On Tue, 5 Jun 2007, Jeff Roberson wrote:
On Wed, 6 Jun 2007, Bruce Evans wrote:
On Tue, 5 Jun 2007, John Baldwin wrote:
If this is the old #ifndef PREEMPTION manual preemption stuff, then just
remove it. I've been wanting to axe it for a while, rwlocks don't do the
manual preemption either, and if it is getting in the way it's best to
just
purge it.
Interesting, I've been wanting to do the opposite -- axe the #ifdef
PREEMPTION in a different place, in pagezero, since non-manual preemption
doesn't actually work for SCHED_4BSD (it works for SCHED_ULE, but last
time I checked, SCHED_ULE was 7% slower for my makeworld benchmark
since it lets CPUs go idle when there is a runnable process in the
hope of a better CPU to run on becoming available). My SMP kernel
that crashes has this ifdef removed. However, the crash doesn't
seem to be caused by pgzero.
You should try with kern.sched.pick_pri = 0. I have changed this to be the
default recently. This weakens the preemption and speeds up some workloads.
I haven't tried a new SCHED_ULE kernel yet.
Are you still experiencing a crash with -current sources?
It works now. Performance for compiling in parallel is down a little.
A bit over 2% relative to my best ever makeworld time which was with
a June 4 kernel. This seems to have something to do with the preemption
without PREEMPTION being too weak now.
Bruce
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