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    SubjectRe: [ofa-general] Re: [GIT PULL] please pull ummunotify

    > Anton Blanchard suggested a while back that this might be integrated
    > with perf-counters, since perf-counters already does mmap() tracking and
    > also provides events through an mmap()'ed buffer.
    > Has anybody looked into this?

    I didn't see the original suggestion. Certainly hooking in to existing
    infrastructure for user/kernel communication would be good.

    The fit doesn't seem great to me, although I am rather naive about perf
    counters. The problem that ummunotify is trying to solve is to let an
    app say 'for these 1000 address ranges (that possibly only cover a small
    part of my total address space), please let me know when the mappings
    are invalidated for any reason'.

    So getting those events in the kernel is no problem -- we have the MMU
    notifier hooks that tell us exactly what we need to know. The issue is
    purely the way userspace registers interest in address ranges, and how
    to kernel returns the events.

    For perf counters it seems that one would have to create a new counter
    for each address range... is that correct? And also I don't know if
    perf counter has an analog for the fast path optimization that
    ummunotify provides via a mmap'ed generation counter (a quick way for
    userspace to see 'nothing happened since last time you checked').

    - R.

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      Last update: 2009-09-17 16:27    [W:0.022 / U:99.708 seconds]
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