Hyperthreading in P4

abhishek Sinha aby_sinha at yahoo.com
Mon Apr 29 12:56:06 EDT 2002


Hi

I am also using a dual Xeon 2.2 Ghz box and it seems
that the box is slower than my normal pentium 3 also.
The reason i guess is the kernel. If i watch my
/proc/interrupts i see all of them on the single CPU .
Upon research on the net i found that it required some
kind of IRQ routing patch , (ingo's i guess) so that
the CPU's perform better.

I havent had much exposure to writing Open MP programs
and then testing the power of the Xeon.

comments??

abhishek
--- "Ole W. Saastad" <ole at scali.no> wrote:
> 
> New Pentium 4 processors has hyper threading
> capabilities
> and when setting this the linux sees 4 cpus on each
> dual node.
> 
> I have done some testing with OpenMP programs and
> found that
> for OpenMP threaded programs there is no performance
> gain in using 
> the hypertheading. Using a number of threads that
> equal the number 
> of real processors seems to be optimal.
> However, this is the results from just a few OpenMP
> programs and
> might not tell a full story. 
> I would like comments from others who has played
> with threads 
> and hyperthreading in a Pentium 4 processor
> environment.
> 
> 
> Hyperthreading is claimed to perform better when
> running a large
> number of processes and a high number of threads.
> But this is most
> probably different applications or different
> requests lets say to a 
> web or db. server.
> 
> 
> -- 
> Ole W. Saastad, Dr.Scient. Scali AS P.O.Box 150
> Oppsal 0619 Oslo NORWAY 
> Tel:+47 22 62 89 68(dir) mailto:ole at scali.no
> http://www.scali.com 
> Are you meeting Petaflop requirements with Gigaflops
> performance ?
>     - Scali Terarack bringing Teraflops to the
> masses.
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=====
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