Re: [patch] voluntary-preempt-2.6.8-rc2-M5

Ingo Molnar
2004-08-02T09:28:04Z

* Lee Revell <rlrevell@joe-job.com> wrote:

> Can you post this patch, or add it to the voluntary preempt series?
> The one posted several weeks ago worked for me but had to be applied
> manually and has probably been improved since.
>
> Just to clarify the last numbers I posted were for O2.

i've uploaded the preempt-timing patch (relative to -O2):

http://redhat.com/~mingo/voluntary-preempt/preempt-timing-on-2.6.8-rc2-O2

QuickStart for those who havent used it yet: enable PREEMPT_TIMING in
.config and add preempt_thresh=1000 [== 1000 usec threshold] to the
kernel's boot options.

i changed the original patch to make it a bit more usable - the
threshold can be changed runtime via /proc/sys/kernel/preempt_thresh,
and the units are microseconds not milliseconds.

the timings should be pretty accurate in vp=0,1,2,3 modes as well.

Note that this patch only measures latencies of critical sections
(preempt-off sections), not other latencies that occur when running
!CONFIG_PREEMPT or with kernel_preemption=0.

Ingo