From owner-freebsd-smp Mon Apr 28 05:00:19 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.5/8.8.5) id FAA10579 for smp-outgoing; Mon, 28 Apr 1997 05:00:19 -0700 (PDT) Received: from cais.cais.com (root@cais.com [199.0.216.4]) by hub.freebsd.org (8.8.5/8.8.5) with ESMTP id FAA10574 for ; Mon, 28 Apr 1997 05:00:17 -0700 (PDT) Received: from earth.mat.net (root@earth.mat.net [205.252.122.1]) by cais.cais.com (8.8.5/8.7.3) with SMTP id IAA29046; Mon, 28 Apr 1997 08:00:16 -0400 (EDT) Received: from Journey2.mat.net (journey2.mat.net [205.252.122.116]) by earth.mat.net (8.6.12/8.6.12) with SMTP id IAA11041; Mon, 28 Apr 1997 08:00:14 -0400 Date: Mon, 28 Apr 1997 07:59:35 -0400 (EDT) From: Chuck Robey To: Ben Black cc: FreeBSD-SMP@FreeBSD.org Subject: Re: SMP In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-smp@FreeBSD.org X-Loop: FreeBSD.org Precedence: bulk On Mon, 28 Apr 1997, Ben Black wrote: > > > > I'm confused, then. If there's only one kernel, then only one cpu can > > run it, so only one cpu can field the system calls. If both cpu's can > > field system calls, then unless they contact the other one to get the > > work done, then there must be two copies of the kernel ruinning, right? > > > > I'm probably misunderstanding something. Maybe you meant only one piece > > of software called "kernel" but two cpus running it? > > > > hence my saying one kernel. there is a single kernel image in memory and > both CPUs execute different (or the same) parts of it at the same time. > the single lock is to keep the CPUs from stepping on each other. when > one CPU wants to access a shared resource (and pretty much everything in > the kernel is considered shared) then it acquires the mplock, does its > business, releases the lock and continues. if the other CPU has the lock > when one wants to acquire it, the second CPU waits. > > one kernel, one lock. Ahh, ok, I'm clear on that now. > > > b3n > > > ----------------------------+----------------------------------------------- Chuck Robey | Interests include any kind of voice or data chuckr@eng.umd.edu | communications topic, C programming, and Unix. 9120 Edmonston Ct #302 | Greenbelt, MD 20770 | I run Journey2 and picnic, both FreeBSD (301) 220-2114 | version 3.0 current -- and great FUN! ----------------------------+-----------------------------------------------