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

[Ingo Molnar]

* Jamie Lokier <jamie@xxxxxxxxxxxxx> wrote:

> > how about this then?
> 
> > +#define MAP_64BIT_STACK 0x20000         /* give out 32bit addresses on old CPUs */
> 
> I think the flag makes sense but it's name is confusing - 64BIT for a 
> flag which means "maybe request 32-bit stack"!  Suggest:
> 
> +#define MAP_STACK       0x20000         /* 31bit or 64bit address for stack, */
> +                                        /* whichever is faster on this CPU */

ok. I've applied the patch below to tip/x86/urgent.

> Also, is this _only_ useful for thread stacks, or are there other 
> memory allocations where 31-bitness affects execution speed on old 
> P4s?

just about anything i guess - but since those CPUs do not really matter 
anymore in terms of bleeding-edge performance, what we care about is the 
intended current use of this flag: thread stacks.

	Ingo

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