On Tue, Dec 19, 2017 at 11:07:09PM +0100, Peter Zijlstra wrote: > On Tue, Dec 19, 2017 at 03:08:58PM -0500, Liang, Kan wrote: > > > This all looks very wrong... In auto reload we should never call > > > intel_pmu_save_and_restore() in the first place I think. > > > > > > Things like x86_perf_event_update() and x86_perf_event_set_period() > > > simply _cannot_ do the right thing when we auto reload the counter. > > > > > > > I think it should be OK to call it in first place. > > For x86_perf_event_update(), the reload_times will tell if it's auto reload. > > Both period_left and event->count are carefully recalculated for auto > > reload. > > How does prev_count make sense when we've already reloaded a bunch of > times?
We can figure it out how often there was a reload based on the PEBS index. -Andi