From ee06094f8279e1312fc0a31591320cc7b6f0ab1e Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Sat, 13 Dec 2008 09:00:03 +0100 Subject: [PATCH] perfcounters: restructure x86 counter math Impact: restructure code Change counter math from absolute values to clear delta logic. We try to extract elapsed deltas from the raw hw counter - and put that into the generic counter. Signed-off-by: Ingo Molnar --- arch/x86/Kconfig | 2 +- arch/x86/kernel/cpu/perf_counter.c | 230 ++++++++++++++++------------- include/linux/perf_counter.h | 15 +- kernel/perf_counter.c | 68 +-------- 4 files changed, 137 insertions(+), 178 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index f2fdc186724..fe94490bab6 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -643,7 +643,7 @@ config X86_UP_IOAPIC config X86_LOCAL_APIC def_bool y depends on X86_64 || (X86_32 && (X86_UP_APIC || (SMP && !X86_VOYAGER) || X86_GENERICARCH)) - select HAVE_PERF_COUNTERS + select HAVE_PERF_COUNTERS if (!M386 && !M486) config X86_IO_APIC def_bool y diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c index b903f8df72b..5afae13d8d5 100644 --- a/arch/x86/kernel/cpu/perf_counter.c +++ b/arch/x86/kernel/cpu/perf_counter.c @@ -53,6 +53,48 @@ const int intel_perfmon_event_map[] = const int max_intel_perfmon_events = ARRAY_SIZE(intel_perfmon_event_map); +/* + * Propagate counter elapsed time into the generic counter. + * Can only be executed on the CPU where the counter is active. + * Returns the delta events processed. + */ +static void +x86_perf_counter_update(struct perf_counter *counter, + struct hw_perf_counter *hwc, int idx) +{ + u64 prev_raw_count, new_raw_count, delta; + + WARN_ON_ONCE(counter->state != PERF_COUNTER_STATE_ACTIVE); + /* + * Careful: an NMI might modify the previous counter value. + * + * Our tactic to handle this is to first atomically read and + * exchange a new raw count - then add that new-prev delta + * count to the generic counter atomically: + */ +again: + prev_raw_count = atomic64_read(&hwc->prev_count); + rdmsrl(hwc->counter_base + idx, new_raw_count); + + if (atomic64_cmpxchg(&hwc->prev_count, prev_raw_count, + new_raw_count) != prev_raw_count) + goto again; + + /* + * Now we have the new raw value and have updated the prev + * timestamp already. We can now calculate the elapsed delta + * (counter-)time and add that to the generic counter. + * + * Careful, not all hw sign-extends above the physical width + * of the count, so we do that by clipping the delta to 32 bits: + */ + delta = (u64)(u32)((s32)new_raw_count - (s32)prev_raw_count); + WARN_ON_ONCE((int)delta < 0); + + atomic64_add(delta, &counter->count); + atomic64_sub(delta, &hwc->period_left); +} + /* * Setup the hardware configuration for a given hw_event_type */ @@ -90,10 +132,10 @@ static int __hw_perf_counter_init(struct perf_counter *counter) * so we install an artificial 1<<31 period regardless of * the generic counter period: */ - if (!hwc->irq_period) + if ((s64)hwc->irq_period <= 0 || hwc->irq_period > 0x7FFFFFFF) hwc->irq_period = 0x7FFFFFFF; - hwc->next_count = -(s32)hwc->irq_period; + atomic64_set(&hwc->period_left, hwc->irq_period); /* * Raw event type provide the config in the event structure @@ -118,12 +160,6 @@ void hw_perf_enable_all(void) wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, perf_counter_mask, 0); } -void hw_perf_restore(u64 ctrl) -{ - wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, ctrl, 0); -} -EXPORT_SYMBOL_GPL(hw_perf_restore); - u64 hw_perf_save_disable(void) { u64 ctrl; @@ -134,27 +170,74 @@ u64 hw_perf_save_disable(void) } EXPORT_SYMBOL_GPL(hw_perf_save_disable); +void hw_perf_restore(u64 ctrl) +{ + wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, ctrl, 0); +} +EXPORT_SYMBOL_GPL(hw_perf_restore); + static inline