linux-kernel - Re: [PATCH -tip v2 2/6] perf bts: Introduce new sub command 'perf bts trace'

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Message-ID: <20101221184516.GP1750@nowhere>
Date:	Tue, 21 Dec 2010 19:45:18 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Akihiro Nagai <akihiro.nagai.hw@...achi.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	2nddept-manager@....hitachi.co.jp,
	Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH -tip v2 2/6] perf bts: Introduce new sub command 'perf
 bts trace'

On Tue, Dec 21, 2010 at 07:40:32PM +0100, Peter Zijlstra wrote:
> On Tue, 2010-12-21 at 19:31 +0100, Frederic Weisbecker wrote:
> > Actually the best would be to select PERF_SAMPLE_ID in the sample_type
> > on record and also PERF_FORMAT_ID in the read_format.
> 
> That would grow the data size for little gain, as long as you only
> record BTS data into the buffer the current bits should work fine.

Indeed.

In the longer term though, I think we need a specific branch set record.

Currently for every branch pair we create a new event with all the headers,
so the pid, time, etc... are all repeated for every entries.

We rather need a single record everytime we flush the bts buffer to the perf
buffer.
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