On Thu, 2004-12-09 at 11:48 +0000, michael wrote: > Hi - I've had a quick look on the WWW but can't find much of help. I've > a dual Xeon box running testing and kernel from backports: > m@r:~$ uname -a > Linux r 2.4.27-1-686-smp #1 SMP Fri Sep 3 06:34:36 UTC 2004 i686 > GNU/Linux > > The SMP kernel does indeed make use of the processors available: 2 if > hyperthreading (HT) is off and 4 if it is on. > > My questions are: > a) for MPI codes (mpich v1.2.6 compiled with Intel 8.1 compilers), under > which circumstances is better performance achieved with HT on or off? > I'm looking for quite a detailed analysis which, if hasn't already been > done, I can kick off if anybody's interested > > b) for general day to day running do people leave HT on or turn it off? How threaded are your apps? Or, maybe, how many apps do you run at once? On Windows benchmarks, at least, performance of non-threaded apps drops when HT is turned on. -- ----------------------------------------------------------------- Ron Johnson, Jr. Jefferson, LA USA PGP Key ID 8834C06B I prefer encrypted mail. All of the "reporting" about Laci Peterson & Michael Jackson reminds me of the Don Henley song "Dirty Laundry": "Can we do the operation? Is the head dead yet? You know, the boys in the newsroom got a running bet. Get the widow on the set, we need dirty laundry."
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