From owner-freebsd-questions Fri Oct 17 19:51:25 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.7/8.8.7) id TAA24042 for questions-outgoing; Fri, 17 Oct 1997 19:51:25 -0700 (PDT) (envelope-from owner-freebsd-questions) Received: from wally.eecs.harvard.edu (wally.eecs.harvard.edu [140.247.60.30]) by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id TAA24037 for ; Fri, 17 Oct 1997 19:51:21 -0700 (PDT) (envelope-from shieyuan@eecs.harvard.edu) Received: from steward.eecs.harvard.edu (shieyuan@steward.eecs.harvard.edu [140.247.60.20]) by wally.eecs.harvard.edu (8.8.6/8.8.6) with ESMTP id WAA12691 for ; Fri, 17 Oct 1997 22:51:20 -0400 (EDT) From: ShieYuan Wang Received: (from shieyuan@localhost) by steward.eecs.harvard.edu (8.8.5/8.8.5) id WAA06872 for freebsd-questions@FreeBSD.ORG; Fri, 17 Oct 1997 22:51:14 -0400 (EDT) Message-Id: <199710180251.WAA06872@steward.eecs.harvard.edu> Subject: SMP is slower when two processors are enabled To: freebsd-questions@FreeBSD.ORG Date: Fri, 17 Oct 97 22:51:14 EDT Mailer: Elm [revision: 70.85] Sender: owner-freebsd-questions@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk Hi, I am using SMP 3.0 with a two Pentium-Pro motherboard. I found that SMP does not give me speedup at all when I enable two processors at the same time. My system even becomes only 1/3 of its throughput when there is only one processor enabled. I am uisng "stcp" and "rtcp" to test how fast my system can use TCP/IP 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. Shie-Yuan Wang CS Ph.D. student. Harvard University