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

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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: Li Zefan <lizefan@huawei.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/515536A9.5000700@huawei.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Li Zefan 2013-03-29 14:37:29 +08:00 committed by Ingo Molnar
parent 1966aaf7d5
commit 543bc0e76e
2 changed files with 6 additions and 2 deletions
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6
kernel/sched/cpuacct.c
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@ -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();

2
kernel/sched/cpuacct.h
View file

@ -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);
}