Re: Hardware limits on numbers of threads?

[Jakub Jelinek <jakub@redhat.com>]

On Wed, Sep 18, 2002 at 09:37:58AM -0200, Denis Vlasenko wrote:
> On 18 September 2002 04:43, Dan Kegel wrote:
> > http://people.redhat.com/drepper/glibcthreads.html says:
> > > Hardware restrictions put hard limits on the number of
> > > threads the kernel can support for each process.
> > > Specifically this applies to IA-32 (and AMD x86_64) where the thread
> > > register is a segment register. The processor architecture
> > > puts an upper limit on the number of segment register values
> > > which can be used (8192 in this case).
> >
> > Is this true?  Where does the limit come from?
> 
> It is true that on x86 you have only 8192 different segment selectors
> at a time. Nobody says you can't modify segment descriptors on demand.
> 
> If I'm not mistaken, Linux kernel does precisely this. It has per-CPU
> allocated GDT entries, not per-task.

That page has been written way before set_thread_area(2) (and other kernel
threading changes) were written.

	Jakub