linux-kernel - Re: [PATCH 7/7] event: add tracepoint for accounting block time

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Date:	Mon, 28 Nov 2011 12:42:11 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Andrew Vagin <avagin@...nvz.org>
Cc:	linux-kernel@...r.kernel.org, paulus@...ba.org, mingo@...e.hu,
	acme@...stprotocols.net, asharma@...com, devel@...nvz.org,
	dsahern@...il.com, linux-perf-users@...r.kernel.org,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [PATCH 7/7] event: add tracepoint for accounting block time

On Mon, 2011-11-28 at 12:03 +0300, Andrew Vagin wrote:
> This tracepoint shows how long a task is sleeping in uninterruptible state.
> 
> E.g.
> It may show how long and where a mutex is waited.

Fair enough, makes one wonder how much it would take to make
account_scheduler_latency() go away..

> Signed-off-by: Andrew Vagin <avagin@...nvz.org>
> ---
>  include/trace/events/sched.h |    7 +++++++
>  kernel/sched_fair.c          |    2 ++
>  2 files changed, 9 insertions(+), 0 deletions(-)
> 
> diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
> index 959ff18..be077cf 100644
> --- a/include/trace/events/sched.h
> +++ b/include/trace/events/sched.h
> @@ -331,6 +331,13 @@ DEFINE_EVENT(sched_stat_template, sched_stat_iowait,
>  	     TP_ARGS(tsk, delay));
>  
>  /*
> + * Tracepoint for accounting block time (time the task is in uninterruptible).
> + */
> +DEFINE_EVENT(sched_stat_template, sched_stat_block,
> +	     TP_PROTO(struct task_struct *tsk, u64 delay),
> +	     TP_ARGS(tsk, delay));
> +
> +/*
>   * Tracepoint for accounting runtime (time the task is executing
>   * on a CPU).
>   */
> diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
> index 5c9e679..0d7b156 100644
> --- a/kernel/sched_fair.c
> +++ b/kernel/sched_fair.c
> @@ -907,6 +907,8 @@ static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
>  				trace_sched_stat_iowait(tsk, delta);
>  			}
>  
> +			trace_sched_stat_block(tsk, delta);
> +
>  			/*
>  			 * Blocking time is in units of nanosecs, so shift by
>  			 * 20 to get a milliseconds-range estimation of the

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