From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1752144AbbCWHWV (ORCPT <rfc822;w@1wt.eu>);
	Mon, 23 Mar 2015 03:22:21 -0400
Received: from mail-wi0-f172.google.com ([209.85.212.172]:35324 "EHLO
	mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751416AbbCWHWS (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 23 Mar 2015 03:22:18 -0400
Date: Mon, 23 Mar 2015 08:22:14 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>, Jiri Olsa <jolsa@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>, David Ahern <dsahern@gmail.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Stephane Eranian <eranian@google.com>
Subject: Re: [RFC/PATCH] perf record: Save build-id of DSO in callchains
Message-ID: <20150323072213.GB22765@gmail.com>
References: <1427073483-7713-1-git-send-email-namhyung@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1427073483-7713-1-git-send-email-namhyung@kernel.org>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


* Namhyung Kim <namhyung@kernel.org> wrote:

> Currently the build-id only recorded for sampled location, but in
> order to correctly view/annotate callchains it might need the
> build-id's of callchains too.  I guess this choice was due to a
> performance impact on the post-processing at perf record time.
> 
> Add a new option --buildid-callchain to record this info.
> 
> $ perf record -o xxx -g -- perf > /dev/null
> $ perf buildid-list -i xxx
> 6ebcee76c4b04895598b4df86ec445c49fc137a2 /lib/modules/3.18.6-1-ARCH/build/vmlinux
> fc0759b71584d2513b04f1b530965a61b5e499e2 /usr/lib/ld-2.21.so
> 
> $ perf record -o yyy -g --buildid-callchain -- perf > /dev/null
> $ perf buildid-list -i yyy
> 6ebcee76c4b04895598b4df86ec445c49fc137a2 /lib/modules/3.18.6-1-ARCH/build/vmlinux
> 4235ae90856f98d2746529648a3339ebfa6ede43 /home/namhyung/project/linux/tools/perf/perf
> fc0759b71584d2513b04f1b530965a61b5e499e2 /usr/lib/ld-2.21.so
> 9ac81172d5ff96f40d984fe7c10073a98f1a6b2e /usr/lib/libc-2.21.so
> 864583bb881db1d260660a30a51b3f5022cd538b /usr/lib/libnuma.so.1.0.0

Just curious, could you try to measure the performance impact of this 
change?

Also, unless the performance (or file size) effect is horrible, I 
think this flag should be implicitly set by -g.

99.999% of users won't know about this flag, and will see broken 
annotations!

Thanks,

	Ingo