linux-kernel - Re: [PATCH V5 3/3] perf tool: check buildid for symoff

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Message-ID: <87d289o0sz.fsf@sejong.aot.lge.com>
Date:	Thu, 27 Nov 2014 11:05:32 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Kan Liang <kan.liang@...el.com>
Cc:	acme@...nel.org, jolsa@...hat.com, linux-kernel@...r.kernel.org,
	ak@...ux.intel.com
Subject: Re: [PATCH V5 3/3] perf tool: check buildid for symoff

Hi Kan,

On Mon, 24 Nov 2014 11:00:29 -0500, Kan Liang wrote:
> From: Kan Liang <kan.liang@...el.com>
>
> symoff can support both same binaries and different binaries. However,
> the offset may be changed for different binaries. This patch checks the
> buildid of perf.data. If they are from different binaries, print a
> warning to notify the user.

Hmm.. I think that perf diff is supposed to compare performance between
different (i.e. modified) binaries.  So there's a little point to print
the warning IMHO - but I'm not insist it strongly..

Anyway, I think what we really need for the warning is different version
of same binary.  For example, if data file 1 has DSO A and B, and data
file 2 has DSO B and C, we should not consider they're different (unless
build-ids of B in data file 1 and 2 are different) since A and C won't
affect symoff comparision.

Thanks,
Namhyung
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