Date: Thu, 02 May 2002 10:45:01 -0400 (EDT) From: John Baldwin <jhb@FreeBSD.org> To: Jonathan Mini <mini@FreeBSD.org> Cc: Andrew Gallatin <gallatin@cs.duke.edu>, freebsd-smp@FreeBSD.org Subject: Re: hlt when idle? Message-ID: <XFMail.20020502104501.jhb@FreeBSD.org> In-Reply-To: <20020502072949.C56560@stylus.haikugeek.com>
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On 02-May-2002 Jonathan Mini wrote: > John Baldwin [jhb@FreeBSD.org] wrote : > >> >> On 01-May-2002 Jonathan Mini wrote: >> > Andrew Gallatin [gallatin@cs.duke.edu] wrote : >> >> > No, the interrupts seem to be round-robin, but each clock intr is only >> >> > sent to one CPU unlike on alpha where they are broadcast. >> >> >> >> So each CPU gets (1/num_cpu) * hz clock interrupts/sec? >> > >> > Yes, but because the timer is set to num_cpu*hz, each CPU ends up getting >> > the normal hz interrupts. That's why it runs round-robin but looks like a >> > broadcast. >> >> Eh, are you talking about the Alpha? On x86 we don't do this and have to >> use >> IPI's to simulate a broadcast-type deal. >> > > I am obviously thinking about some other SMP implementation, but I have no > idea which one. Somebody, somewhere, sets the routing of the clock interrupt > to be delivered in a round-robin fashion, and then multiplies the clock > frequency by the number of processors. They're really proud of this solution, > because (they claim) it reduces contentions of clock-triggered events across > processors. It probably does. > Maybe it was Sun? Maybe? On the alpha it is very nice, because not only is it broadcast, but it's broadcast in a staggered fashion, so not all CPU's get the clock interrupt at the same time, thus reducing contention. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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