Re: [PATCH 0 of 9] x86/smp function calls: convert x86 tlb flushes to use function calls [POST 2]

[Ingo Molnar <mingo@elte.hu>]

* Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> Ingo Molnar wrote:
> > nice stuff!
> >
> > I suspect the extra cost might be worth it for two reasons: 1) we could 
> > optimize the cross-call implementation further
> 
> Unfortunately, I think the kmalloc fix for the RCU issue is going to 
> hurt quite a lot.

yeah :-(

Nick, is there any way to get rid of that kmalloc() in the async 
function call case? The whole premise of the smp_function_call() rewrite 
was that it's faster - and now it's measurably slower.

At least we could/should perhaps standardize/generalize all the 
'specific' IPI handlers into the smp_function_call() framework: if 
function address equals to a pre-cooked IPI entry point we could call 
that function without a kmalloc. As these are all hardwired, 
__builtin_is_constant_p() could come to the help as well. Hm?

	Ingo