Date: Wed, 26 Aug 2015 23:57:59 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Jason Low <jason.low2@hp.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Oleg Nesterov <oleg@redhat.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        linux-kernel@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Steven Rostedt <rostedt@goodmis.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Terry Rudd <terry.rudd@hp.com>, Rik van Riel <riel@redhat.com>,
        Scott J Norton <scott.norton@hp.com>
Subject: Re: [PATCH 1/3] timer: Optimize fastpath_timer_check()
Message-ID: <20150826215758.GB11992@lerouge>
References: <1440559068-29680-1-git-send-email-jason.low2@hp.com>
 <1440559068-29680-2-git-send-email-jason.low2@hp.com>
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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
> 
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