Messages in this thread | | | Subject | Re: [RFC PATCH 2/2] perf stat: Use event group to simulate PMI on PMI-less hardware counter | From | Lin Ming <> | Date | Wed, 10 Nov 2010 22:45:19 +0800 |
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On Wed, 2010-11-10 at 20:21 +0800, Peter Zijlstra wrote: > On Wed, 2010-11-10 at 14:15 +0800, Lin Ming wrote: > > Some hardware counters(for example, Intel RAPL) can't generate interrupt > > when overflow. So we need to simulate the interrupt to periodically > > record the counter values. Otherwise, the counter may overflow and the > > wrong value is read. > > > > This patch uses event group to simulate PMI as suggested by Peter > > Zijlstra, http://marc.info/?l=linux-kernel&m=128220854801819&w=2 > > > > create_group_counters() will create a group with 2 events, one hrtimer > > based event as the group leader, and the other event to count. The > > hrtimer is fired periodically, so the sibling event can record its > > counter value periodically as well. > > I'm terribly confused here.... > > - you introduce perf_event_attr:pmi_simulate, but then you never > implement it -- nor do we need it afaict.
Someone need to simluate pmi will use it in future.
> > > - you use grouped counters for perf-stat, perf-stat doesn't use > sampling so I don't see a need to group events to simulate the PMI. >
Aha, sorry, actually, I mean to periodically read the PMI-less counter and reset it to zero each time to avoid overflow.
Well, seems I have done this in the wrong way. Let me re-think about it.
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