Re: [RESEND PATCH V3 2/8] perf/x86/intel: Basic support for metrics counters

[Liang, Kan]

On 8/28/2019 3:52 AM, Peter Zijlstra wrote:
> On Mon, Aug 26, 2019 at 07:47:34AM -0700, kan.liang@xxxxxxxxxxxxxxx wrote:
>
> > diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
> > index 81b005e4c7d9..54534ff00940 100644
> > --- a/arch/x86/events/core.c
> > +++ b/arch/x86/events/core.c
> > @@ -1033,18 +1033,30 @@ static inline void x86_assign_hw_event(struct perf_event *event,
> >   				struct cpu_hw_events *cpuc, int i)
> >   {
> >   	struct hw_perf_event *hwc = &event->hw;
> > +	int reg_idx;
> >   
> >   	hwc->idx = cpuc->assign[i];
> >   	hwc->last_cpu = smp_processor_id();
> >   	hwc->last_tag = ++cpuc->tags[i];
> >   
> > +	/*
> > +	 * Metrics counters use different indexes in the scheduler
> > +	 * versus the hardware.
> > +	 *
> > +	 * Map metrics to fixed counter 3 (which is the base count),
> > +	 * but the update event callback reads the extra metric register
> > +	 * and converts to the right metric.
> > +	 */
> > +	reg_idx = get_reg_idx(hwc->idx);
> > +
> >   	if (hwc->idx == INTEL_PMC_IDX_FIXED_BTS) {
> >   		hwc->config_base = 0;
> >   		hwc->event_base	= 0;
> >   	} else if (hwc->idx >= INTEL_PMC_IDX_FIXED) {
> >   		hwc->config_base = MSR_ARCH_PERFMON_FIXED_CTR_CTRL;
> > -		hwc->event_base = MSR_ARCH_PERFMON_FIXED_CTR0 + (hwc->idx - INTEL_PMC_IDX_FIXED);
> > -		hwc->event_base_rdpmc = (hwc->idx - INTEL_PMC_IDX_FIXED) | 1<<30;
> > +		hwc->event_base = MSR_ARCH_PERFMON_FIXED_CTR0 +
> > +				  (reg_idx - INTEL_PMC_IDX_FIXED);
> > +		hwc->event_base_rdpmc = (reg_idx - INTEL_PMC_IDX_FIXED) | 1<<30;
> >   	} else {
> >   		hwc->config_base = x86_pmu_config_addr(hwc->idx);
> >   		hwc->event_base  = x86_pmu_event_addr(hwc->idx);
>
> That reg_idx is a pointless unconditional branch; better to write it
> like:
>
> static inline void x86_assign_hw_event(struct perf_event *event,
> 				struct cpu_hw_events *cpuc, int i)
> {
> 	struct hw_perf_event *hwc = &event->hw;
> 	int idx;
>
> 	idx = hwc->idx = cpuc->assign[i];
> 	hwc->last_cpu = smp_processor_id();
> 	hwc->last_tag = ++cpuc->tags[i];
>
> 	switch (hwc->idx) {
> 	case INTEL_PMC_IDX_FIXED_BTS:
> 		hwc->config_base = 0;
> 		hwc->event_base	= 0;
> 		break;
>
> 	case INTEL_PMC_IDX_FIXED_METRIC_BASE ... INTEL_PMC_IDX_FIXED_METRIC_BASE+3:
> 		/* All METRIC events are mapped onto the fixed SLOTS counter */
> 		idx = INTEL_PMC_IDX_FIXED_SLOTS;
>
> 	case INTEL_PMC_IDX_FIXED ... INTEL_PMC_IDX_FIXED_METRIC_BASE-1:
> 		hwc->config_base = MSR_ARCH_PERFMON_FIXED_CTR_CTRL;
> 		hwc->event_base = MSR_ARCH_PERFMON_FIXED_CTR0 +
> 				  (idx - INTEL_PMC_IDX_FIXED);
> 		hwc->event_base_rdpmc = (idx - INTEL_PMC_IDX_FIXED) | 1<<30;
> 		break;
>
> 	default:
> 		hwc->config_base = x86_pmu_config_addr(hwc->idx);
> 		hwc->event_base = x86_pmu_event_addr(hwc->idx);
> 		hwc->event_base_rdpmc = x86_pmu_rdpmc_index(hwc->idx);
> 		break;
> 	}
> }
>
> On that; wth does this to the RDPMC userspace support!? Does that even
> work with these counters?

The event_base_rdpmc is only for kernel usage now.
But it seems we can update x86_pmu_event_idx() to use it as well.

Thanks,
Kan