mrubin@google.com> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
The nr_dirty_[background_]threshold fields are misplaced before the
numa_* fields, and users will read strange values.

This is the right order.  Before patch, nr_dirty_background_threshold
will read as 0 (the value from numa_miss).

	numa_hit 128501
	numa_miss 0
	numa_foreign 0
	numa_interleave 7388
	numa_local 128501
	numa_other 0
	nr_dirty_threshold 144291
	nr_dirty_background_threshold 72145

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Michael Rubin <mrubin@google.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>