Date: Sun, 27 Apr 1997 23:58:37 -0400 (EDT) From: Chuck Robey <chuckr@mat.net> To: Ben Black <black@zen.cypher.net> Cc: FreeBSD-SMP@FreeBSD.org Subject: Re: SMP Message-ID: <Pine.BSF.3.91.970427235620.22821K-100000@Journey2.mat.net> In-Reply-To: <Pine.LNX.3.91.970427234820.32065N-100000@zen.cypher.net>
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On Sun, 27 Apr 1997, Ben Black wrote: > On Sun, 27 Apr 1997, Chuck Robey wrote: > > > On Sun, 27 Apr 1997, Ben Black wrote: > > > > > freebsd-smp is not the best example of how to do SMP. it uses the > > > simplest method: one giant kernel lock. i don't know that it is > > > particularly representative of advanced SMP operating systems (though > > > linux also uses a giant kernel lock). > > > > One per CPU? One lock total? How many copies of the kernel are running > one lock. one kernel. > > > at once? How is caching handled, per cpu, or globally (forcing the two > > cpu's to look like one?) When a system call executes, what handles it, > > one cpu? > > caching is handled in hardware with software awareness. system calls are > handled by whichever CPU gets scheduled for it.. hence, symmetric. 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? > > > 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! ----------------------------+-----------------------------------------------
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