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SubjectRe: threading question
Hello,

a good suggestion was given to me to actually create as many threads as
there are CPUs (or a bit more) and then keep them asking for work when
they are done. This should help it (and avoid the pthread_create,
pthread_exit). I will implement this and report my results if there is
interest.

Thank you all,
Ognen

On Tue, 12 Jun 2001, Davide Libenzi wrote:

>
> On 12-Jun-2001 Christoph Hellwig wrote:
> > In article <Pine.LNX.4.30.0106121213570.24593-100000@gene.pbi.nrc.ca> you
> > wrote:
> >> On dual-CPU machines the speedups are as follows: my version
> >> is 1.88 faster than the sequential one on IRIX, 1.81 times on Solaris,
> >> 1.8 times on OSF/1, 1.43 times on Linux 2.2.x and 1.52 times on Linux 2.4
> >> kernel. Why are the numbers on Linux machines so much lower?
> >
> > Does your measurement include the time needed to actually create the
> > threads or do you even frequently create and destroy threads?
>
> This is an extract of the most busy vmstat report running under his tool :
>
> 12 0 0 15508 40980 24880 355480 0 0 0 0 141 481 100 0 0
> 19 0 0 15508 40248 24880 355480 0 0 0 0 142 564 100 0 0
> 12 0 0 15508 40112 24880 355480 0 0 0 0 150 543 100 0 0
> 11 0 0 15508 41272 24880 355480 0 0 0 0 156 594 99 1 0
> 17 0 0 15508 40408 24880 355480 0 0 0 0 156 474 99 1 0
> 17 0 0 15508 39840 24880 355480 0 0 0 0 135 475 100 0 0
> 21 0 0 15508 39568 24880 355480 0 0 0 0 125 409 100 0 0
> 21 0 0 15508 39668 24880 355480 0 0 0 0 135 420 100 0 0
> 16 0 0 15508 39760 24880 355480 0 0 0 0 149 486 100 0 0
>
>
> The context switch is very low and the user CPU utilization is 100% , I don't
> think it's system responsibility here ( clearly a CPU bound program ).
> Even if the runqueue is long, the context switch is low.
> I've just close to me a dual PIII 1GHz workstation that run an MTA that uses
> linux pthreads with context switching ranging between 5000 and 11000 with a
> thread creation rate of about 300 thread/sec ( relaying 600000 msg/hour ).
> No problem at all with the system even if the load avg is a bit high
> ( about 8 ).

--
Ognen Duzlevski
Plant Biotechnology Institute
National Research Council of Canada
Bioinformatics team

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