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Subject: Re: [PATCHSET 0/6] perf sched timehist: Introduce --idle-hist option
 (v2)
To: Namhyung Kim <namhyung@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>
References: <20161208144755.16673-1-namhyung@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
        Jiri Olsa <jolsa@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Andi Kleen <andi@firstfloor.org>, Minchan Kim <minchan@kernel.org>
From: David Ahern <dsahern@gmail.com>
Message-ID: <00499939-48a7-217d-8127-47763abf5fbd@gmail.com>
Date: Sat, 10 Dec 2016 09:32:54 -0700
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On 12/8/16 7:47 AM, Namhyung Kim wrote:
> Hi,
> 
> This patchset implements the idle hist feature which analyze reason of system
> idle.  Sometimes I need to investigate what makes CPUs to go idle even though
> I have jobs to do.  It may be due to I/O, waiting on lock or whatever.
> 

...

> Namhyung Kim (6):
>   perf sched timehist: Split is_idle_sample()
>   perf sched timehist: Introduce struct idle_time_data
>   perf sched timehist: Save callchain when entering idle
>   perf sched timehist: Skip non-idle events when necessary
>   perf sched timehist: Add -I/--idle-hist option
>   perf sched timehist: Show callchains for idle stat
> 
>  tools/perf/Documentation/perf-sched.txt |   4 +
>  tools/perf/builtin-sched.c              | 252 +++++++++++++++++++++++++++-----
>  2 files changed, 222 insertions(+), 34 deletions(-)
> 

LGTM

Acked-by: David Ahern <dsahern@gmail.com>

Suggested improvement: Add the length of the time window. ie., data collected (or analyzed over if --time is used) for N.M seconds. Puts the amount of idle time into perspective.