linux-kernel - Re: [PATCH 04/10] perf sched timehist: Split is_idle

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Date:   Wed, 7 Dec 2016 10:26:44 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     David Ahern <dsahern@...il.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        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: [PATCH 04/10] perf sched timehist: Split is_idle_sample()

Hi David,

On Mon, Dec 05, 2016 at 07:57:43PM -0800, David Ahern wrote:
> On 12/5/16 7:40 PM, Namhyung Kim wrote:
> > The is_idle_sample() function actually does more than determining
> > whether sample come from idle task.  Split the callchain part into
> > save_task_callchain() to make it clearer.  Also checking prev_pid from
> > trace data looks unnecessary since it should be always same as
> > sample->pid.
> 
> The timehist command is 3-4 years old now, and over that time it has
> been used on a variety of OS'es -- RHEL6, WRL5, WRL6, various Fedora
> and debian releases, etc. 
> 
> The idle_sample checks were added for a reason. Given the range of
> kernels that have sched tracepoints I'd be wary of just removing it
> regardless of how silly it seems against top of tree kernels.

Hmm.. ok.  Maybe I need to add a comment.

What do you think about moving callchain part then?

Thanks,
Namhyung