linux-kernel - Re: [PATCH v6 7/7] perf intel-pt: Add brief documentation for PEBS via Intel PT

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Date:   Tue, 13 Aug 2019 19:21:39 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:     Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        kan.liang@...ux.intel.com, Adrian Hunter <adrian.hunter@...el.com>,
        alexander.shishkin@...ux.intel.com
Subject: Re: [PATCH v6 7/7] perf intel-pt: Add brief documentation for PEBS via Intel PT

Arnaldo Carvalho de Melo <acme@...hat.com> writes:

> I've just blindly followed the provided documentation :)

Yes, I should have checked it also before I sent it out. :)

> So you say I should have tried this instead:
>
>   # perf record -c 10000 -e '{intel_pt/branch=0/,cycles/aux-output/ppp}' uname

Right. For the purposes of illustrating the error condition, you can
probably drop the '-c ...' and 'branch=0' also, but either way is fine.

>   Error:
>   The 'aux_output' feature is not supported, update the kernel.

Or it's not supported by the hardware. I don't think we make a
distinction at the moment. You can tell if it's available from dmesg,
but not otherwise.

>   #
>
> Or with leader sampling?
>
>   # perf record -c 10000 -e '{intel_pt/branch=0/,cycles/aux-output/ppp}:S' uname

Not sure if we should even allow this. Maybe Adrian can chime in.

Thanks,
--
Alex