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    SubjectRe: [PATCH 1/5] ftrace: Synchronize variable setting with breakpoints
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    On Thu, 2012-05-31 at 16:37 -0400, Steven Rostedt wrote:
    > On Thu, 2012-05-31 at 22:26 +0200, Peter Zijlstra wrote:
    >
    > > Right, but when you loose stop-machine you could simply do 30k
    > > kmap_atomic/kunmap_atomic's consecutively since you're not holding
    > > anybody up.
    >
    > It requires 3 IPIs per update too. Thus that's 90,000 IPIs you are
    > blasting^Wsending to all CPUs.

    Uhm, no.

    for_each() {
    kmap_atomic()
    frob int3
    kunmap_atomic();
    }

    sync-ipi-broadcast();

    for_each() {
    kmap_atomic();
    frob tail
    kunmap_atomic();
    }

    sync-ipi-broadcast();

    for_each() {
    kmap_atomic();
    frob head
    kunmap_atomic();
    };

    sync-ipi-broadcast();

    How is that sending 90k ipis?


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