linux-kernel - Re: [RFC 0/5] perf tools: Minimalistic build without libelf dependency

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Date:	Tue, 15 May 2012 09:40:21 +0900
From:	Namhyung Kim <namhyung.kim@....com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 0/5] perf tools: Minimalistic build without libelf dependency

Hi,

On Mon, 14 May 2012 11:22:07 +0200, Ingo Molnar wrote:
> * Namhyung Kim <namhyung.kim@....com> wrote:
>
>> Hi,
>> 
>> NOTE: This is a RFC patchset and it contains a lot of rough edges
>> and ugly codes.
>> 
>> Current build procedure of perf tools requires a couple of external
>> libraries. Although most of them are optional, elfutils' libelf is
>> mandatory for resolving symbols and build-id of the binaries being
>> profiled. For some reason, it makes embedded guys' life harder who
>> want to build and run perf tools on their boards.
>
> Yeah, and this is a very useful patchset from that perspective.
>

Glad to hear that :).


>> This patch set tries to fix the problem by letting the perf could
>> be built without libelf. The initial intent was just providing
>> perf record command to gather performance events interested on the
>> system and copies the data to development box to be used by perf
>> report for analysis.
>> 
>> However it's changed to have most of perf commands as is because
>> perf can resolve kernel symbols without libelf and many of perf
>> commands deal (mostly) with kernel events - so no need to restrict
>> capability of perf tools. Therefore, the end result is not so
>> minimalistic in fact and only thing it cannot do is "perf probe".
>>
>> And then I realized that the perf record needs to know about the
>> build-id's anyway :(. So I implemented a poor man's version of elf
>> parser only for parsing the build-id info.
>> 
>> To build a minimal perf tools, pass MINIMAL=1 to make. The perf
>> report will not display symbol names:
>
> Could we make this automatic when the required elf libraries are 
> not present?
>

Yes, I think it's doable.

Thanks,
Namhyung
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