Messages in this thread | | | Date | Mon, 12 Dec 2011 18:32:15 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 2/4] perf_event: add PERF_COUNT_HW_REF_CPU_CYCLES generic PMU event |
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* Peter Zijlstra <peterz@infradead.org> wrote:
> On Sun, 2011-12-11 at 00:28 +0100, Stephane Eranian wrote: > > This event counts the number of reference core cpu cycles. > > Reference means that the event increments at a constant rate which > > is not subject to core CPU frequency adjustments. The event may > > not count when the processor is in halted (low power) state. > > As such, it may not be equivalent to wall clock time. However, > > when the processor is not halted state, the event keeps > > a constant correlation with wall clock time. > > > > Signed-off-by: Stephane Eranian <eranian@google.com> > > --- > > include/linux/perf_event.h | 1 + > > 1 files changed, 1 insertions(+), 0 deletions(-) > > > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > > index 564769c..0885561 100644 > > --- a/include/linux/perf_event.h > > +++ b/include/linux/perf_event.h > > @@ -54,6 +54,7 @@ enum perf_hw_id { > > PERF_COUNT_HW_BUS_CYCLES = 6, > > PERF_COUNT_HW_STALLED_CYCLES_FRONTEND = 7, > > PERF_COUNT_HW_STALLED_CYCLES_BACKEND = 8, > > + PERF_COUNT_HW_REF_CPU_CYCLES = 9, > > > > PERF_COUNT_HW_MAX, /* non-ABI */ > > }; > > Does it make sense to add this to the 'generic' events? Are > other archs going to use this? > > That is, I already queued patch 1, I'm just wondering if the > generic bit makes sense, Even BUS_CYCLES seems to be a > questionable 'generic' event, but that's history and we can't > fix it.
If we named it in a generic way, with a generic, platform-independent meaning behind it, then it shouldn't be a problem. This is why i suggested naming it 'constant CPU cycles' - or 'constant freq cycles' or a variant of that.
Thanks,
Ingo
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