ULE vs. 4BSD in RELENG_7

Nick Evans nevans at talkpoint.com
Wed Oct 24 08:50:46 PDT 2007

On Wed, 24 Oct 2007 11:39:52 -0400
"Josh Carroll" <josh.carroll at gmail.com> wrote:

> > kern.sched.steal_thresh is/was one of the more effective tuning sysctls.
> > rev 1.205 of sched_ule had a change that was supposed to automatically
> > adjust it based on the number of cores. Is this the same 8 core system as
> > the other thread? In that case the commit dictates steal_thresh should be
> > set to 3. Give that a try.
> This is a quad core (single cpu) system. Do these values look proper then?
> kern.sched.steal_thresh: 2
> kern.sched.steal_idle: 1
> kern.sched.steal_htt: 1
> Thanks,
> Josh

Yes, that's the proper default. You could try setting steal_thresh to 1. I
noticed a problem with building ports on an 8 core Xeon system while 8
distributed.net crunchers were running. The port build would proceed
incredibly slowly, steal_thresh=1 helped a little bit. It might not make up
the 5% gap you're seeing though. During early ULE2/3 testing the other
variables Jeff recommended trying were sched.pick_pri (which I never saw
effect from), sched_tryself and sched.balance. They're all bools IIRC. Since
this workload is a bit different from any of mine it would be worthwhile to
try those variables.


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