Re: BFS vs. mainline scheduler benchmarks and measurements [LWN.net]

From:		Jens Axboe <jens.axboe-AT-oracle.com>
To:		Mike Galbraith <efault-AT-gmx.de>
Subject:		Re: BFS vs. mainline scheduler benchmarks and measurements
Date:		Thu, 10 Sep 2009 13:35:16 +0200
Cc:		Ingo Molnar <mingo-AT-elte.hu>, Nikos Chantziaras <realnc-AT-arcor.de>, Peter Zijlstra <a.p.zijlstra-AT-chello.nl>, Con Kolivas <kernel-AT-kolivas.org>, linux-kernel-AT-vger.kernel.org

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