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>>>>                   if (am) >>>>                           am->prev_msr = 0; >>>>           } >>> >>> Nope. If you want the value reported to the user to start over from zero, >>> then prev_msr should be set to the current value of the counter. That >>> would make the next read start from zero. >>> >> When an RMID is reallocated, the hardware detects the state >> transition and the first read returns "Unavailable". At that point, >> the counter is reset and begins counting again from 0. This is the >> expected behavior on AMD systems. Therefore, setting prev_msr to 0 >> is the correct behavior. > > I believe Tony was curious how this looks from the user's perspective. > >>>From what I understand it is neither of the presented options but instead: > > 3) Internal cache of hardware counter (prev_msr) is reset when resctrl discovers > that the underlying counter has been re-assigned. > There is a separate software maintained cumulative count to which the > hardware counter value is added as the event is tracked. This cumulative > count is the value returned to the user. > The user thus always sees that the event count increase and it is > guaranteed to only increase based on a portion of memory bandwidth > consumed by the RMID/event being tracked. > The returned (cumulative) count will not be accurate if the underlying > counter was re-assigned. The user does not have insight into how long the > underlying counter(s) was assigned to the event being counted. Agreed. When this happens, the counters will not be accurate. Thanks Babu