From owner-freebsd-smp Thu May 2 7:47:11 2002 Delivered-To: freebsd-smp@freebsd.org Received: from mail.speakeasy.net (mail14.speakeasy.net [216.254.0.214]) by hub.freebsd.org (Postfix) with ESMTP id 6E90B37B428 for ; Thu, 2 May 2002 07:46:12 -0700 (PDT) Received: (qmail 8335 invoked from network); 2 May 2002 14:46:08 -0000 Received: from unknown (HELO server.baldwin.cx) ([216.27.160.63]) (envelope-sender ) by mail14.speakeasy.net (qmail-ldap-1.03) with DES-CBC3-SHA encrypted SMTP for ; 2 May 2002 14:46:08 -0000 Received: from laptop.baldwin.cx (gw1.twc.weather.com [216.133.140.1]) by server.baldwin.cx (8.11.6/8.11.6) with ESMTP id g42Ek0F07738; Thu, 2 May 2002 10:46:00 -0400 (EDT) (envelope-from jhb@FreeBSD.org) Message-ID: X-Mailer: XFMail 1.5.2 on FreeBSD X-Priority: 3 (Normal) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: <20020502072949.C56560@stylus.haikugeek.com> Date: Thu, 02 May 2002 10:45:01 -0400 (EDT) From: John Baldwin To: Jonathan Mini Subject: Re: hlt when idle? Cc: Andrew Gallatin , freebsd-smp@FreeBSD.org Sender: owner-freebsd-smp@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org 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 <>< 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