Re: pthread_create() slow for many threads; also time to revisit64b context switch optimization?

[Ingo Molnar]

* Ulrich Drepper <drepper@xxxxxxxxx> wrote:

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> Jamie Lokier wrote:
> > Suggest:
> > 
> > +#define MAP_STACK       0x20000         /* 31bit or 64bit address for stack, */
> > +                                        /* whichever is faster on this CPU */
> 
> I agree.  Except for the comment.
> 
> 
> > Also, is this _only_ useful for thread stacks, or are there other
> > memory allocations where 31-bitness affects execution speed on old P4s?
> 
> Actually, I would define the flag as "do whatever is best assuming the
> allocation is used for stacks".
> 
> For instance, minimally the /proc/*/maps output could show "[user
> stack]" or something like this.  For security, perhaps, setting of
> PROC_EXEC can be prevented.

makes sense. Updated patch below. I've also added your Acked-by. Queued 
it up in tip/x86/urgent, for v2.6.27 merging.

( also, just to make sure: all Linux kernel versions will ignore such 
  extra flags, so you can just update glibc to use this flag 
  unconditionally, correct? )

	Ingo

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