> On Wed, 20 Apr 2016, Liang, Kan wrote: > > > The stop of the box1 events disables the whole machinery on that > > > node and therefor the box0 event is wreckaged as well. Hmm? > > > > > Right. How about check the SKL_UNC_PERF_GLOBAL_CTL in enable_event? > > If it's cleared, we can reset it there. The drawback is that there > > will be an extra rdmsrl and a possible wrmsrl. > > Well, that does not buy anything as you cannot disable the thing at all, > unless > you have refcounting. And that refcounting needs to be in the 'type' > struct and that would probably be some real pain to implement. > > The question is whether we need enable/disable at all. If the type is > initialized we enable it and on exit we disable it. Ditto on cpu hotplug - > which > is also used for init to enable all nodes. > > So if there is no drawback in letting the thing enabled if no events are > armed, > then we really can do w/o the enable/disable_box callbacks. >
There is no drawback in letting the thing enabled, but PERF_GLOBAL_CTL could be disabled after Package C7. I add the enable/disable thing to try to workaround it. I once did the test on a SKL laptop. If the machine goes idle for a while, then the uncore counter will always return 0. For fixing it, we have to re-enable PERF_GLOBAL_CTL. I think I made a typo in previous reply. I mean we can check it or just force rewrite the PERF_GLOBAL_CTL in enable_box. We don't need disable_box since there is no drawback in letting the thing enabled. The HSW and BDW client also have similar errata. If it's OK for you, I will send another patch for them. Thanks, Kan
