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: 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>
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 @@
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 *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);
}
