From: Christoph Lameter <cl@linux.com>
Date: Wed, 11 Sep 2013 21:21:30 +0000 (-0700)
Subject: vmstat: create separate function to fold per cpu diffs into local counters
X-Git-Tag: v3.12-rc1~52^2~231
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2bb921e526656556e68f99f5f15a4a1bf2691844;p=pandora-kernel.git

vmstat: create separate function to fold per cpu diffs into local counters

The main idea behind this patchset is to reduce the vmstat update overhead
by avoiding interrupt enable/disable and the use of per cpu atomics.

This patch (of 3):

It is better to have a separate folding function because
refresh_cpu_vm_stats() also does other things like expire pages in the
page allocator caches.

If we have a separate function then refresh_cpu_vm_stats() is only called
from the local cpu which allows additional optimizations.

The folding function is only called when a cpu is being downed and
therefore no other processor will be accessing the counters.  Also
simplifies synchronization.

[akpm@linux-foundation.org: fix UP build]
Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
CC: Tejun Heo <tj@kernel.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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