From: Sandipan Das Date: Fri, 18 Apr 2025 03:43:01 +0000 (+0530) Subject: perf/x86/amd/uncore: Use hrtimer for handling overflows X-Git-Tag: v6.16-rc1~196^2~32 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6d937e044bc9bfd52dc50f7fc06d22018841472e;p=thirdparty%2Fkernel%2Flinux.git perf/x86/amd/uncore: Use hrtimer for handling overflows Uncore counters do not provide mechanisms like interrupts to report overflows and the accumulated user-visible count is incorrect if there is more than one overflow between two successive read requests for the same event because the value of prev_count goes out-of-date for calculating the correct delta. To avoid this, start a hrtimer to periodically initiate a pmu->read() of the active counters for keeping prev_count up-to-date. It should be noted that the hrtimer duration should be lesser than the shortest time it takes for a counter to overflow for this approach to be effective. Signed-off-by: Sandipan Das Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra Link: https://lore.kernel.org/r/8ecf5fe20452da1cd19cf3ff4954d3e7c5137468.1744906694.git.sandipan.das@amd.com --- diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c index 010024f09f2c4..e09bfbb4a4cdf 100644 --- a/arch/x86/events/amd/uncore.c +++ b/arch/x86/events/amd/uncore.c @@ -21,6 +21,7 @@ #define NUM_COUNTERS_NB 4 #define NUM_COUNTERS_L2 4 #define NUM_COUNTERS_L3 6 +#define NUM_COUNTERS_MAX 64 #define RDPMC_BASE_NB 6 #define RDPMC_BASE_LLC 10 @@ -38,6 +39,10 @@ struct amd_uncore_ctx { int refcnt; int cpu; struct perf_event **events; + unsigned long active_mask[BITS_TO_LONGS(NUM_COUNTERS_MAX)]; + int nr_active; + struct hrtimer hrtimer; + u64 hrtimer_duration; }; struct amd_uncore_pmu { @@ -87,6 +92,42 @@ static struct amd_uncore_pmu *event_to_amd_uncore_pmu(struct perf_event *event) return container_of(event->pmu, struct amd_uncore_pmu, pmu); } +static enum hrtimer_restart amd_uncore_hrtimer(struct hrtimer *hrtimer) +{ + struct amd_uncore_ctx *ctx; + struct perf_event *event; + int bit; + + ctx = container_of(hrtimer, struct amd_uncore_ctx, hrtimer); + + if (!ctx->nr_active || ctx->cpu != smp_processor_id()) + return HRTIMER_NORESTART; + + for_each_set_bit(bit, ctx->active_mask, NUM_COUNTERS_MAX) { + event = ctx->events[bit]; + event->pmu->read(event); + } + + hrtimer_forward_now(hrtimer, ns_to_ktime(ctx->hrtimer_duration)); + return HRTIMER_RESTART; +} + +static void amd_uncore_start_hrtimer(struct amd_uncore_ctx *ctx) +{ + hrtimer_start(&ctx->hrtimer, ns_to_ktime(ctx->hrtimer_duration), + HRTIMER_MODE_REL_PINNED_HARD); +} + +static void amd_uncore_cancel_hrtimer(struct amd_uncore_ctx *ctx) +{ + hrtimer_cancel(&ctx->hrtimer); +} + +static void amd_uncore_init_hrtimer(struct amd_uncore_ctx *ctx) +{ + hrtimer_setup(&ctx->hrtimer, amd_uncore_hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD); +} + static void amd_uncore_read(struct perf_event *event) { struct hw_perf_event *hwc = &event->hw; @@ -117,18 +158,26 @@ static void amd_uncore_read(struct perf_event *event) static void amd_uncore_start(struct perf_event *event, int flags) { + struct amd_uncore_pmu *pmu = event_to_amd_uncore_pmu(event); + struct amd_uncore_ctx *ctx = *per_cpu_ptr(pmu->ctx, event->cpu); struct hw_perf_event *hwc = &event->hw; + if (!ctx->nr_active++) + amd_uncore_start_hrtimer(ctx); + if (flags & PERF_EF_RELOAD) wrmsrl(hwc->event_base, (u64)local64_read(&hwc->prev_count)); hwc->state = 0; + __set_bit(hwc->idx, ctx->active_mask); wrmsrl(hwc->config_base, (hwc->config | ARCH_PERFMON_EVENTSEL_ENABLE)); perf_event_update_userpage(event); } static void amd_uncore_stop(struct perf_event *event, int flags) { + struct amd_uncore_pmu *pmu = event_to_amd_uncore_pmu(event); + struct amd_uncore_ctx *ctx = *per_cpu_ptr(pmu->ctx, event->cpu); struct hw_perf_event *hwc = &event->hw; wrmsrl(hwc->config_base, hwc->config); @@ -138,6 +187,11 @@ static void amd_uncore_stop(struct perf_event *event, int flags) event->pmu->read(event); hwc->state |= PERF_HES_UPTODATE; } + + if (!--ctx->nr_active) + amd_uncore_cancel_hrtimer(ctx); + + __clear_bit(hwc->idx, ctx->active_mask); } static int amd_uncore_add(struct perf_event *event, int flags) @@ -490,6 +544,9 @@ static int amd_uncore_ctx_init(struct amd_uncore *uncore, unsigned int cpu) goto fail; } + amd_uncore_init_hrtimer(curr); + curr->hrtimer_duration = 60LL * NSEC_PER_SEC; + cpumask_set_cpu(cpu, &pmu->active_mask); } @@ -879,12 +936,18 @@ static int amd_uncore_umc_event_init(struct perf_event *event) static void amd_uncore_umc_start(struct perf_event *event, int flags) { + struct amd_uncore_pmu *pmu = event_to_amd_uncore_pmu(event); + struct amd_uncore_ctx *ctx = *per_cpu_ptr(pmu->ctx, event->cpu); struct hw_perf_event *hwc = &event->hw; + if (!ctx->nr_active++) + amd_uncore_start_hrtimer(ctx); + if (flags & PERF_EF_RELOAD) wrmsrl(hwc->event_base, (u64)local64_read(&hwc->prev_count)); hwc->state = 0; + __set_bit(hwc->idx, ctx->active_mask); wrmsrl(hwc->config_base, (hwc->config | AMD64_PERFMON_V2_ENABLE_UMC)); perf_event_update_userpage(event); }