Re: [PATCH 1/3] timer: Optimize fastpath_timer_check()

Frederic Weisbecker
2015-08-26T21:58:04Z

On Tue, Aug 25, 2015 at 08:17:46PM -0700, Jason Low wrote:
> 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 <jason.low2@hp.com>

Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>

Thanks.

> ---
> kernel/time/posix-cpu-timers.c | 15 +++++++--------
> 1 files changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
> index 892e3da..02596ff 100644
> --- a/kernel/time/posix-cpu-timers.c
> +++ b/kernel/time/posix-cpu-timers.c
> @@ -1117,16 +1117,15 @@ 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;
> + cputime_t utime, stime;
> +
> + task_cputime(tsk, &utime, &stime);
> + task_sample.utime = utime;
> + task_sample.stime = stime;
> + task_sample.sum_exec_runtime = tsk->se.sum_exec_runtime;
>
> if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
> return 1;
> --
> 1.7.2.5
>