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cpuacct: reduce one NULL check in fast-path

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Impact: micro-optimization

In cpuacct_charge(), task_ca() will never return NULL, so change
for(...) to do { } while(...) to save one NULL check.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Menage <menage@google.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Bharata B Rao <bharata@linux.vnet.ibm.com>
LKML-Reference: <49B863F5.2060400@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Li Zefan 2009-03-12 09:23:01 +08:00 committed by Ingo Molnar
parent 65a37b29a8
commit 7a46c594bf
1 changed files with 3 additions and 2 deletions
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5
kernel/sched.c
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@ -9599,10 +9599,11 @@ static void cpuacct_charge(struct task_struct *tsk, u64 cputime)
cpu = task_cpu(tsk);
ca = task_ca(tsk);
for (; ca; ca = ca->parent) {
do {
u64 *cpuusage = per_cpu_ptr(ca->cpuusage, cpu);
*cpuusage += cputime;
}
ca = ca->parent;
} while (ca);
}
struct cgroup_subsys cpuacct_subsys = {