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

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Date:	Sat, 27 Oct 2012 00:31:42 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	David Ahern <dsahern@...il.com>
Cc:	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>,
	Stephane Eranian <eranian@...il.com>,
	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

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.

  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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