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Date: Fri, 25 Apr 2003 15:04:02 -0700
From: Terry Lambert <tlambert2@mindspring.com>
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To: jeev <jeev@boldinternet.net>
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Subject: Re: Dual 2.40ghz xeon w/hyperthreading
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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