Commit-ID: 543bc0e76e6bb84300eaf9833edc5a481f788678
Gitweb: http://git.kernel.org/tip/543bc0e76e6bb84300eaf9833edc5a481f788678
Author: Li Zefan <lizefan@xxxxxxxxxx>
AuthorDate: Fri, 29 Mar 2013 14:37:29 +0800
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 10 Apr 2013 13:54:18 +0200
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@xxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/515536A9.5000700@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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);
}
--
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