Date: Sat, 26 Mar 2005 15:54:06 -0800 From: John Pettitt <jpp@cloudview.com> To: "Paul A. Hoadley" <paulh@logicsquad.net> Cc: freebsd-questions@freebsd.org Subject: Re: hyper threading. Message-ID: <4245F61E.2000300@cloudview.com> In-Reply-To: <20050326232753.GA64620@grover.logicsquad.net> References: <c6ef380c050326061976f164b@mail.gmail.com> <1641928994.20050326192811@wanadoo.fr> <8C700529A2DFD74-A44-3A157@mblk-d34.sysops.aol.com> <439876144.20050326220638@wanadoo.fr> <8C7006AE7E80573-FAC-3B652@mblk-r28.sysops.aol.com> <49251524.20050326234521@wanadoo.fr> <20050326232753.GA64620@grover.logicsquad.net>
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Paul A. Hoadley wrote: >On Sat, Mar 26, 2005 at 11:45:21PM +0100, Anthony Atkielski wrote: > > > >>Where can I see the measurements? >> >> > >Here are some measurements. A few weeks ago I ran Unixbench 4.1.0 >(/usr/ports/benchmarks/unixbench) on a P4 2.8GHz with and without >hyperthreading enabled. I note a slight difference in the 10 minute >load average in favour of the uniprocessor run (0.00 vs 0.10 in the >hyperthreading run), though I doubt this alone could account for a 15% >difference in total score. > > >Uniprocessor run: >----------------- > BYTE UNIX Benchmarks (Version 4.1.0) > System -- bigbird.logicsquad.net > Start Benchmark Run: Sun Feb 20 08:23:08 CST 2005 > 14 interactive users. > 8:23AM up 3 days, 14:37, 14 users, load averages: 0.00, 0.00, 0.00 > [snip] > ========= > FINAL SCORE 270.4 > > >Hyperthreading run: >------------------- > BYTE UNIX Benchmarks (Version 4.1.0) > System -- bigbird.logicsquad.net > Start Benchmark Run: Sun Feb 20 17:22:33 CST 2005 > 2 interactive users. > 5:22PM up 2 mins, 2 users, load averages: 0.31, 0.23, 0.10 > [snip] > ========= > FINAL SCORE 228.9 > > Notice the HT run had load on the box (0.31) when it started. If you're going to run benchmarks you need to start with a clean reboot before each run and make sure all the background daemons have been killed and and the load is zero. However even then this is not a good test of HT - the point of HT is to improve throughput in multi thread workloads and the benchmark suite is basically single thread. What would be more interesting would be to run a test with a constant background load also running. In theory the HT should do a better job of balancing the load between the benchmark and the background than the BSD scheduler can on it's own. I don't have an HT box here or I'd try it but I'd love to know how it comes out if somebody is up for it. > > >
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