From owner-freebsd-smp Thu Oct 23 17:15:01 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.7/8.8.7) id RAA08117 for smp-outgoing; Thu, 23 Oct 1997 17:15:01 -0700 (PDT) (envelope-from owner-freebsd-smp) Received: from dyson.iquest.net (dyson.iquest.net [198.70.144.127]) by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id RAA08096 for ; Thu, 23 Oct 1997 17:14:56 -0700 (PDT) (envelope-from toor@dyson.iquest.net) Received: (from root@localhost) by dyson.iquest.net (8.8.7/8.8.5) id TAA01451; Thu, 23 Oct 1997 19:14:48 -0500 (EST) From: "John S. Dyson" Message-Id: <199710240014.TAA01451@dyson.iquest.net> Subject: Re: SMP is slower when two processors are enabled In-Reply-To: <199710232354.TAA27809@steward.eecs.harvard.edu> from ShieYuan Wang at "Oct 23, 97 07:54:21 pm" To: shieyuan@eecs.harvard.edu (ShieYuan Wang) Date: Thu, 23 Oct 1997 19:14:48 -0500 (EST) Cc: freebsd-smp@freebsd.org X-Mailer: ELM [version 2.4ME+ PL31 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-smp@freebsd.org X-Loop: FreeBSD.org Precedence: bulk ShieYuan Wang said: > protocol stack to transfer unlimited data on the same local host. If I > only enable one processor, the throughput can be 35 MB/sec. However if > I enable the other processor hoping to get better throughput, I only get > 12 MB/sec. > > I know that locking overhead between multiple processors may be a lot. But > I never thought that it could be so high. Could anyone give me some clues > about this bad performance? My SMP 3.0 was installed about 6 months ago. > Does the more recent SMP have better performance and have solved the > performance problem? Your suggestion will be highly appriciated. > Most likely it is the overhead of moving data between CPUs. Could be cache effects also. -- John dyson@freebsd.org jdyson@nc.com