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

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Date:	Thu, 10 Sep 2009 09:53:58 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mike Galbraith <efault@....de>,
	Con Kolivas <kernel@...ivas.org>, linux-kernel@...r.kernel.org
Subject: Re: BFS vs. mainline scheduler benchmarks and measurements

On Thu, Sep 10 2009, Ingo Molnar wrote:
> 
> * Jens Axboe <jens.axboe@...cle.com> wrote:
> 
> > On Thu, Sep 10 2009, Jens Axboe wrote:
> > > On Thu, Sep 10 2009, Peter Zijlstra wrote:
> > > > On Wed, 2009-09-09 at 14:20 +0200, Jens Axboe wrote:
> > > > > 
> > > > > One thing I also noticed is that when I have logged in, I 
> > > > > run xmodmap manually to load some keymappings (I always tell 
> > > > > myself to add this to the log in scripts, but I 
> > > > > suspend/resume this laptop for weeks at the time and forget 
> > > > > before the next boot). With the stock kernel, xmodmap will 
> > > > > halt X updates and take forever to run. With BFS, it 
> > > > > returned instantly. As I would expect.
> > > > 
> > > > Can you provide a little more detail (I'm a xmodmap n00b), how does one
> > > > run xmodmap and maybe provide your xmodmap config?
> > > 
> > > Will do, let me get the notebook and strace time it on both bfs and
> > > mainline.
> > 
> > Here's the result of running perf stat xmodmap .xmodmap-carl on 
> > the notebook. I have attached the .xmodmap-carl file, it's pretty 
> > simple. I have also attached the output of strace -o foo -f -tt 
> > xmodmap .xmodmap-carl when run on 2.6.31-rc9.
> > 
> > 2.6.31-rc9-bfs210
> > 
> >  Performance counter stats for 'xmodmap .xmodmap-carl':
> > 
> >      153.994976  task-clock-msecs         #      0.990 CPUs   (scaled from 99.86%)
> >               0  context-switches         #      0.000 M/sec  (scaled from 99.86%)
> >               0  CPU-migrations           #      0.000 M/sec  (scaled from 99.86%)
> >             315  page-faults              #      0.002 M/sec  (scaled from 99.86%)
> >   <not counted>  cycles                  
> >   <not counted>  instructions            
> >   <not counted>  cache-references        
> >   <not counted>  cache-misses            
> > 
> >     0.155573406  seconds time elapsed
> 
> (Side question: what hardware is this - why are there no hw 
> counters? Could you post the /proc/cpuinfo?)

Sure, attached. It's a Thinkpad x60, core duo. Nothing fancy. The perf
may be a bit dated.

I went to try -tip btw, but it crashes on boot. Here's the backtrace,
typed manually, it's crashing in queue_work_on+0x28/0x60.

Call Trace:
        queue_work
        schedule_work
        clocksource_mark_unstable
        mark_tsc_unstable
        check_tsc_sync_source
        native_cpu_up
        relay_hotcpu_callback
        do_forK_idle
        _cpu_up
        cpu_up
        kernel_init
        kernel_thread_helper

> >  Performance counter stats for 'xmodmap .xmodmap-carl':
> > 
> >        8.529265  task-clock-msecs         #      0.001 CPUs 
> >              23  context-switches         #      0.003 M/sec
> >               1  CPU-migrations           #      0.000 M/sec
> >             315  page-faults              #      0.037 M/sec
> >   <not counted>  cycles                  
> >   <not counted>  instructions            
> >   <not counted>  cache-references        
> >   <not counted>  cache-misses            
> > 
> >    11.804293482  seconds time elapsed
> 
> Thanks - so we context-switch 23 times - possibly to Xorg. But 11 
> seconds is extremely long. Will try to reproduce it.

There's also the strace info with timings. Xorg is definitely involved,
during those 11s things stop updating completely.

-- 
Jens Axboe

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