Re: [PATCH V2 12/15] perf tools: allow non-matching sample types
From: Adrian Hunter
Date: Tue Jul 02 2013 - 03:04:03 EST
On 01/07/13 21:53, David Ahern wrote:
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On 7/1/13 3:32 AM, Adrian Hunter wrote:
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> Snip
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>>
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>> While this works for a combined S/W and tracepoint events session, I do not
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>> like promoting sample types to the minimum compatible level for all events
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>> in the session. perf needs to allow each event to have its own sample_type
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>> and not force a minimal compatibility.
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>
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> Why? The impact is small. The kernel API is completely unchanged.
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>
I'd like to see libperf become a stable, usable library - usable by more
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than the perf binary and its builtin commands. I have already done this once
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for a daemon, and it was a PITA to get the specific use functional without
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memory leaks/growth in the libperf part.
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With respect to this specific patch it means appropriate flexibility in the
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data collected for events. ie., each event can have its own sample_type. For
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example if the tracepoint already contains task information TID is not
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needed - and IP may not be wanted either. The code processing the samples
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should not require all events to have some minimum data format - that just
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wastes buffer space.
It would be more compelling to provide a use-case where that "waste"
actually makes any difference.
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