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    SubjectRe: [rfc][patch] x86-64 new smp_call_function design
    On Wed, Feb 27, 2008 at 02:04:18PM +0100, Andi Kleen wrote:
    > > On a 2 socket, 8 core system, I see anywhere up to nearly 16x better
    > > performance on a stress test. The common cases of call-all, and wait
    > > are improved the least, however I think that if call-single and nowait
    > > are turned into a high performance API, then new usages will pop up
    > > (eg. I started this because I wanted to do "call single, nowait" calls
    > > for migrating block IO completions back to submitting CPU; however I
    > > am also interested in improving the "call all, wait" case for example
    > > to improve vmalloc tlb flushing).
    > TLB flushing at least on x86-64 should be already well optimized on its
    > own. I would be surprised if you could do much better.

    *vmalloc* TLB flushing.

    void flush_tlb_all(void)
    on_each_cpu(do_flush_tlb_all, NULL, 1, 1);

    Of course we could use a new vector for it and speed it up a lot more,
    but after my vmalloc improvements I think that would be a waste of a
    vector at this point.

    > > As far as I understand, calling a subset of online CPUs that is not all or
    > > one, is used quite infrequently, so this might be OK.
    > With cpusets and isolation etc. it is the normal case.

    Oh really? Coming from what callers?

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