Re: [PATCH 2/11] x86: convert to generic helpers for IPI function calls

[Nick Piggin <npiggin@suse.de>]

On Tue, Apr 22, 2008 at 06:22:17PM -0700, Linus Torvalds wrote:
> 
> 
> On Wed, 23 Apr 2008, Nick Piggin wrote:
> > 
> > The "too expensive to check the shared queue" is one aspect of it. The
> > shared queue need not have events *for us* (at least, unless Jens has
> > changed the implementation a bit) but it can still have events that we
> > would need to check through.
> > 
> > I don't think deadlock is a problem (any more than with multiple vectors).
> 
> I'm happy with it either way, but as pointed out by Ralf, for the MIPS 
> version of the patch there aren't even other vectors available.
 
Yep.

> So sharing the vector is going to be a requirement on other architectures, 
> maybe we should look at whether we can make it generic and peform well 
> regardless?

I don't think it will perform terribly _poorly_ by sharing the vector.
If you have a look at how serialised the old code is...

If there is a noticable slowdown anywhere, we could I suppose create a
2nd variant for small numbers of CPUs, or shared vector case, but I'd
say the existing code should be fine I think.