On Tue, Nov 29, 2016 at 02:46:14PM +0000, Liang, Kan wrote:
> > And note that we _ALWAYS_ set the IN bits, even for !sampling events.
> > Also note we set max_period to (1<<31) - 1, so we should never exceed 31
> > bits.
> >
>
> The max_period is 0xfffffffff.
>
> The limit is breaked by this patch.
> 069e0c3c4058 ("perf/x86/intel: Support full width counting")
> https://patchwork.kernel.org/patch/2784191/
>
> /* Support full width counters using alternative MSR range */
> if (x86_pmu.intel_cap.full_width_write) {
> x86_pmu.max_period = x86_pmu.cntval_mask;
> x86_pmu.perfctr = MSR_IA32_PMC0;
> pr_cont("full-width counters, ");
> }
>
Wth do KNL/SLM have full_width_write set if they have short counters? I
should the whole point of the full_wdith thing was that in that case the
counters were actually 64bit wide.
