Messages in this thread | | | Subject | Re: [PATCH] perf: Store active software events in a hashlist | From | Peter Zijlstra <> | Date | Tue, 06 Apr 2010 17:27:33 +0200 |
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On Mon, 2010-04-05 at 16:08 +0200, Frederic Weisbecker wrote: > Each time a software event triggers, we need to walk through > the entire list of events from the current cpu and task contexts > to retrieve a running perf event that matches. > We also need to check a matching perf event is actually counting. > > This walk is wasteful and makes the event fast path scaling > down with a growing number of events running on the same > contexts. > > To solve this, we store the running perf events in a hashlist to > get an immediate access to them against their type:event_id when > they trigger.
So we have a hash-table per-cpu, each event takes a ref on the hash table, when the thing is empty we free it.
When the event->cpu == -1 (all cpus) we take a ref on all possible cpu's hash-table (should be online I figure, but that requires adding a hotplug handler).
Then on event enable/disable we actually add the event to the hash-table belonging to the cpu the event/task gets scheduled on, since each event can only ever be active on one cpu.
Right?
So looks good, altough I think we want to do that online/hotplug thing.
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