Re: threading question

From: <ognen@gene.pbi.nrc.ca>
To: Davide Libenzi <davidel@xmailserver.org>
Cc: <linux-kernel@vger.kernel.org>
Subject: Re: threading question
Date: Tue, 12 Jun 2001 15:48:34 -0600 (CST)	[thread overview]
Message-ID: <Pine.LNX.4.30.0106121546510.11222-100000@gene.pbi.nrc.ca> (raw)
In-Reply-To: <XFMail.20010612144449.davidel@xmailserver.org>

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