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    SubjectRe: [PATCH 1/3] perf: add context field to perf_event
    On 06/29/2011 07:08 PM, Frederic Weisbecker wrote:
    > On Wed, Jun 29, 2011 at 06:42:35PM +0300, Avi Kivity wrote:
    > > The perf_event overflow handler does not receive any caller-derived
    > > argument, so many callers need to resort to looking up the perf_event
    > > in their local data structure. This is ugly and doesn't scale if a
    > > single callback services many perf_events.
    > >
    > > Fix by adding a context parameter to perf_event_create_kernel_counter()
    > > (and derived hardware breakpoints APIs) and storing it in the perf_event.
    > > The field can be accessed from the callback as event->overflow_handler_context.
    > > All callers are updated.
    > >
    > > Signed-off-by: Avi Kivity<>
    > I believe it can micro-optimize ptrace through register_user_hw_breakpoint() because
    > we could store the index of the breakpoint that way, instead of iterating through 4 slots.

    Right, I noticed that while writing the patch.

    > Perhaps it can help in arm too, adding Will in Cc.
    > But for register_wide_hw_breakpoint, I'm not sure. kgdb is the main user, may be Jason
    > could find some use of it.

    I think an API should not require its users to iterate in their
    callbacks, even if it doesn't affect current users for some reason.

    error compiling committee.c: too many arguments to function

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