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

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Date:   Mon, 5 Dec 2016 19:57:43 -0800
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: [PATCH 04/10] perf sched timehist: Split is_idle_sample()

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.