Date: Fri, 25 Apr 2003 15:04:02 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: jeev <jeev@boldinternet.net> Cc: freebsd-smp@freebsd.org Subject: Re: Dual 2.40ghz xeon w/hyperthreading Message-ID: <3EA9B0D2.2B3BA91C@mindspring.com> References: <000301c30afa$3dbd3e20$0200a8c0@mainframe>
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jeev wrote: > Basically guys, this box is not exceeding an ide computer I have on idea. > > I noticed the dual xeon to be slow. So I ran: > > dd if=/dev/urandom of=/dev/null bs=1m count=1024 > > on 2 servers, 1 is the top one and 1 is the xeon. > Obviously the ide killed the scsi with dual cpu's running hyperthreading, > why? SCSI vs. IDE is irrellevent for this test. Actually, I'd say use /dev/zero instead of /dev/urandom, and try it again. FWIW, hyperthreading isn't terrifically valuable without some compiler support; same for the Pentium 4. You probably want to turn hyperthreading off, or set up some form of SMT core negaffinity in your scheduler (the FreeBSD scheduler does not have specific knowledge of hyperthreading, so it can cause contention between different SMT cores in the same CPU, which can contribute to poor performance). -- Terry
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