Date: Mon, 19 Oct 2009 17:14:55 +0200 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-current@freebsd.org Subject: Re: softclock swis not bound to specific cpu Message-ID: <hbhvp3$9eg$1@ger.gmane.org> In-Reply-To: <alpine.BSF.2.00.0910191604250.48055@fledge.watson.org> References: <20091018202407.656c3863.taku@tackymt.homeip.net> <alpine.BSF.2.00.0910191604250.48055@fledge.watson.org>
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Robert Watson wrote: > > On Sun, 18 Oct 2009, Taku YAMAMOTO wrote: > >> I noticed that the softclock threads didn't seem to be bound to any cpu. >> >> I'm not sure whether it's the Right Thing (TM) to bind them to the >> corresponding cpus though: it might be good to give the scheduler a >> chance to rebalance callouts. >> >> I'm about to test the modification like the attached diff. Comments >> are welcome. > > Yes, I think the intent is that they have a "soft" affinity to the CPU > where the lapic timer is firing, but not a hard binding, allowing them > to migrate if required. It would be interesting to measure how > effective that soft affinity is in practice under various loads -- > presumably the goal would be for the softclock thread to migrate if a > higher (lower) priority thread is hogging the CPU. So why are there NCPU softclock threads if the binding isn't important?
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