Commit-ID: 7a46c594bf7f1f2eeb1e12d4b857d5f581957a92
Gitweb: http://git.kernel.org/tip/7a46c594bf7f1f2eeb1e12d4b857d5f581957a92
Author: Li Zefan <lizf@xxxxxxxxxxxxxx>
AuthorDate: Thu, 12 Mar 2009 09:23:01 +0800
Commit: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Fri, 13 Mar 2009 04:54:58 +0100
cpuacct: reduce one NULL check in fast-path
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@xxxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Paul Menage <menage@xxxxxxxxxx>
Cc: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
Cc: Bharata B Rao <bharata@xxxxxxxxxxxxxxxxxx>
LKML-Reference: <49B863F5.2060400@xxxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/sched.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index 0a76d0b..61e6356 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -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 = {
--
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