linux-kernel - Re: [PATCH 1/2] nohz: move NOHZ code bits out of io_schedule{,

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Message-ID: <20140429151317.GC6129@localhost.localdomain>
Date:	Tue, 29 Apr 2014 17:13:19 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Denys Vlasenko <dvlasenk@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	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>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH 1/2] nohz: move NOHZ code bits out of
 io_schedule{,_timeout} into a helper

On Fri, Apr 25, 2014 at 08:57:29PM +0200, Denys Vlasenko wrote:
> Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
> Cc: Fernando Luis Vazquez Cao <fernando_b1@....ntt.co.jp>
> Cc: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Arjan van de Ven <arjan@...ux.intel.com>
> Cc: Oleg Nesterov <oleg@...hat.com>
> ---
>  kernel/sched/core.c | 33 +++++++++++++++++----------------
>  1 file changed, 17 insertions(+), 16 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index ffea757..3137980 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -4208,6 +4208,21 @@ EXPORT_SYMBOL_GPL(yield_to);
>   * This task is about to go to sleep on IO. Increment rq->nr_iowait so
>   * that process accounting knows that this is a task in IO wait state.
>   */
> +#ifdef CONFIG_NO_HZ_COMMON
> +static __sched void io_wait_end(struct rq *rq)
> +{
> +	if (atomic_dec_and_test(&rq->nr_iowait)) {
> +		if (raw_smp_processor_id() != cpu_of(rq))
> +			tick_nohz_iowait_to_idle(cpu_of(rq));
> +	}
> +}
> +#else
> +static inline void io_wait_end(struct rq *rq)
> +{
> +	atomic_dec(&rq->nr_iowait);
> +}
> +#endif
> +
>  void __sched io_schedule(void)
>  {
>  	struct rq *rq = raw_rq();
> @@ -4218,14 +4233,7 @@ void __sched io_schedule(void)
>  	current->in_iowait = 1;
>  	schedule();
>  	current->in_iowait = 0;
> -#ifdef CONFIG_NO_HZ_COMMON
> -	if (atomic_dec_and_test(&rq->nr_iowait)) {
> -		if (raw_smp_processor_id() != cpu_of(rq))
> -			tick_nohz_iowait_to_idle(cpu_of(rq));
> -	}
> -#else
> -	atomic_dec(&rq->nr_iowait);
> -#endif
> +	io_wait_end(rq);
>  	delayacct_blkio_end();

There is much more to unify that the iowait accounting between all
the io_schedule() declensions.

Peterz I think you had a patch to unify that a few month ago?
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