Messages in this thread | | | Date | Thu, 21 Apr 2016 10:03:18 +0200 (CEST) | From | Thomas Gleixner <> | Subject | RE: [PATCH 1/1] perf/x86/intel/uncore: Add support for Intel SKL client uncore |
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On Wed, 20 Apr 2016, Liang, Kan wrote: > > 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 don't see how that solves it. If a counter is active, then C7 will stop it and you wont get anything useful from it after returning from C7. Or does an active counter prevent C7?
> 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.
Hmm, but that does only help for new events after returning from C7, right?
> 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.
Sure, but then you can just unconditionally enable it. IOW, leave the enable callback as is.
Thanks,
tglx
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