Date: Wed, 5 Jul 2000 23:10:39 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: bright@wintelcom.net (Alfred Perlstein) Cc: grog@lemis.com (Greg Lehey), jeroen@vangelderen.org (Jeroen C. van Gelderen), eischen@vigrid.com (Daniel Eischen), jasone@canonware.com (Jason Evans), luoqi@watermarkgroup.com (Luoqi Chen), smp@FreeBSD.ORG Subject: Re: SMP meeting summary Message-ID: <200007052310.QAA27112@usr05.primenet.com> In-Reply-To: <20000703220823.Z25571@fw.wintelcom.net> from "Alfred Perlstein" at Jul 03, 2000 10:08:24 PM
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> The idea is that for spin or spin-then-sleep mutexes (very short > hold time) is that since you won't have as many processes as cpus > contending (and when you do it's ok) that the mutual exclusion is > so short lived that by the time the next 'thundering' process is > actually given the CPU, the likelyhood is that other processes have > already aquired _and_ released the spinlock making it more than > likely that the reasource is free. > > The idea is that the a quantum is actually so great that there's > little chance of one of the wake_all processes colliding on the > lock. This is a bogus idea, both in the case of a large number of processors, and in quantum ownership case. The quantum ownership case is "so long as I have work to do, if the scheduler gave me a quantum, it's my damn quantum!". In other words, the idea of voluntary preemption or semivoluntary preenption, such as one might get when the system makes a process blocke merely because it has made a system call that can't be immediately satisfied. A multithreaded of FSA process doesn't care about a single blocking context: it wants to use the remainder of its quantum. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the messagehelp
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