From: Ken Chen <kenchen@google.com>
Date: Tue, 16 Dec 2008 06:02:01 +0000 (-0800)
Subject: sched, cpuacct: refactoring cpuusage_read / cpuusage_write
X-Git-Tag: v2.6.29-rc1~585^2~4
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=720f54988e17b33f3f477010b3a68ee872d20d5a;p=pandora-kernel.git

sched, cpuacct: refactoring cpuusage_read / cpuusage_write

Impact: micro-optimize the code on 64-bit architectures

In the thread regarding to 'export percpu cpuacct cgroup stats'
http://lkml.org/lkml/2008/12/7/13

akpm pointed out that current cpuacct code is inefficient.  This patch
refactoring the following:

* make cpu_rq locking only on 32-bit
* change iterator to each_present_cpu instead of each_possible_cpu to
  make it hotplug friendly.

It's a bit of code churn, but I was rewarded with 160 byte code size saving
on x86-64 arch and zero code size change on i386.

Signed-off-by: Ken Chen <kenchen@google.com>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

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