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    SubjectRe: [PATCH] use per cpu data for single cpu ipi calls

    * Peter Zijlstra <peterz@infradead.org> wrote:

    > On Thu, 2009-01-29 at 12:13 +0100, Ingo Molnar wrote:
    > > * Peter Zijlstra <peterz@infradead.org> wrote:
    > >
    > > > > Can generic_smp_call_function_single_interrupt() ever see
    > > > > CSD_FLAG_ALLOC set now? If not, that kfree can go away.
    > > >
    > > > Like said above, removing that kmalloc will hurt people.
    > >
    > > the whole promise of generic-IPI seems to dwindle and we'll get back to
    > > roughly where we started out from.
    >
    > I'd not go that far, the per-cpu csd is a nice fallback, but removing
    > that kmalloc is just silly.
    >
    > And I see no reason why arch specific could do any better (aside from
    > sparc which has fancy ipis).

    well if the hw can embedd at least 64 bit of dataload in the IPI itself,
    we could get rid of a lot of complications. But since we cannot (on x86
    and most other architectures), we've got to demultiplex from generic data
    which brings up serialization issues and adds overhead .

    Ingo


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