Messages in this thread Patch in this message | | | Date | Fri, 29 Mar 2013 14:37:29 +0800 | From | Li Zefan <> | Subject | [PATCH v2 5/7] 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> --- kernel/sched/cpuacct.c | 6 +++++- kernel/sched/cpuacct.h | 2 +- 2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c index 72bd971..b2aaaba 100644 --- a/kernel/sched/cpuacct.c +++ b/kernel/sched/cpuacct.c @@ -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(); diff --git a/kernel/sched/cpuacct.h b/kernel/sched/cpuacct.h index bd0409b..45c1682 100644 --- a/kernel/sched/cpuacct.h +++ b/kernel/sched/cpuacct.h @@ -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); } -- 1.8.0.2
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