linux-kernel - Re: [PATCH v5 06/20] perf: Add AUX record

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Message-ID: <87fvegdw7e.fsf@ashishki-desk.ger.corp.intel.com>
Date:	Wed, 22 Oct 2014 17:18:29 +0300
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Robert Richter <rric@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>, kan.liang@...el.com,
	adrian.hunter@...el.com, acme@...radead.org,
	mathieu.poirier@...aro.org
Subject: Re: [PATCH v5 06/20] perf: Add AUX record

Peter Zijlstra <peterz@...radead.org> writes:

> On Mon, Oct 13, 2014 at 04:45:34PM +0300, Alexander Shishkin wrote:
>> +	/*
>> +	 * Records that new data landed in the AUX buffer part.
>> +	 *
>> +	 * struct {
>> +	 * 	struct perf_event_header	header;
>> +	 *
>> +	 * 	u64				aux_offset;
>> +	 * 	u64				aux_size;
>> +	 *	u64				flags;
>> +	 * 	struct sample_id		sample_id;
>> +	 * };
>> +	 */
>> +	PERF_RECORD_AUX				= 11,
>
> Given the discussion with the ARM people the last time, do we want to
> add the possibility of a variable data field in this event? Its easy to
> add now, harder to do later (although not impossible).

Iirc, what they want is to save a once-per-session chunk of data, which
would be better synthesized by perf record than sent from a pmu driver?

We do something like that with PT right now, perf record looks at pmu's
sysfs attributes and stores them in some synthesized record.

> Also added Mathieu Poirier on CC, he asked to be included in your next
> postings.

Indeed, my apologies.

Regards,
--
Alex
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