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    SubjectRe: [PATCH RFC v2 0/4] perf: IRQ-bound performance events
    On Sat, Jan 04, 2014 at 07:22:32PM +0100, Alexander Gordeev wrote:
    > Hello,
    >
    > This is version 2 of RFC "perf: IRQ-bound performance events". That is an
    > introduction of IRQ-bound performance events - ones that only count in a
    > context of a hardware interrupt handler. Ingo suggested to extend this
    > functionality to softirq and threaded handlers as well:

    Did you measure the overhead in workloads that do a lot of interrupts?
    I assume two WRMSR could be a significant part of the cost of small interrupts.

    For counting at least it would be likely a lot cheaper to just RDPMC
    and subtract manually.

    The cache miss example below is certainly misleading, as cache misses
    by interrupts are often a "debt", that is they are forced on whoever
    is interrupted. I don't think that is a good use of this.

    I guess it can be useful for cycles.

    -Andi


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