Messages in this thread | | | Date | Fri, 22 Mar 2013 18:36:40 +0100 | Subject | Re: [PATCH v5 0/2] perf: use hrtimer for event multiplexing | From | Stephane Eranian <> |
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On Fri, Mar 22, 2013 at 6:33 PM, Andi Kleen <ak@linux.intel.com> wrote: > > On Fri, Mar 22, 2013 at 11:51:37AM +0100, Stephane Eranian wrote: > > The current scheme of using the timer tick was fine > > for per-thread events. However, it was causing > > bias issues in system-wide mode (including for > > uncore PMUs). Event groups would not get their > > fair share of runtime on the PMU. With tickless > > kernels, if a core is idle there is no timer tick, > > and thus no event rotation (multiplexing). However, > > there are events (especially uncore events) which do > > count even though cores are asleep. > > Would it be possible to only do this when uncore events > are active? Otherwise it may have a large power cost > and actually change results, as the core counters > will tick more. > the hrtimer is activated only when multiplexing is needed and that's for any PMU.
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