Date: Thu, 23 Oct 97 19:54:21 EDT From: ShieYuan Wang <shieyuan@eecs.harvard.edu> To: freebsd-smp@freebsd.org Subject: SMP is slower when two processors are enabled Message-ID: <199710232354.TAA27809@steward.eecs.harvard.edu>
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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
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