Re: sched regression introduced by NO_NEW_FAIR_SLEEPERS

[Ingo Molnar]

* drago01 <drago01@xxxxxxxxx> wrote:

> On Sun, Sep 27, 2009 at 9:47 PM, drago01 <drago01@xxxxxxxxx> wrote:
> > Hi,
> >
> > Chuck has backported some scheduler patches from 2.6.32 to the fedora kernel.
> >
> > I did the following test to test the new scheduler (cpu is a core i7
> > 920 4 cores + HT).
> >
> > run 8 "md5sum /dev/urandom" task and try to use the desktop (compiz).
> >
> > The result was that moving windows or rotating the cube is very slow.
> > (same happens with pure metacity but is is worse in compiz).
> >
> > Mounting debugfs and doing "echo NEW_FAIR_SLEEPERS > sched_features"
> > results into a useable desktop while the 8 md5sum tasks are running
> > (ie. the system behaves as if they where not running at all from an
> > interactivity pov).
> >
> >
> > P.S: please CC me when replying.
> >
> 
> With "NEW_FAIR_SLEEPERS" I can even run 100(!)  "md5sum" task without 
> any effect on interactivity. (still have not found a number of tasks 
> needed to make the system unresponsive as with 8 with 
> "NO_NEW_FAIR_SLEEPERS".

Can you try the latest -tip tree please:

  http://people.redhat.com/mingo/tip.git/README

There we default to FAIR_SLEEPERS + GENTLE_FAIR_SLEEPERS - which should 
give much of the new-fair-sleepers advantage.

There's also a new tool, 'perf sched', which you can install via:

  cd tools/perf/
  make -j install

And use like this to measure latencies in the system:

 $ perf sched record sleep 1
 [ perf record: Woken up 1 times to write data ]
 [ perf record: Captured and wrote 0.059 MB perf.data (~2563 samples) ]

 $ perf sched latency

 -----------------------------------------------------------------------------------------
  Task                  |   Runtime ms  | Switches | Average delay ms | Maximum delay ms |
 -----------------------------------------------------------------------------------------
  events/12:47          |      0.007 ms |        1 | avg:    0.054 ms | max:    0.054 ms |
  events/2:37           |      0.128 ms |        1 | avg:    0.016 ms | max:    0.016 ms |
  at-spi-registry:3292  |      0.752 ms |       20 | avg:    0.015 ms | max:    0.023 ms |
  Xorg:3161             |      0.519 ms |       20 | avg:    0.015 ms | max:    0.024 ms |
  perf:19070            |     21.241 ms |        5 | avg:    0.012 ms | max:    0.019 ms |
  events/1:36           |      0.009 ms |        1 | avg:    0.009 ms | max:    0.009 ms |
  hald-addon-stor:2790  |      0.204 ms |        9 | avg:    0.009 ms | max:    0.011 ms |
  scsi_eh_5:1072        |      0.200 ms |       12 | avg:    0.009 ms | max:    0.009 ms |
  events/0:35           |      0.007 ms |        1 | avg:    0.008 ms | max:    0.008 ms |
  ksoftirqd/12:28       |      0.088 ms |        5 | avg:    0.005 ms | max:    0.009 ms |
  sleep:19071           |      0.668 ms |        3 | avg:    0.005 ms | max:    0.008 ms |
  migration/13:29       |      0.000 ms |        1 | avg:    0.003 ms | max:    0.003 ms |
 -----------------------------------------------------------------------------------------
  TOTAL:                |     23.824 ms |       79 |
 ---------------------------------------------------

Thanks,

	Ingo
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