linux-kernel - Re: [GIT PULL 0/9] perf/core improvements and fixes

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Message-ID: <CAMsRxfLsMdrSSd4GQBuDDJGC7jc0=gJFvmMaFKzAafu53A6KBA@mail.gmail.com>
Date:	Sat, 27 Oct 2012 19:12:06 +0200
From:	stephane eranian <eranian@...glemail.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	David Ahern <dsahern@...il.com>, Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	linux-kernel@...r.kernel.org, Andrew Vagin <avagin@...nvz.org>,
	Borislav Petkov <bp@...64.org>,
	David Howells <dhowells@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Steven Rostedt <rostedt@...dmis.org>, arnaldo.melo@...il.com,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [GIT PULL 0/9] perf/core improvements and fixes

On Fri, Oct 26, 2012 at 5:31 PM, Namhyung Kim <namhyung@...nel.org> wrote:
> 2012-10-26 (금), 09:06 -0600, David Ahern:
>> On 10/26/12 8:54 AM, Ingo Molnar wrote:
>> >> perf/core improvements:
>> >>
>> >> . perf inject changes to allow showing where a task sleeps, from Andrew Vagin.
>> >>
>> >> . Makefile improvements from Namhyung Kim.
>> >
>> > These are really useful: there used to be a couple of seconds of
>> > wait time at the beginning of every perf build - these are now
>> > nicely explained with the various CHK entries.
>
> Kudos to Jiri who did the real work!
>
>>
>> PERF-VERSION-GEN and specifically the git commands are the cause of more
>> delay than the config checks, especially when doing the build in a VM
>> with the kernel source on an NFS mount.
>
> And I see a strange delay when compiling builtin-sched.o.  After
> building perf tools, I deleted builtin-{sched,test,script}.o to rebuild
> the only since they are largest ones.
>
Yes, I see that delay on copiling builtin-sched.c on my IVB system.
Don't know why it takes a significant number of seconds to compile
this file. It did not use to be like that a few revisions back. It takes
about 8 seconds on my OC'd IVB (> 4GHz).  I don't see much code
in that file.

>   namhyung@...nhard:perf$ ls -lS *.c | head -3
>   -rw-r--r-- 1 namhyung namhyung 45522 2012-10-27 00:20 builtin-sched.c
>   -rw-r--r-- 1 namhyung namhyung 36372 2012-10-27 00:20 builtin-test.c
>   -rw-r--r-- 1 namhyung namhyung 35555 2012-10-27 00:20 builtin-script.c
>
>   namhyung@...nhard:perf$ rm builtin-{sched,test,script}.o
>
>
> And then building each file with time command shows this:
>
>   namhyung@...nhard:perf$ time make builtin-script.o &> /dev/null
>
>   real  0m4.577s
>   user  0m2.755s
>   sys   0m1.655s
>
>   namhyung@...nhard:perf$ time make builtin-test.o &> /dev/null
>
>   real  0m4.486s
>   user  0m2.707s
>   sys   0m1.658s
>
>   namhyung@...nhard:perf$ time make builtin-sched.o &> /dev/null
>
>   real  0m16.936s
>   user  0m15.157s
>   sys   0m1.635s
>
> You can see it easily when building perf without -j option. But I have
> no idea why it takes so long..
>
> Thanks,
> Namhyung
>
>
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