On Mon, May 22, 2017 at 04:55:47PM +0000, Liang, Kan wrote: > > > > On Fri, May 19, 2017 at 10:06:21AM -0700, kan.li...@intel.com wrote: > > > diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index > > > 580b60f..e8b2326 100644 > > > --- a/arch/x86/events/core.c > > > +++ b/arch/x86/events/core.c > > > @@ -101,6 +101,10 @@ u64 x86_perf_event_update(struct perf_event > > *event) > > > delta = (new_raw_count << shift) - (prev_raw_count << shift); > > > delta >>= shift; > > > > > > + /* Correct the count number if applying ref_cycles replacement */ > > > + if (!is_sampling_event(event) && > > > + (hwc->flags & PERF_X86_EVENT_REF_CYCLES_REP)) > > > + delta *= x86_pmu.ref_cycles_factor; > > > > That condition seems wrong, why only correct for !sampling events? > > > > For sampling, it's either fixed freq mode or fixed period mode. > - In the fixed freq mode, we should do nothing, because the adaptive > frequency algorithm will handle it. > - In the fixed period mode, we have already adjusted the period in > ref_cycles_rep(). > Therefore, we should only handle !sampling events here.
How so? For sampling events the actual event count should also be accurate.
