Re: AVX support

[Martin Husemann <martin%duskware.de@localhost>]

On Mon, Aug 15, 2016 at 09:57:05AM +0200, Maxime Villard wrote:
> One huge problem that struck me was that the fpu state is placed in the 
> kernel
> stack, which means we lose ~2500 bytes of stack. With the latest MPX states 
> and
> the future extensions, we will lose even more memory. The priority is 
> moving the
> fpu out of the pcb. We could give a look at FreeBSD [3], since their pcb 
> only
> has a pointer to a dynamically-allocated area.

No need to look at FreeBSD for that ;-)

When I last measured that for sparc64, where we have only a pointer in the
pcb, I never saw any process exit that did NOT allocate the fpu state.

This was some years ago, and maybe my instrumentation was bogus.

If this is still the case, it might make more sense to just add another
page to the uarea instead and save the pool_cache_get() overhead.

Martin