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

* 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


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