On Wed, Nov 21, 2018 at 12:14 AM Peter Zijlstra <pet...@infradead.org> wrote: > > On Tue, Nov 20, 2018 at 02:38:54PM -0800, Andi Kleen wrote: > > > In fact, I'll argue FREEZE_ON_OVERFLOW is unfixably broken for > > > independent counters, because while one counter overflows, we'll stall > > > counting on all others until we've handled the PMI. > > > > > > Even though the PMI might not be for them and they very much want/need > > > to continue counting. > > > > We stop all counters in any case for the PMI. With freeze-on-PMI it just > > happens slightly earlier. > > Hiding the PMI is fine and good. The PMI is not the workload. Stopping > it earlier is _NOT_ good, it hides your actual workload.
It does seem that FREEZE_PERFMON_ON_PMI (misnamed as it is) is of rather limited use (or even negative, in our case) to a counter that's already restricted to ring 3. - Kyle
