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

Ingo Molnar
2004-07-23T11:58:44Z

* Paolo Ciarrocchi <paolo.ciarrocchi@gmail.com> 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