Messages in this thread | | | Date | Tue, 12 Jun 2001 13:07:11 -0600 (CST) | From | <> | Subject | Re: threading question |
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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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