[M3devel] userthreads vs. pthreads performance?

[Jay K]

O(1) scheduling is not a new idea. Just look at NT and probably Solaris and probably all the other non-free systems (AIX, Irix, HP-UX, Tru64, VMS, etc.)

Getting thread locals should not require a kernel call. It doesn't on NT. We can optimize this somewhat on most systems with __thread. I had that in briefly.

Entering an uncontended pthread mutex should not be expensive -- at least no kernel call, but granted a call and atomic op. Two calls because of the C layer.
But user threads pay for a call too of course.

Maybe I should profile some of this..

 - Jay

> From: dragisha at m3w.org
> To: mika at async.async.caltech.edu
> Date: Sun, 28 Mar 2010 21:14:57 +0200
> CC: m3devel at elegosoft.com
> Subject: Re: [M3devel] userthreads vs. pthreads performance?
> 
> I remember reading (long time ago) about how these (FUTEXes) are
> efficient in LINUX... Can I have your test code to try?
> 
> On Sun, 2010-03-28 at 12:11 -0700, Mika Nystrom wrote:
> > Well I have run programs on PPC_DARWIN and FreeBSD<X> and seen these sorts of things...
> > 
> > =?UTF-8?Q?Dragi=C5=A1a_Duri=C4=87?= writes:
> > >Which platform?
> > >
> > >On Sun, 2010-03-28 at 11:57 -0700, Mika Nystrom wrote:
> > >> Yep, sounds right.  
> > >> 
> > >> I was profiling some other thread-using code that slowed down
> > >> enormously
> > >> because of pthreads and it turned out the program was spending ~95%
> > >> of its time in accessing the thread locals via one of the pthread_
> > >> functions.
> > >> (The overhead of entering the kernel.)
> > >-- 
> > >Dragiša Durić <dragisha at m3w.org>
> -- 
> Dragiša Durić <dragisha at m3w.org>
> 
 		 	   		  
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://m3lists.elegosoft.com/pipermail/m3devel/attachments/20100328/77b70ea6/attachment-0002.html>