linux-kernel - Re: [PATCH V5 0/9] perf: Driver specific configuration for PMU

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Message-ID: <CANLsYkxQNB-ZU6obSKvJZMMmZQT5kMfuUuA1PpF8YYeZqujwbQ@mail.gmail.com>
Date:   Tue, 23 Aug 2016 08:51:35 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        jolsa@...nel.org, Ingo Molnar <mingo@...hat.com>,
        Vince Weaver <vince@...ter.net>,
        Michael Kerrisk-manpages <mtk.manpages@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH V5 0/9] perf: Driver specific configuration for PMU

On 22 August 2016 at 09:15, Alexander Shishkin
<alexander.shishkin@...ux.intel.com> wrote:
> Mathieu Poirier <mathieu.poirier@...aro.org> writes:
>
>> As such something that used to be a two-step process:
>>
>> # echo 1 > /sys/bus/coresight/devices/20070000.etr/enable_sink
>> # perf record -e cs_etm//u --per-thread  uname
>>
>> is integrated in a single command:
>>
>> # perf record -e cs_etm/@...k=20070000.etr/u --per-thread  uname
>
> Can't we simply teach perf record to write 1 to that sysfs attribute and
> avoid parsing more ascii strings in the kernel? I suspect that would also
> take way less code.

That, in my opinion, would be a big hack.  Peter and Jiri, any thoughts on this?

>
> Are there any other use cases for this besides specifying @sink for a
> ETM?

Not at this time but there is so many configuration option for the
ETM/PTM tracers (that aren't filters) that I wanted the right
infrastructure to be there should/when we need to expand.

Thanks for taking the time to review this set,
Mathieu

>
> Regards,
> --
> Alex