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    SubjectRe: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling
    On Wed, Oct 21, 2015 at 02:19:49PM -0700, Alexei Starovoitov wrote:

    > >Urgh, that's still horridly inconsistent. Can we please come up with a
    > >consistent interface to perf?

    > My suggestion was to do ioctl(enable/disable) of events from userspace
    > after receiving notification from kernel via my bpf_perf_event_output()
    > helper.

    > Wangnan's argument was that display refresh happens often and it's fast,
    > so the time taken by user space to enable events on all cpus is too
    > slow and ioctl does ipi and disturbs other cpus even more.
    > So soft_disable done by the program to enable/disable particular events
    > on all cpus kinda makes sense.

    And this all makes me think I still have no clue what you're all trying
    to do here.

    Who cares about display updates and why. And why should there be an
    active userspace part to eBPF programs?


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