Messages in this thread | | | Date | Thu, 16 Apr 2015 17:43:57 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH V2 1/6] perf,core: allow invalid context events to be part of sw/hw groups |
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> Even if you ignore the fundamental semantics of groups, there are other > problems with allowing shared contexts: > > * The *_txn functions only get called on the group leader's PMU. If your > system PMU has these functions, they are not called. > > * Event rotation is per ctx, but now you could have some events in a CPU > PMU's context, and some in the uncore PMU's context. So those can race > with each other. > > * Throttling is also per-context. So those can race with each other too.
There's also a break down of behaviour: events in the uncore context will get migrated to another CPU in the event of a hot unplug, while events that are grouped with CPU events (and hence live in the CPU context) will be destroyed.
Mark.
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