linux-kernel - Re: [PATCHv2 4/5] perf stat: Add -a as a default target

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Message-ID: <20170220203149.yxietgdzi5lxdk5n@pd.tnic>
Date:   Mon, 20 Feb 2017 21:31:49 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...hat.com>, Jiri Olsa <jolsa@...nel.org>,
        David Ahern <dsahern@...il.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCHv2 4/5] perf stat: Add -a as a default target

Btw, I received your mail just now - probably greylisting...

On Mon, Feb 20, 2017 at 10:44:33AM -0300, Arnaldo Carvalho de Melo wrote:
> Isn't this confusing, i.e. people runnin 'tool workload' can be lead to
> think that the events reported took place just when the workload was
> running, i.e. on the same cpu and while it was being scheduled?

That's a good point.

> I understand the desire to avoid asking people to use -a, i.e. if it
> only makes sense as system wide, hey, do it as system wide, but can't
> this be confusing?

Well, I did

tool workload

and it said <not supported>. Now, if I'm the only one to stare puzzled
at this and wonder why it says "not supported", then sure, I know now
that I should use -a.

But if other users are as confused as me, you probably want to tell them
to try -a too, no?

IOW, we probably could extend my other patch which says that people
should try to disable the HW NMI watchdog to say "try using -a for
uncore-only events" when it detects <not supported>.

Thoughts?

-- 
Regards/Gruss,
    Boris.

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