Hi, On Thu, Nov 10, 2016 at 09:33:55AM +0100, Peter Zijlstra wrote: > Yes this is a problem, but no this cannot be done. We can't have per-cpu > storage per task. That rapidly explodes. > > Mark is looking at replacing this stuff with an rb-tree for big-little, > that would also allow improving this I think.
Unfortunately I've not had the chance to look at that since returning from Plumbers. Also, I was leaning towards the alternative approach we discussed, with a perf_event_task_contexts container, as that also solved some other issues with the way we used perf_event_context::pmu in big.LITTLE systems. Looking at the way perf_iterate_ctx is used, it seems that we're just trying to iterate over the active events for a context (i.e. those programmed into the HW at this point in time). Though I'm missing some subtlety, since we check event->state < PERF_EVENT_STATE_INACTIVE. We have a similar issue with perf_event_task_tick() needing to know the relevant contexts, and for that we have the active_ctx_list. Can't we do something similar and add an active_events_list to perf_event_context? Thanks, Mark.
