From 9e350de37ac9607012fcf9c5314a28fbddf8f43c Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 10 Jun 2009 21:34:59 +0200 Subject: [PATCH] perf_counter: Accurate period data We currently log hw.sample_period for PERF_SAMPLE_PERIOD, however this is incorrect. When we adjust the period, it will only take effect the next cycle but report it for the current cycle. So when we adjust the period for every cycle, we're always wrong. Solve this by keeping track of the last_period. Signed-off-by: Peter Zijlstra Cc: Peter Zijlstra Cc: Mike Galbraith Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo LKML-Reference: Signed-off-by: Ingo Molnar --- arch/powerpc/kernel/perf_counter.c | 9 ++++++--- arch/x86/kernel/cpu/perf_counter.c | 15 ++++++++++++--- include/linux/perf_counter.h | 6 ++++-- kernel/perf_counter.c | 9 ++++++--- 4 files changed, 28 insertions(+), 11 deletions(-) diff --git a/arch/powerpc/kernel/perf_counter.c b/arch/powerpc/kernel/perf_counter.c index 5e0bf399c433..4990ce2e5f08 100644 --- a/arch/powerpc/kernel/perf_counter.c +++ b/arch/powerpc/kernel/perf_counter.c @@ -767,6 +767,7 @@ static void power_pmu_unthrottle(struct perf_counter *counter) perf_disable(); power_pmu_read(counter); left = counter->hw.sample_period; + counter->hw.last_period = left; val = 0; if (left < 0x80000000L) val = 0x80000000L - left; @@ -937,7 +938,8 @@ const struct pmu *hw_perf_counter_init(struct perf_counter *counter) counter->hw.config = events[n]; counter->hw.counter_base = cflags[n]; - atomic64_set(&counter->hw.period_left, counter->hw.sample_period); + counter->hw.last_period = counter->hw.sample_period; + atomic64_set(&counter->hw.period_left, counter->hw.last_period); /* * See if we need to reserve the PMU. @@ -1002,8 +1004,9 @@ static void record_and_restart(struct perf_counter *counter, long val, */ if (record) { struct perf_sample_data data = { - .regs = regs, - .addr = 0, + .regs = regs, + .addr = 0, + .period = counter->hw.last_period, }; if (counter->attr.sample_type & PERF_SAMPLE_ADDR) { diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c index 82a23d487f92..57ae1bec81be 100644 --- a/arch/x86/kernel/cpu/perf_counter.c +++ b/arch/x86/kernel/cpu/perf_counter.c @@ -698,6 +698,7 @@ static int __hw_perf_counter_init(struct perf_counter *counter) if (!hwc->sample_period) { hwc->sample_period = x86_pmu.max_period; + hwc->last_period = hwc->sample_period; atomic64_set(&hwc->period_left, hwc->sample_period); } @@ -880,12 +881,14 @@ x86_perf_counter_set_period(struct perf_counter *counter, if (unlikely(left <= -period)) { left = period; atomic64_set(&hwc->period_left, left); + hwc->last_period = period; ret = 1; } if (unlikely(left <= 0)) { left += period; atomic64_set(&hwc->period_left, left); + hwc->last_period = period; ret = 1; } /* @@ -1257,9 +1260,12 @@ static int amd_pmu_handle_irq(struct pt_regs *regs) if (val & (1ULL << (x86_pmu.counter_bits - 1))) continue; - /* counter overflow */ - handled = 1; - inc_irq_stat(apic_perf_irqs); + /* + * counter overflow + */ + handled = 1; + data.period = counter->hw.last_period; + if (!x86_perf_counter_set_period(counter, hwc, idx)) continue; @@ -1267,6 +1273,9 @@ static int amd_pmu_handle_irq(struct pt_regs *regs) amd_pmu_disable_counter(hwc, idx); } + if (handled) + inc_irq_stat(apic_perf_irqs); + return handled; } diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h index d8c0eb480f9a..5b966472b458 100644 --- a/include/linux/perf_counter.h +++ b/include/linux/perf_counter.h @@ -366,6 +366,7 @@ struct hw_perf_counter { }; atomic64_t prev_count; u64 sample_period; + u64 last_period; atomic64_t period_left; u64 interrupts; @@ -606,8 +607,9 @@ extern int hw_perf_group_sched_in(struct perf_counter *group_leader, extern void perf_counter_update_userpage(struct perf_counter *counter); struct perf_sample_data { - struct pt_regs *regs; - u64 addr; + struct pt_regs *regs; + u64 addr; + u64 period; }; extern int perf_counter_overflow(struct perf_counter *counter, int nmi, diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index 4fe85e804f43..8b89b40bd0f0 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -2495,7 +2495,7 @@ static void perf_counter_output(struct perf_counter *counter, int nmi, perf_output_put(&handle, cpu_entry); if (sample_type & PERF_SAMPLE_PERIOD) - perf_output_put(&handle, counter->hw.sample_period); + perf_output_put(&handle, data->period); /* * XXX PERF_SAMPLE_GROUP vs inherited counters seems difficult. @@ -3040,11 +3040,13 @@ static void perf_swcounter_set_period(struct perf_counter *counter) if (unlikely(left <= -period)) { left = period; atomic64_set(&hwc->period_left, left); + hwc->last_period = period; } if (unlikely(left <= 0)) { left += period; atomic64_add(period, &hwc->period_left); + hwc->last_period = period; } atomic64_set(&hwc->prev_count, -left); @@ -3086,8 +3088,9 @@ static void perf_swcounter_overflow(struct perf_counter *counter, int nmi, struct pt_regs *regs, u64 addr) { struct perf_sample_data data = { - .regs = regs, - .addr = addr, + .regs = regs, + .addr = addr, + .period = counter->hw.last_period, }; perf_swcounter_update(counter);