linux-kernel - Re: [PATCHv3 00/19] perf tools: Factor ordered samples queue

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Date:	Mon, 21 Jul 2014 09:43:58 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Jiri Olsa <jolsa@...nel.org>, linux-kernel@...r.kernel.org
CC:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Jean Pihet <jean.pihet@...aro.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCHv3 00/19] perf tools: Factor ordered samples queue

On 07/21/2014 12:55 AM, Jiri Olsa wrote:
> hi,
> this patchset factors session's ordered samples queue,
> and allows to limit the size of this queue.
> 
> v3 changes:
>   - rebased to latest tip/perf/core
>   - add comment for WARN in patch 8 (David)
>   - added ordered-events debug variable (David)
>   - renamed ordered_events_(get|put) to ordered_events_(new|delete)
>   - renamed struct ordered_events_queue to struct ordered_events
> 
> v2 changes:
>   - several small changes for review comments (Namhyung)
> 
> 
> The report command queues events till any of following
> conditions is reached:
>   - PERF_RECORD_FINISHED_ROUND event is processed
>   - end of the file is reached
> 
> Any of above conditions will force the queue to flush some
> events while keeping all allocated memory for next events.
> 
> If PERF_RECORD_FINISHED_ROUND is missing the queue will

Why is it missing?

> allocate memory for every single event in the perf.data.
> This could lead to enormous memory consuption and speed
> degradation of report command for huge perf.data files.
> 
> With the quue allocation limit of 100 MB, I've got around
> 15% speedup on reporting of ~10GB perf.data file.

How do you know the results are still valid?  Wouldn't it
be better to wait that extra 15% and know that the data has
been processed correctly?

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