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Commit 543bc0e7 authored by Li Zefan's avatar Li Zefan Committed by Ingo Molnar
Browse files

sched/cpuacct: Remove redundant NULL checks in cpuacct_charge() 



This is a micro optimization for the hot path.

- We don't need to check if @ca is NULL in parent_ca().
- We don't need to check if @ca is NULL in the beginning of the for loop.

Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/515536A9.5000700@huawei.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 1966aaf7

kernel/sched/cpuacct.c

+5 −1
Original line number Diff line number Diff line
@@ -210,9 +210,13 @@ void cpuacct_charge(struct task_struct *tsk, u64 cputime) 


	ca = task_ca(tsk);



	for (; ca; ca = parent_ca(ca)) {

	while (true) {

		u64 *cpuusage = per_cpu_ptr(ca->cpuusage, cpu);

		*cpuusage += cputime;



		ca = parent_ca(ca);

		if (!ca)

			break;

	}



	rcu_read_unlock();

kernel/sched/cpuacct.h

+1 −1
Original line number Diff line number Diff line
@@ -36,7 +36,7 @@ static inline struct cpuacct *task_ca(struct task_struct *tsk) 


static inline struct cpuacct *parent_ca(struct cpuacct *ca)

{

	if (!ca || !ca->css.cgroup->parent)

	if (!ca->css.cgroup->parent)

		return NULL;

	return cgroup_ca(ca->css.cgroup->parent);

}