linux-kernel - Re: [PATCH 3/4] nohz: Consolidate sleep time stats read code

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Date:	Sun, 18 Aug 2013 19:00:01 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Fernando Luis Vazquez Cao <fernando_b1@....ntt.co.jp>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [PATCH 3/4] nohz: Consolidate sleep time stats read code

On 08/16, Frederic Weisbecker wrote:
>
> get_cpu_idle_time_us() and get_cpu_iowait_time_us() mostly share
> the same code. Lets consolidate both implementations.

Personally I like every patch which consolidates the code ;)

>  	do {
>  		seq = read_seqcount_begin(&ts->sleeptime_seq);
> -		if (ts->idle_active && !nr_iowait_cpu(cpu)) {
> +		if (io)
> +			sleep = ts->iowait_sleeptime;
> +		else
> +			sleep = ts->idle_sleeptime;
> +
> +		if (ts->idle_active)
> +			continue;
> +
> +		if ((io && nr_iowait_cpu(cpu)) || (!io && !nr_iowait_cpu(cpu))) {
>  			ktime_t delta = ktime_sub(now, ts->idle_entrytime);
> -			idle = ktime_add(ts->idle_sleeptime, delta);
> -		} else {
> -			idle = ts->idle_sleeptime;
> +			sleep = ktime_add(sleep, delta);
>  		}
>  	} while (read_seqcount_retry(&ts->sleeptime_seq, seq));

Cosmetic/subjective, feel free to ignore. but perhaps

		if (ts->idle_active && io == !!nr_iowait_cpu(cpu)) {
			...
		}

looks more understandable.

Oleg.

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