linux-kernel - Re: [PATCH V2 12/15] perf tools: allow non-matching sample types

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Date:	Mon, 01 Jul 2013 12:53:55 -0600
From:	David Ahern <dsahern@...il.com>
To:	Adrian Hunter <adrian.hunter@...el.com>
CC:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>, Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH V2 12/15] perf tools: allow non-matching sample types

On 7/1/13 3:32 AM, Adrian Hunter wrote:
> Snip
>
>>
>> While this works for a combined S/W and tracepoint events session, I do not
>> like promoting sample types to the minimum compatible level for all events
>> in the session. perf needs to allow each event to have its own sample_type
>> and not force a minimal compatibility.
>
> Why?  The impact is small. The kernel API is completely unchanged.

I'd like to see libperf become a stable, usable library - usable by more 
than the perf binary and its builtin commands. I have already done this 
once for a daemon, and it was a PITA to get the specific use functional 
without memory leaks/growth in the libperf part.

With respect to this specific patch it means appropriate flexibility in 
the data collected for events. ie., each event can have its own 
sample_type. For example if the tracepoint already contains task 
information TID is not needed - and IP may not be wanted either. The 
code processing the samples should not require all events to have some 
minimum data format - that just wastes buffer space.

David

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