Re: Is it possible to make -lpthread program to use 100% CPU?

On Sun, 02 May 2004 00:37:53 -0400
"Daniel M. Eischen" <eischen_at_vigrid.com> wrote:

> Alexandre Sunny Kovalenko wrote:
> > On Sat, 1 May 2004 14:49:47 -0400 (EDT)
> > Daniel Eischen <eischen_at_vigrid.com> wrote:
> > 
> > 
> >>On Sat, 1 May 2004, Alexandre Sunny Kovalenko wrote:
> >>
> >>
> >>>On Thu, 29 Apr 2004 17:16:21 +0200
> >>>Ivan Voras <ivoras_at_fer.hr> wrote:
> >>>
> >>>
> >>>>Alexandre Sunny Kovalenko wrote:
> >>>>
> >>>>
> >>>>>Alternatively, if there is a need to test a patch or time a program 
> >>>>>in this environment, it could easily be accomplished -- it is a non-
> >>>>>production box.
> >>>>
> >>>>Could you turn off Hyperthreading and report any changes?
> >>>>
> >>>
> >>>I have updated my system to the latest CTM mailing on Friday (4/30) morning (EST).
> >>>This includes version 1.176 of kern_thread.c.
> >>>
> >>>I have turned off hyperthreading and got result, which muddles me rather -- try
> >>>as I might, with -lpthread I could not get past 50% CPU utilization (as reported 
> >>>by 'top') and  number of computations per second matching that (number is very 
> >>>close to that  for running single-threaded). Top report with thread view enabled
> >>>shows that both KSE are bound to CPU 0 (if I am interpreting C column properly).
> >>
> >>Are you using system or process scope threads?
> >>
> >>-- 
> >>Dan Eischen
> >
> > Sorry, should have mentioned that too. For -lthr PTHREAD_SCOPE_PROCESS is only 
> > available option. For -lpthread I have tried both, and results do not differ
> > much, which is what I expect on the machine that runs nothing else (unless
> > I do not understand PTHREAD_SCOPE_ option).
> 
> You need to use PTHREAD_SCOPE_SYSTEM in order to get another
> scheduling quantum (kse group) for each thread under libpthread.
> There's no way yet to tell the kernel which CPU should get
> each thread, so they may be scheduled on the same CPU.
> 
> What scheduler are you using?
> 
> -- 
> Dan Eischen
> 
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I did mention this one ;) With older sources (kern_thread.c 1.175) I have tried
both with the similar results. With the last update (last CTM from EST morning
on Friday 4/30) I only tried _ULE. If you need me to try _4BSD, let me know.

Just out of curiosity, if I have 64 threads and 4 CPUs would not result be the
same with PTHREAD_SCOPE_SYSTEM and PTHREAD_SCOPE_PROCESS, since I could not
get more KSEGs then I have CPUs, and default is 8 threads per KSEG? Or am I
totally off the mark?

-- 
Alexandre "Sunny" Kovalenko.