Messages in this thread | | | Subject | Re: [tip:perf/urgent] perf/x86: Enable raw event access to Intel offcore events | From | Peter Zijlstra <> | Date | Mon, 21 Nov 2011 22:48:04 +0100 |
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On Mon, 2011-11-21 at 22:45 +0100, Stephane Eranian wrote: > On Mon, Nov 21, 2011 at 10:42 PM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: > > On Mon, 2011-11-21 at 22:39 +0100, Stephane Eranian wrote: > >> To solve this problem (in the general case), you need to know which > >> counter is taken (or required) > >> by ALL pinned system-wide events across all CPUs. Once you've > >> constructed the bitmap, you can > >> use it as the basis (used_mask) to try and schedule the group events. > >> > > Its worse, you also need to consider all task-pinned events if you want > > to be complete. That's an even worse problem. > > > But that you know because by the time you do the simulation you already > know the task the events are attached to. You can get to the list of events > already attached to the task. Again this is a best effort, it could well be > that someone else attaches pinned task events just after the simulation.
In the PAPI case yes, but what if you want to create a CPU-wide group, then you need to consider all task-pinned events that could possibly land on your CPU. Not fun.
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