Date: Sun, 26 Nov 2006 19:01:44 +0100 From: Ivan Voras <ivoras@fer.hr> To: freebsd-arch@freebsd.org Subject: Re: What is the PREEMPTION option good for? Message-ID: <ekckpt$4h6$1@sea.gmane.org> In-Reply-To: <20061126174041.V83346@fledge.watson.org> References: <20061119041421.I16763@delplex.bde.org> <ejnvfo$tv2$1@sea.gmane.org> <ek4gc8$492$1@sea.gmane.org> <20061126174041.V83346@fledge.watson.org>
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Robert Watson wrote: > There's a known performance regression with PREEMPTION and loopback > network traffic on UP or UP-like systems due to a poor series of context > switches occuring in the network stack. If your benchmark involves the > above web load over the loopback, that could be the source of what > you're seeing. If it's not loopback traffic, then that's not the source > of the problem. The dynamic stuff is accessing the database (fairly intensively) over the loopback. > You might try fiddling with kern.sched.ipiwakeup.enabled and see what > the effect is, btw -- this controls whether or not the scheduler wakes > up another idle CPU to run a thread when waking up that thread, rather > than queuing it to run which may occur on the other CPU at the next > clock tick. Try this with or without PREEMPTION?
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