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

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Date:   Mon, 20 Feb 2017 23:47:16 +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

On Mon, Feb 20, 2017 at 06:22:54PM -0300, Arnaldo Carvalho de Melo wrote:
> Well, this one should be read (and written in the tool output as):
> 
> <not supported in workload only mode, try system wide, using -a>

Do you want to change that CNTR_NOT_SUPPORTED string unconditionally to
something like above?

Because perf_evsel.supported seems like it means that counter is not
supported but not necessarily only because of the missing -a for an
uncore event, AFAICT. I could be wrong.

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

I dumped errno in __run_perf_stat():

./perf stat -v -e amd_nb/event=0xe0,umask=0x1f/ sleep 1
Using CPUID AuthenticAMD-21-2
Warning:
amd_nb/event=0xe0,umask=0x1f/ event is not supported by the kernel: 22.

It is -EINVAL and the syscall returns -EINVAL in bunch of places so I'm
guessing this might not be a good way to match the retval to the proper
error message.

Peterz said something about scanning all events supplied by -e and if
all are uncore, to set -a automatically. Can we do that?

-- 
Regards/Gruss,
    Boris.

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