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List:       openmosix-general
Subject:    [openMosix-general] Hyperthreading-aware schedulers
From:       Peter Cordes <peter () llama ! nslug ! ns ! ca>
Date:       2003-12-25 22:11:09
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I've never gotten around to doing benchmarks on HT systems (since we only
have a few Intel workstations; our clusters are AMD Opteron and Athlon), but
I saw this thread on linux-kernel:
http://www.ussg.iu.edu/hypermail/linux/kernel/0312.2/1293.html
It looks like what people are saying is that two tasks running on the same
physical CPU really do slow each other down a lot.  The total throughput
might still be greater than without HT.  If your cluster doesn't usually
have any idle CPUs, using HT might be a good thing.  This is especially true
if some of the programs you run have a small cache footprint and/or don't
create much memory traffic.  I would hazard a guess that cache contention is
one of the more serious problems with HT for number crunching.  (I'm usually
more inclined to make wild guesses than to run benchmarks... :)

 So, it looks like people are working on an SMT-aware scheduler.  If we're
lucky, it might make it into 2.6 sometime.

--=20
#define X(x,y) x##y
Peter Cordes ;  e-mail: X(peter@cor , des.ca)

"The gods confound the man who first found out how to distinguish the hours!
 Confound him, too, who in this place set up a sundial, to cut and hack
 my day so wretchedly into small pieces!" -- Plautus, 200 BC

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