linux-kernel - [tip:sched/core] sched/cputime: Use this_cpu_add() in task_group_account

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Date:	Fri, 16 Aug 2013 11:46:35 -0700
From:	tip-bot for Christoph Lameter <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	peterz@...radead.org, cl@...two.org, cl@...ux.com,
	tglx@...utronix.de
Subject: [tip:sched/core] sched/cputime: Use this_cpu_add()
  in task_group_account_field()

Commit-ID:  a4f61cc03e443647211a5ae0ab8f8cda2e9e1043
Gitweb:     http://git.kernel.org/tip/a4f61cc03e443647211a5ae0ab8f8cda2e9e1043
Author:     Christoph Lameter <cl@...two.org>
AuthorDate: Wed, 7 Aug 2013 15:38:24 +0000
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 16 Aug 2013 17:44:29 +0200

sched/cputime: Use this_cpu_add() in task_group_account_field()

Use of a this_cpu() operation reduces the number of instructions used
for accounting (account_user_time()) and frees up some registers. This is in
the scheduler tick hotpath.

Signed-off-by: Christoph Lameter <cl@...ux.com>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/00000140596dd165-338ff7f5-893b-4fec-b251-aaac5557239e-000000@email.amazonses.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/cputime.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index a7959e0..e89ccef 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -121,7 +121,7 @@ static inline void task_group_account_field(struct task_struct *p, int index,
 	 * is the only cgroup, then nothing else should be necessary.
 	 *
 	 */
-	__get_cpu_var(kernel_cpustat).cpustat[index] += tmp;
+	__this_cpu_add(kernel_cpustat.cpustat[index], tmp);
 
 	cpuacct_account_field(p, index, tmp);
 }
--
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