linux-kernel - Re: [PATCH 1/3] perf, pt, coresight: Clean up address filter structure

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Date:   Thu, 2 Feb 2017 10:36:35 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Vince Weaver <vince@...ter.net>,
        Stephane Eranian <eranian@...gle.com>,
        Arnaldo Carvalho de Melo <acme@...radead.org>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH 1/3] perf, pt, coresight: Clean up address filter structure

On 2 February 2017 at 03:42, Alexander Shishkin
<alexander.shishkin@...ux.intel.com> wrote:
> Mathieu Poirier <mathieu.poirier@...aro.org> writes:
>
>> Do we have two different syntax to specify the same behaviour?
>>
>> For example we have:
>>
>> --filter 'start 0x80082570/0x644'
>>
>> and
>>
>> --filter 'filter 0x80082570/0x644'
>>
>> Both will end up with filter->filter == 1 and filter->range == 1.
>
> This is another reason why enum action is needed. The difference between
> 'start' and 'filter' is that the former means "start tracing when you
> enter this region until something else stops it";

And what is the "something else here"?

> the latter means
> "trace only inside this region" (that is, start tracing when you branch
> inside this region and stop when you branch outside).

That is indeed how range filters work on CS.

> They cannot be
> treated interchangeably as I originally though. PT supports 'filter', CS
> supports 'start', if I remember right. So we should make sure to
> -EOPNOTSUPP things that we don't actually support.

I already published slides at 2 conferences that uses "filter" for
range filters.  On CS I will have to continue using "filter" and
"start" (when specified with a size element) as one and the same.

>
> Regards,
> --
> Alex