ULE vs. 4BSD in RELENG_7

[Nick Evans]

On Wed, 24 Oct 2007 09:39:29 -0400
"Josh Carroll" <josh.carroll at gmail.com> wrote:

> > 5-6% is a lot.  ULE has some tuning for makeworld in -current, which
> > for me reduced it to less than 1% slower than 4BSD (down from 5-10%
> > slower), for the case of makeworld -j4 over nfs on a 2-CPU system with
> > the sources pre-cached on the server and objects on a local file system,
> > and extensive local tuning of makeworld, nfs and network drivers.  I
> > think the tuning in ULE was mainly for a 2-CPU system, because makeworld
> > seemed to be very bad under ULE only with 2 CPUs.  Apparently, it is also
> > very bad with more CPUs.  There are sysctls to modify the ULE tuning.
> 
> I found Kris' document here:
> 
> http://people.freebsd.org/~kris/scaling/mysql.html
> 
> Which also mentions some ULE tuning. The sched_ule man page doesn't
> mention what these are. Can someone point me to a document that
> explains the sysctl tuning I can try?
> 
> I imagine I would want to tweak one or more of these:
> 
> kern.sched.preemption: 1
> kern.sched.topology: 0
> kern.sched.steal_thresh: 2
> kern.sched.steal_idle: 1
> kern.sched.steal_htt: 1
> kern.sched.balance_interval: 133
> kern.sched.balance: 1
> kern.sched.tryself: 1
> kern.sched.affinity: 3
> kern.sched.pick_pri: 1
> kern.sched.preempt_thresh: 64
> kern.sched.interact: 30
> kern.sched.slice: 13
> 
> But I'm not sure which to try. I did try setting kern.sched.pick_pri
> to 0, but that hasn't helped the ffmpeg workload at least.
> 
> Thanks,
> Josh
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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.

Nick