linux-kernel - Re: [GIT PULL 0/8] Annotation weekly ponies delivery

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Date:	Mon, 14 May 2012 13:13:20 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.org>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>, arnaldo.melo@...il.com,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [GIT PULL 0/8] Annotation weekly ponies delivery

On Sat, 2012-05-12 at 13:40 -0700, Linus Torvalds wrote:
> The whole "-e cycles:pp" doesn't work any more. I don't get any nice
> PEBS information, I get the totally useless irq-based profiling.
> 
> The difference for a "make -j" profile is quite stunning:
> 
> Doing "perf record -f -e cycles:pp -F 20000 make -j"
> 
>  - my current git:
> 
>     [ perf record: Woken up 47 times to write data ]
>     [ perf record: Captured and wrote 11.890 MB perf.data (~519462 samples) ]
> 
>  - with the above tree pulled into my current git tree (but compiling
> the same old tree):
> 
>     [ perf record: Woken up 1 times to write data ]
>     [ perf record: Captured and wrote 0.031 MB perf.data (~1375 samples) ] 

The output simply suggests we're not getting enough samples not that
PEBS isn't working, in fact I can could reproduce without using PEBS.

This bisected to the below commit, the code has since been changed again
and all that evlist stuff gives me a head-ache. Acme, Namhyung ?


55261f46702cec96911a81aacfb3cba13434d304 is the first bad commit
commit 55261f46702cec96911a81aacfb3cba13434d304
Author: Namhyung Kim <namhyung.kim@....com>
Date:   Mon May 7 14:08:59 2012 +0900

    perf evlist: Fix creation of cpu map
    
    Currently, 'perf record -- sleep 1' creates a cpu map for all online
    cpus since it turns out calling cpu_map__new(NULL). Fix it.
    
    Also it is guaranteed that cpu_list is NULL if PID/TID is given by
    calling perf_target__validate(), so we can make the conditional bit
    simpler.
    
    This also fixes perf test 7 (Validate) failure on my 6 core machine:
    
      $ cat /sys/devices/system/cpu/online
      0-11
      $ ./perf test -v 7
       7: Validate PERF_RECORD_* events & perf_sample fields:
      --- start ---
      perf_evlist__mmap: Operation not permitted
      ---- end ----
      Validate PERF_RECORD_* events & perf_sample fields: FAILED!
    
    Signed-off-by: Namhyung Kim <namhyung.kim@....com>
    Reviewed-by: David Ahern <dsahern@...il.com>
    Cc: David Ahern <dsahern@...il.com>
    Cc: Ingo Molnar <mingo@...hat.com>
    Cc: Namhyung Kim <namhyung@...il.com>
    Cc: Paul Mackerras <paulus@...ba.org>
    Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
    Link: http://lkml.kernel.org/r/1336367344-28071-3-git-send-email-namhyung.kim@lge.com
    Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>


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