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<avi@xxxxxxxxxx> 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.
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