linux-kernel - Re: [PATCH v2] perf: Suppress AUX/OVERWRITE records

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Message-ID: <20180504120959.z6cik4zv6ragblxd@um.fi.intel.com>
Date:   Fri, 4 May 2018 15:09:59 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        linux-kernel@...r.kernel.org, Will Deacon <will.deacon@....com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Markus Metzger <markus.t.metzger@...el.com>
Subject: Re: [PATCH v2] perf: Suppress AUX/OVERWRITE records

On Wed, Apr 04, 2018 at 05:53:23PM +0300, Alexander Shishkin wrote:
> It has been pointed out to me many times that it is useful to be able
> to switch off AUX records to save the bandwidth for records that actually
> matter, for example, in AUX overwrite mode.
> 
> The usefulness of PERF_RECORD_AUX is in some of its flags, like the
> TRUNCATED flag that tells the decoder where exactly gaps in the trace are.
> The OVERWRITE flag, on the other hand will be set on every single record
> in overwrite mode. However, a PERF_RECORD_AUX[flags=OVERWRITE] is
> generated on every target task's sched_out, which over time adds up to
> a lot of useless information.
> 
> If any folks out there have userspace that depends on a constant stream of
> OVERWRITE records for a good reason, they'll have to let us know.
> 
> Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Cc: Markus Metzger <markus.t.metzger@...el.com>
> Cc: Adrian Hunter <adrian.hunter@...el.com>

This one seems to be slipping through the cracks.

Cheers,
--
Alex