linux-kernel - Re: [PATCHSET 0/6] perf sched timehist: Introduce --idle-hist option (v2)

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Message-ID: <00499939-48a7-217d-8127-47763abf5fbd@gmail.com>
Date:   Sat, 10 Dec 2016 09:32:54 -0700
From:   David Ahern <dsahern@...il.com>
To:     Namhyung Kim <namhyung@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Olsa <jolsa@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andi Kleen <andi@...stfloor.org>,
        Minchan Kim <minchan@...nel.org>
Subject: Re: [PATCHSET 0/6] perf sched timehist: Introduce --idle-hist option
 (v2)

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@...il.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.