Re: Linux 2.6 context switching and posix threads performance question

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

On Sat, 2005-08-27 at 14:11 +0200, Mateusz Berezecki wrote:
> Hello List Readers,
> 
> I would really appreciate any comment on the overall performance of task
> switching with 25 000 threads running on the Linux system. I was asked to work
> on some software which spawns 25 000 threads and I am really worried if
> it will ever work on 2 CPU HP Blade. The kernel was modified to support
> bigger threads amount running (I have no idea how it was done, probably
> just changing hardcoded limits) What is the performance impact of
> so much threads on the overall system performance? Is there any ?
> Wouldn't it be that such application would spend all of its time
> switching contexts ? I'm asking for some kind of an authoritative answer
> quite urgently. What is the optimum thread amount on 2 CPU SMP system
> running Linux ?
> 
Well the obvious question is: what kernel version and which thread
library?

2.4 with LinuxThreads might have severe problems. However 2.6 with NPTL
should be able to handle it, IIRC Igno once did a million threads with
that combination just to show that it worked ;-).


-- 
Peter Zijlstra <a.p.zijlstra@chello.nl>