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

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Date:	Mon, 21 May 2012 15:00:55 +0900
From:	Namhyung Kim <namhyung.kim@....com>
To:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Stephane Eranian <eranian@...gle.com>,
	Jiri Olsa <jolsa@...hat.com>
Subject: Re: [RFC 0/5] perf tools: Minimalistic build without libelf dependency

Hi, all

Any other comments for this?


Thanks,
Namhyung


On Mon, 14 May 2012 16:10:19 +0900, Namhyung Kim wrote:
> 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.
>
> 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:
>
>  # Samples: 988  of event 'cycles'
>  # Event count (approx.): 3726465542
>  #
>  # Overhead  Command      Shared Object                     Symbol
>  # ........  .......  .................  .........................
>  #
>      98.40%  noploop  noploop            [.] 0x000000000000066d   
>       1.35%  noploop  ld-2.15.so         [.] 0x000000000000bab1   
>       0.10%  noploop  [kernel.kallsyms]  [k] native_write_msr_safe
>       0.10%  noploop  [kernel.kallsyms]  [k] scheduler_tick       
>       0.03%  noploop  [kernel.kallsyms]  [k] bad_range            
>       0.01%  noploop  [kernel.kallsyms]  [k] pipe_read            
>
> But perf buildid-list can show you the build-id's:
>
>  $ ./perf buildid-list
>  ebfc1bdb98999c64d36ddfe394c58df3de6cbcfb [kernel.kallsyms]
>  52f0c5f25b95075e6fd7682763f7c3a779a4e889 /usr/lib64/ld-2.15.so
>  43a7a2b399b6ee2ff29c6bdadbda6bff88712ed4 /home/namhyung/bin/noploop
>
> So it can be packed using perf archive so copied and analized
> with full-fledged perf tools on a development machine.
>
> This patchset is based on commit cb04ff9ac424 ("sched, perf: Use
> a single callback into the scheduler") and tested on x86_64 and arm.
>
> Any comments are welcome, thanks.
> Namhyung
>
>
> Namhyung Kim (5):
>   perf symbols: Introduce symbol__elf_init()
>   perf symbols: Do not use ELF's symbol binding constants
>   perf tools: Split out util/symbol-elf.c
>   perf tools: Support minimal build
>   perf symbols: Implement poor man's ELF parser
>
>  tools/perf/Makefile                 |   29 ++
>  tools/perf/builtin-buildid-list.c   |    4 +-
>  tools/perf/builtin-top.c            |    5 +-
>  tools/perf/command-list.txt         |    2 +-
>  tools/perf/perf.c                   |    2 +
>  tools/perf/ui/browsers/map.c        |    5 +-
>  tools/perf/util/elf-minimal.h       |  153 ++++++++
>  tools/perf/util/generate-cmdlist.sh |   15 +
>  tools/perf/util/symbol-elf.c        |  691 +++++++++++++++++++++++++++++++++
>  tools/perf/util/symbol-minimal.c    |  258 +++++++++++++
>  tools/perf/util/symbol.c            |  712 ++---------------------------------
>  tools/perf/util/symbol.h            |   20 +
>  12 files changed, 1195 insertions(+), 701 deletions(-)
>  create mode 100644 tools/perf/util/elf-minimal.h
>  create mode 100644 tools/perf/util/symbol-elf.c
>  create mode 100644 tools/perf/util/symbol-minimal.c
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