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SubjectRe: [PATCH 3/9] perf/x86/intel: Support overflows on SLOTS
On Tue, May 21, 2019 at 02:40:49PM -0700, kan.liang@linux.intel.com wrote:
> From: Andi Kleen <ak@linux.intel.com>
>
> The internal counters used for the metrics can overflow. If this happens
> an overflow is triggered on the SLOTS fixed counter. Add special code
> that resets all the slave metric counters in this case.

The SDM also talked about a OVF_PERF_METRICS overflow bit. Which seems
to suggest something else.

> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
> ---
> arch/x86/events/intel/core.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> index 75ed91a36413..a66dc761f09d 100644
> --- a/arch/x86/events/intel/core.c
> +++ b/arch/x86/events/intel/core.c
> @@ -2279,12 +2279,35 @@ static void intel_pmu_add_event(struct perf_event *event)
> intel_pmu_lbr_add(event);
> }
>
> +/* When SLOTS overflowed update all the active topdown-* events */
> +static void intel_pmu_update_metrics(struct perf_event *event)
> +{
> + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> + int idx;
> + u64 slots_events;
> +
> + slots_events = *(u64 *)cpuc->enabled_events & INTEL_PMC_MSK_ANY_SLOTS;
> +
> + for_each_set_bit(idx, (unsigned long *)&slots_events, 64) {

for (idx = INTEL_PMC_IDX_TD_RETIRING;
idx <= INTEL_PMC_IDX_TD_BE_BOUND; idx++)

perhaps?

> + struct perf_event *ev = cpuc->events[idx];
> +
> + if (ev == event)
> + continue;
> + x86_perf_event_update(event);

if (ev != event)
x86_perf_event_update(event)
> + }
> +}
> +
> /*
> * Save and restart an expired event. Called by NMI contexts,
> * so it has to be careful about preempting normal event ops:
> */
> int intel_pmu_save_and_restart(struct perf_event *event)
> {
> + struct hw_perf_event *hwc = &event->hw;
> +
> + if (unlikely(hwc->reg_idx == INTEL_PMC_IDX_FIXED_SLOTS))
> + intel_pmu_update_metrics(event);
> +
> x86_perf_event_update(event);
> /*
> * For a checkpointed counter always reset back to 0. This
> --
> 2.14.5
>

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