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

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Date:   Mon, 20 Feb 2017 18:22:54 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
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

Em Mon, Feb 20, 2017 at 09:31:49PM +0100, Borislav Petkov escreveu:
> 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

Well, this one should be read (and written in the tool output as):

<not supported in workload only mode, try system wide, using -a>

> 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>.

Right, the ENOTSUPP in this case needs to be properly expanded into
something meaningful, as suggested above.

> 
> Thoughts?
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> Good mailing practices for 400: avoid top-posting and trim the reply.