From: Kan Liang <kan.li...@linux.intel.com> With Icelake CPUs, the TopDown metrics are directly available as fixed counters and do not require generic counters, which make it possible to measure TopDown per thread/process instead of only per core.
The metrics and slots values have to be saved/restored during context switching. The saved values are also used as previous values to calculate the delta. The PERF_METRICS MSR value will be returned if RDPMC metrics events. Signed-off-by: Kan Liang <kan.li...@linux.intel.com> --- New for V2 arch/x86/events/core.c | 5 ++- arch/x86/events/intel/core.c | 101 +++++++++++++++++++++++++++++++++++-------- include/linux/perf_event.h | 3 ++ 3 files changed, 90 insertions(+), 19 deletions(-) diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index 6169af6bf723..fde44fdba256 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -2150,7 +2150,10 @@ static int x86_pmu_event_idx(struct perf_event *event) if (!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED)) return 0; - if (x86_pmu.num_counters_fixed && idx >= INTEL_PMC_IDX_FIXED) { + /* Return PERF_METRICS MSR value for metrics event */ + if (is_metric_idx(idx)) + idx = 1 << 29; + else if (x86_pmu.num_counters_fixed && idx >= INTEL_PMC_IDX_FIXED) { idx -= INTEL_PMC_IDX_FIXED; idx |= 1 << 30; } diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index 753a345a1db0..1c0dd95fd0d2 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -2254,6 +2254,11 @@ static int icl_set_topdown_event_period(struct perf_event *event) local64_set(&hwc->period_left, 0); } + if ((hwc->saved_slots) && is_first_topdown_event_in_group(event)) { + wrmsrl(MSR_CORE_PERF_FIXED_CTR3, hwc->saved_slots); + wrmsrl(MSR_PERF_METRICS, hwc->saved_metric); + } + perf_event_update_userpage(event); return 0; @@ -2272,7 +2277,7 @@ static u64 icl_get_metrics_event_value(u64 metric, u64 slots, int idx) return mul_u64_u32_div(slots, val, 0xff); } -static void __icl_update_topdown_event(struct perf_event *event, +static u64 icl_get_topdown_value(struct perf_event *event, u64 slots, u64 metrics) { int idx = event->hw.idx; @@ -2283,7 +2288,50 @@ static void __icl_update_topdown_event(struct perf_event *event, else delta = slots; - local64_add(delta, &event->count); + return delta; +} + +static void __icl_update_topdown_event(struct perf_event *event, + u64 slots, u64 metrics, + u64 last_slots, u64 last_metrics) +{ + u64 delta, last = 0; + + delta = icl_get_topdown_value(event, slots, metrics); + if (last_slots) + last = icl_get_topdown_value(event, last_slots, last_metrics); + + /* + * The 8bit integer percentage of metric may be not accurate, + * especially when the changes is very small. + * For example, if only a few bad_spec happens, the percentage + * may be reduced from 1% to 0%. If so, the bad_spec event value + * will be 0 which is definitely less than the last value. + * Avoid update event->count for this case. + */ + if (delta > last) { + delta -= last; + local64_add(delta, &event->count); + } +} + +static void update_saved_topdown_regs(struct perf_event *event, + u64 slots, u64 metrics) +{ + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); + struct perf_event *other; + int idx; + + event->hw.saved_slots = slots; + event->hw.saved_metric = metrics; + + for_each_set_bit(idx, cpuc->active_mask, INTEL_PMC_IDX_TD_BE_BOUND + 1) { + if (!is_topdown_idx(idx)) + continue; + other = cpuc->events[idx]; + other->hw.saved_slots = slots; + other->hw.saved_metric = metrics; + } } /* @@ -2295,6 +2343,7 @@ static u64 icl_update_topdown_event(struct perf_event *event) struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); struct perf_event *other; u64 slots, metrics; + bool reset = true; int idx; /* @@ -2316,26 +2365,45 @@ static u64 icl_update_topdown_event(struct perf_event *event) if (!is_topdown_idx(idx)) continue; other = cpuc->events[idx]; - __icl_update_topdown_event(other, slots, metrics); + __icl_update_topdown_event(other, slots, metrics, + event ? event->hw.saved_slots : 0, + event ? event->hw.saved_metric : 0); } /* * Check and update this event, which may have been cleared * in active_mask e.g. x86_pmu_stop() */ - if (event && !test_bit(event->hw.idx, cpuc->active_mask)) - __icl_update_topdown_event(event, slots, metrics); + if (event && !test_bit(event->hw.idx, cpuc->active_mask)) { + __icl_update_topdown_event(event, slots, metrics, + event->hw.saved_slots, + event->hw.saved_metric); - /* - * To avoid the known issues as below, the PERF_METRICS and - * Fixed counter 3 are reset for each read. - * - The 8bit metrics ratio values lose precision when the - * measurement period gets longer. - * - The PERF_METRICS may report wrong value if its delta was - * less than 1/255 of Fixed counter 3. - */ - wrmsrl(MSR_PERF_METRICS, 0); - wrmsrl(MSR_CORE_PERF_FIXED_CTR3, 0); + /* + * In x86_pmu_stop(), the event is cleared in active_mask first, + * then drain the delta, which indicates context switch for + * counting. + * Save metric and slots for context switch. + * Don't need to reset the PERF_METRICS and Fixed counter 3. + * Because the values will be restored in next schedule in. + */ + update_saved_topdown_regs(event, slots, metrics); + reset = false; + } + + if (reset) { + /* + * To avoid the known issues as below, the PERF_METRICS and + * Fixed counter 3 are reset for each read. + * - The 8bit metrics ratio values lose precision when the + * measurement period gets longer. + * - The PERF_METRICS may report wrong value if its delta was + * less than 1/255 of Fixed counter 3. + */ + wrmsrl(MSR_PERF_METRICS, 0); + wrmsrl(MSR_CORE_PERF_FIXED_CTR3, 0); + update_saved_topdown_regs(event, 0, 0); + } return slots; } @@ -3517,9 +3585,6 @@ static int intel_pmu_hw_config(struct perf_event *event) event->attr.config1 = event->hw.config & X86_ALL_EVENT_FLAGS; event->hw.flags |= PERF_X86_EVENT_TOPDOWN; - - if (is_metric_event(event)) - event->hw.flags &= ~PERF_X86_EVENT_RDPMC_ALLOWED; } } diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 3dc01cf98e16..afd53e46d5e6 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -133,6 +133,9 @@ struct hw_perf_event { struct hw_perf_event_extra extra_reg; struct hw_perf_event_extra branch_reg; + + u64 saved_slots; + u64 saved_metric; }; struct { /* software */ struct hrtimer hrtimer; -- 2.14.5