From: Jason Low Date: Wed, 14 Oct 2015 19:07:53 +0000 (-0700) Subject: posix_cpu_timer: Optimize fastpath_timer_check() X-Git-Tag: firefly_0821_release~176^2~839^2~7 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=7c177d994eb9637302b79e80d331f48dfbe26368;p=firefly-linux-kernel-4.4.55.git posix_cpu_timer: Optimize fastpath_timer_check() In fastpath_timer_check(), the task_cputime() function is always called to compute the utime and stime values. However, this is not necessary if there are no per-thread timers to check for. This patch modifies the code such that we compute the task_cputime values only when there are per-thread timers set. Signed-off-by: Jason Low Reviewed-by: Oleg Nesterov Reviewed-by: Frederic Weisbecker Reviewed-by: Davidlohr Bueso Reviewed-by: George Spelvin Cc: Paul E. McKenney Cc: Steven Rostedt Cc: hideaki.kimura@hpe.com Cc: terry.rudd@hpe.com Cc: scott.norton@hpe.com Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1444849677-29330-2-git-send-email-jason.low2@hp.com Signed-off-by: Thomas Gleixner --- diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 892e3dae0aac..aa4b6f4f3b5e 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -1117,17 +1117,12 @@ static inline int task_cputime_expired(const struct task_cputime *sample, static inline int fastpath_timer_check(struct task_struct *tsk) { struct signal_struct *sig; - cputime_t utime, stime; - - task_cputime(tsk, &utime, &stime); if (!task_cputime_zero(&tsk->cputime_expires)) { - struct task_cputime task_sample = { - .utime = utime, - .stime = stime, - .sum_exec_runtime = tsk->se.sum_exec_runtime - }; + struct task_cputime task_sample; + task_cputime(tsk, &task_sample.utime, &task_sample.stime); + task_sample.sum_exec_runtime = tsk->se.sum_exec_runtime; if (task_cputime_expired(&task_sample, &tsk->cputime_expires)) return 1; }