Re: [patch] voluntary-preempt-2.6.8-rc2-I3

[Ingo Molnar]

* Paolo Ciarrocchi <paolo.ciarrocchi@xxxxxxxxx> wrote:

> Hi Ingo,
> thanks for the clarification.
> 
> What about performance of vanilla vs voluntary-preempt-2.6.8-rc2-I3 ?
> Do you have numbers available ? Can we, somehow, support you ?

All known performance problems have been fixed in -I4. The focus is
mainly on latency. You can best support this patch by trying it out and
doing measurements - both latency and throughput measurements are
welcome. Latency measurement can be done via the latencytest tool:

  http://www.alsa-project.org/~iwai/latencytest-0.5.4.tar.gz

If you enable both CONFIG_PREEMPT_VOLUNTARY and CONFIG_PREEMPT then you
can use the /proc/sys/kernel/voluntary_preemption|kernel_preemption
sysctl knobs to turn the preemption features on/off. The following flag
combinations can be used to do comparisons:

 vanilla:                                             vp:0 kp:0
 CONFIG_PREEMPT:                                      vp:0 kp:1
 voluntary-preempt:                                   vp:1 kp:0
 voluntary-preempt + CONFIG_PREEMPT:                  vp:1 kp:1
 voluntary-preempt + softirq defer:                   vp:2 kp:0 [default]
 voluntary-preempt + softirq defer + CONFIG_PREEMPT:  vp:2 kp:1

each of the above combinations should work and should pretty exactly
represent that particular kernel (i.e. you can get vanilla
non-preemptible 2.6.8-rc2 kernel behavior by switching both flags on) -
but i typically use the default one for testing. 

	Ingo
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