linux-kernel - Re: BFS vs. mainline scheduler benchmarks and measurements

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Date:	Thu, 10 Sep 2009 13:35:16 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Mike Galbraith <efault@....de>
Cc:	Ingo Molnar <mingo@...e.hu>, Nikos Chantziaras <realnc@...or.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Con Kolivas <kernel@...ivas.org>, linux-kernel@...r.kernel.org
Subject: Re: BFS vs. mainline scheduler benchmarks and measurements

On Thu, Sep 10 2009, Mike Galbraith wrote:
> On Thu, 2009-09-10 at 13:24 +0200, Jens Axboe wrote:
> > On Thu, Sep 10 2009, Mike Galbraith wrote:
> 
> > > xmodmap doesn't seem to be running in this sample.
> > 
> > That's weird, it was definitely running. I did:
> > 
> > sleep 1; xmodmap .xmodmap-carl
> > 
> > in one xterm, and then switched to the other and ran the sched_debug
> > dump. I have to do it this way, as X will not move focus once xmodmap
> > starts running. It could be that xmodmap is mostly idle, and the real
> > work is done by Xorg and/or xfwm4 (my window manager).
> 
> Hm.  Ok, I'll crawl over it, see if anything falls out.

That seems to be confirmed with the low context switch rate of the perf
stat of xmodmap. If I run perf stat -a to get a system wide collection
for xmodmap, I get:

 Performance counter stats for 'xmodmap .xmodmap-carl':

   20112.060925  task-clock-msecs         #      1.998 CPUs 
         629360  context-switches         #      0.031 M/sec
              8  CPU-migrations           #      0.000 M/sec
          13489  page-faults              #      0.001 M/sec
  <not counted>  cycles                  
  <not counted>  instructions            
  <not counted>  cache-references        
  <not counted>  cache-misses            

   10.067532449  seconds time elapsed

And again, system is idle while this is happening. Can't rule out that
this is some kind of user space bug of course.

-- 
Jens Axboe

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