[tip:sched/core] sched/cputime: Use this_cpu_add() in task_group_account_field()

[tip:sched/core] sched/cputime: Use this_cpu_add() in task_group_account_field()

[tip-bot for Christoph Lameter]

Commit-ID:  a4f61cc03e443647211a5ae0ab8f8cda2e9e1043
Gitweb:     http://git.kernel.org/tip/a4f61cc03e443647211a5ae0ab8f8cda2e9e1043
Author:     Christoph Lameter <cl@gentwo.org>
AuthorDate: Wed, 7 Aug 2013 15:38:24 +0000
Committer:  Ingo Molnar <mingo@kernel.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@linux.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/00000140596dd165-338ff7f5-893b-4fec-b251-aaac5557239e-000000@email.amazonses.com
Signed-off-by: Ingo Molnar <mingo@kernel.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);
 }