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Date: Tue, 12 Jun 2001 12:15:01 -0700 (PDT)
From: Kip Macy <kmacy@netapp.com>
To: ognen@gene.pbi.nrc.ca
cc: linux-kernel@vger.kernel.org
Subject: Re: threading question
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For heavy threading, try a user-level threads package.

		-Kip


On Tue, 12 Jun 2001 ognen@gene.pbi.nrc.ca wrote:

> Hello,
> 
> due to the nature of the problem (a pairwise mutual alignment of n
> sequences results in mx. n^2 alignments which can each be done in a
> separate thread), I need to create and destroy the threads frequently.
> 
> I am not really comfortable with 1.4 - 1.5 speedups since the solution was
> intended as a Linux one primarily and it just happenned that it works (and
> now even better) on Solaris/SGI/OSF...
> 
> Best regards,
> Ognen
> 
> On Tue, 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?
> >
> > The code for creating threads is _horribly_ slow in Linuxthreads due
> > to the way it is implemented.
> >
> > > It is the
> > > same multi-threaded code, I am not using any tricks, the code basically
> > > uses PTHREAD_CREATE_DETACHED and PTHREAD_SCOPE_SYSTEM and the thread stack
> > > size is set to 8K (but the numbers are the same with larger/smaller stack
> > > sizes).
> > >
> > > Is there anything I am missing? Is this to be expected due to Linux way of
> > > handling threads (clone call)? I am just trying to explain the numbers and
> > > nothing else comes to mind....
> >
> > Linuxthreads is a rather bad pthreads implementation performance-wise,
> > mostly due to the rather different linux-native threading model.
> >
> > 	Christoph
> 
> -
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