Date: Wed, 6 Jun 2007 16:28:01 +1000 (EST) From: Bruce Evans <brde@optusnet.com.au> To: Jeff Roberson <jroberson@chesapeake.net> Cc: src-committers@freebsd.org, John Baldwin <jhb@freebsd.org>, cvs-src@freebsd.org, cvs-all@freebsd.org, Attilio Rao <attilio@freebsd.org>, Bruce Evans <brde@optusnet.com.au>, Kostik Belousov <kostikbel@gmail.com> Subject: Re: cvs commit: src/sys/kern kern_mutex.c Message-ID: <20070606154548.F3105@besplex.bde.org> In-Reply-To: <20070605195839.I606@10.0.0.1> References: <200706051420.l55EKEih018925@repoman.freebsd.org> <3bbf2fe10706050829o2d756a4cu22f98cf11c01f5e4@mail.gmail.com> <3bbf2fe10706050843x5aaafaafy284e339791bcfe42@mail.gmail.com> <200706051230.21242.jhb@freebsd.org> <20070606094354.E51708@delplex.bde.org> <20070605195839.I606@10.0.0.1>
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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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