void -__x86_perf_counter_disable(struct hw_perf_counter *hwc, unsigned int idx) +__x86_perf_counter_disable(struct perf_counter *counter, + struct hw_perf_counter *hwc, unsigned int idx) { - wrmsr(hwc->config_base + idx, hwc->config, 0); + int err; + + err = wrmsr_safe(hwc->config_base + idx, hwc->config, 0); + WARN_ON_ONCE(err); } -static DEFINE_PER_CPU(u64, prev_next_count[MAX_HW_COUNTERS]); +static DEFINE_PER_CPU(u64, prev_left[MAX_HW_COUNTERS]); -static void __hw_perf_counter_set_period(struct hw_perf_counter *hwc, int idx) +/* + * Set the next IRQ period, based on the hwc->period_left value. + * To be called with the counter disabled in hw: + */ +static void +__hw_perf_counter_set_period(struct perf_counter *counter, + struct hw_perf_counter *hwc, int idx) { - per_cpu(prev_next_count[idx], smp_processor_id()) = hwc->next_count; + s32 left = atomic64_read(&hwc->period_left); + s32 period = hwc->irq_period; + + WARN_ON_ONCE(period <= 0); + + /* + * If we are way outside a reasoable range then just skip forward: + */ + if (unlikely(left <= -period)) { + left = period; + atomic64_set(&hwc->period_left, left); + } + + if (unlikely(left <= 0)) { + left += period; + atomic64_set(&hwc->period_left, left); + } - wrmsr(hwc->counter_base + idx, hwc->next_count, 0); + WARN_ON_ONCE(left <= 0); + + per_cpu(prev_left[idx], smp_processor_id()) = left; + + /* + * The hw counter starts counting from this counter offset, + * mark it to be able to extra future deltas: + */ + atomic64_set(&hwc->prev_count, (u64)(s64)-left); + + wrmsr(hwc->counter_base + idx, -left, 0); } -static void __x86_perf_counter_enable(struct hw_perf_counter *hwc, int idx) +static void +__x86_perf_counter_enable(struct perf_counter *counter, + struct hw_perf_counter *hwc, int idx) { wrmsr(hwc->config_base + idx, hwc->config | ARCH_PERFMON_EVENTSEL0_ENABLE, 0); } +/* + * Find a PMC slot for the freshly enabled / scheduled in counter: + */ static void x86_perf_counter_enable(struct perf_counter *counter) { struct cpu_hw_counters *cpuc = &__get_cpu_var(cpu_hw_counters); @@ -170,55 +253,17 @@ static void x86_perf_counter_enable(struct perf_counter *counter) perf_counters_lapic_init(hwc->nmi); - __x86_perf_counter_disable(hwc, idx); + __x86_perf_counter_disable(counter, hwc, idx); cpuc->counters[idx] = counter; - __hw_perf_counter_set_period(hwc, idx); - __x86_perf_counter_enable(hwc, idx); -} - -static void __hw_perf_save_counter(struct perf_counter *counter, - struct hw_perf_counter *hwc, int idx) -{ - s64 raw = -1; - s64 delta; - - /* - * Get the raw hw counter value: - */ - rdmsrl(hwc->counter_base + idx, raw); - - /* - * Rebase it to zero (it started counting at -irq_period), - * to see the delta since ->prev_count: - */ - delta = (s64)hwc->irq_period + (s64)(s32)raw; - - atomic64_counter_set(counter, hwc->prev_count + delta); - - /* - * Adjust the ->prev_count offset - if we went beyond - * irq_period of units, then we got an IRQ and the counter - * was set back to -irq_period: - */ - while (delta >= (s64)hwc->irq_period) { - hwc->prev_count += hwc->irq_period; - delta -= (s64)hwc->irq_period; - } - - /* - * Calculate the next raw counter value we'll write into - * the counter at the next sched-in time: - */ - delta -= (s64)hwc->irq_period; - - hwc->next_count = (s32)delta; + __hw_perf_counter_set_period(counter, hwc, idx); + __x86_perf_counter_enable(counter, hwc, idx); } void perf_counter_print_debug(void) { - u64 ctrl, status, overflow, pmc_ctrl, pmc_count, next_count; + u64 ctrl, status, overflow, pmc_ctrl, pmc_count, prev_left; int cpu, idx; if (!nr_hw_counters) @@ -241,14 +286,14 @@ void perf_counter_print_debug(void) rdmsrl(MSR_ARCH_PERFMON_EVENTSEL0 + idx, pmc_ctrl); rdmsrl(MSR_ARCH_PERFMON_PERFCTR0 + idx, pmc_count); - next_count = per_cpu(prev_next_count[idx], cpu); + prev_left = per_cpu(prev_left[idx], cpu); printk(KERN_INFO "CPU#%d: PMC%d ctrl: %016llx\n", cpu, idx, pmc_ctrl); printk(KERN_INFO "CPU#%d: PMC%d count: %016llx\n", cpu, idx, pmc_count); - printk(KERN_INFO "CPU#%d: PMC%d next: %016llx\n", - cpu, idx, next_count); + printk(KERN_INFO "CPU#%d: PMC%d left: %016llx\n", + cpu, idx, prev_left); } local_irq_enable(); } @@ -259,29 +304,16 @@ static void x86_perf_counter_disable(struct perf_counter *counter) struct hw_perf_counter *hwc = &counter->hw; unsigned int idx = hwc->idx; - __x86_perf_counter_disable(hwc, idx); + __x86_perf_counter_disable(counter, hwc, idx); clear_bit(idx, cpuc->used); cpuc->counters[idx] = NULL; - __hw_perf_save_counter(counter, hwc, idx); -} -static void x86_perf_counter_read(struct perf_counter *counter) -{ - struct hw_perf_counter *hwc = &counter->hw; - unsigned long addr = hwc->counter_base + hwc->idx; - s64 offs, val = -1LL; - s32 val32; - - /* Careful: NMI might modify the counter offset */ - do { - offs = hwc->prev_count; - rdmsrl(addr, val); - } while (offs != hwc->prev_count); - - val32 = (s32) val; - val = (s64)hwc->irq_period + (s64)val32; - atomic64_counter_set(counter, hwc->prev_count + val); + /* + * Drain the remaining delta count out of a counter + * that we are disabling: + */ + x86_perf_counter_update(counter, hwc, idx); } static void perf_store_irq_data(struct perf_counter *counter, u64 data) @@ -299,7 +331,8 @@ static void perf_store_irq_data(struct perf_counter *counter, u64 data) } /* - * NMI-safe enable method: + * Save and restart an expired counter. Called by NMI contexts, + * so it has to be careful about preempting normal counter ops: */ static void perf_save_and_restart(struct perf_counter *counter) { @@ -309,45 +342,25 @@ static void perf_save_and_restart(struct perf_counter *counter) rdmsrl(MSR_ARCH_PERFMON_EVENTSEL0 + idx, pmc_ctrl); - __hw_perf_save_counter(counter, hwc, idx); - __hw_perf_counter_set_period(hwc, idx); + x86_perf_counter_update(counter, hwc, idx); + __hw_perf_counter_set_period(counter, hwc, idx); if (pmc_ctrl & ARCH_PERFMON_EVENTSEL0_ENABLE) - __x86_perf_counter_enable(hwc, idx); + __x86_perf_counter_enable(counter, hwc, idx); } static void perf_handle_group(struct perf_counter *sibling, u64 *status, u64 *overflown) { struct perf_counter *counter, *group_leader = sibling->group_leader; - int bit; - - /* - * Store the counter's own timestamp first: - */ - perf_store_irq_data(sibling, sibling->hw_event.type); - perf_store_irq_data(sibling, atomic64_counter_read(sibling)); /* - * Then store sibling timestamps (if any): + * Store sibling timestamps (if any): */ list_for_each_entry(counter, &group_leader->sibling_list, list_entry) { - if (counter->state != PERF_COUNTER_STATE_ACTIVE) { - /* - * When counter was not in the overflow mask, we have to - * read it from hardware. We read it as well, when it - * has not been read yet and clear the bit in the - * status mask. - */ - bit = counter->hw.idx; - if (!test_bit(bit, (unsigned long *) overflown) || - test_bit(bit, (unsigned long *) status)) { - clear_bit(bit, (unsigned long *) status); - perf_save_and_restart(counter); - } - } + x86_perf_counter_update(counter, &counter->hw, counter->hw.idx); perf_store_irq_data(sibling, counter->hw_event.type); - perf_store_irq_data(sibling, atomic64_counter_read(counter)); + perf_store_irq_data(sibling, atomic64_read(&counter->count)); } } @@ -540,6 +553,11 @@ void __init init_hw_perf_counters(void) perf_counters_initialized = true; } +static void x86_perf_counter_read(struct perf_counter *counter) +{ + x86_perf_counter_update(counter, &counter->hw, counter->hw.idx); +} + static const struct hw_perf_counter_ops x86_perf_counter_ops = { .hw_perf_counter_enable = x86_perf_counter_enable, .hw_perf_counter_disable = x86_perf_counter_disable, diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h index 8cb095fa442..72460289c65 100644 --- a/include/linux/perf_counter.h +++ b/include/linux/perf_counter.h @@ -91,14 +91,16 @@ struct perf_counter_hw_event { * struct hw_perf_counter - performance counter hardware details: */ struct hw_perf_counter { +#ifdef CONFIG_PERF_COUNTERS u64 config; unsigned long config_base; unsigned long counter_base; int nmi; unsigned int idx; - u64 prev_count; + atomic64_t prev_count; u64 irq_period; - s32 next_count; + atomic64_t period_left; +#endif }; /* @@ -140,17 +142,15 @@ enum perf_counter_active_state { * struct perf_counter - performance counter kernel representation: */ struct perf_counter { +#ifdef CONFIG_PERF_COUNTERS struct list_head list_entry; struct list_head sibling_list; struct perf_counter *group_leader; const struct hw_perf_counter_ops *hw_ops; enum perf_counter_active_state state; -#if BITS_PER_LONG == 64 atomic64_t count; -#else - atomic_t count32[2]; -#endif + struct perf_counter_hw_event hw_event; struct hw_perf_counter hw; @@ -172,6 +172,7 @@ struct perf_counter { struct perf_data *irqdata; struct perf_data *usrdata; struct perf_data data[2]; +#endif }; /** @@ -220,8 +221,6 @@ extern void perf_counter_notify(struct pt_regs *regs); extern void perf_counter_print_debug(void); extern u64 hw_perf_save_disable(void); extern void hw_perf_restore(u64 ctrl); -extern void atomic64_counter_set(struct perf_counter *counter, u64 val64); -extern u64 atomic64_counter_read(struct perf_counter *counter); extern int perf_counter_task_disable(void); extern int perf_counter_task_enable(void); diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index 559130b8774..416861ce8b2 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -44,67 +44,9 @@ hw_perf_counter_init(struct perf_counter *counter) } u64 __weak hw_perf_save_disable(void) { return 0; } -void __weak hw_perf_restore(u64 ctrl) { } +void __weak hw_perf_restore(u64 ctrl) { } void __weak hw_perf_counter_setup(void) { } -#if BITS_PER_LONG == 64 - -/* - * Read the cached counter in counter safe against cross CPU / NMI - * modifications. 64 bit version - no complications. - */ -static inline u64 perf_counter_read_safe(struct perf_counter *counter) -{ - return (u64) atomic64_read(&counter->count); -} - -void atomic64_counter_set(struct perf_counter *counter, u64 val) -{ - atomic64_set(&counter->count, val); -} - -u64 atomic64_counter_read(struct perf_counter *counter) -{ - return atomic64_read(&counter->count); -} - -#else - -/* - * Read the cached counter in counter safe against cross CPU / NMI - * modifications. 32 bit version. - */ -static u64 perf_counter_read_safe(struct perf_counter *counter) -{ - u32 cntl, cnth; - - local_irq_disable(); - do { - cnth = atomic_read(&counter->count32[1]); - cntl = atomic_read(&counter->count32[0]); - } while (cnth != atomic_read(&counter->count32[1])); - - local_irq_enable(); - - return cntl | ((u64) cnth) << 32; -} - -void atomic64_counter_set(struct perf_counter *counter, u64 val64) -{ - u32 *val32 = (void *)&val64; - - atomic_set(counter->count32 + 0, *(val32 + 0)); - atomic_set(counter->count32 + 1, *(val32 + 1)); -} - -u64 atomic64_counter_read(struct perf_counter *counter) -{ - return atomic_read(counter->count32 + 0) | - (u64) atomic_read(counter->count32 + 1) << 32; -} - -#endif - static void list_add_counter(struct perf_counter *counter, struct perf_counter_context *ctx) { @@ -280,11 +222,11 @@ static void __perf_install_in_context(void *info) ctx->nr_counters++; if (cpuctx->active_oncpu < perf_max_counters) { - counter->hw_ops->hw_perf_counter_enable(counter); counter->state = PERF_COUNTER_STATE_ACTIVE; counter->oncpu = cpu; ctx->nr_active++; cpuctx->active_oncpu++; + counter->hw_ops->hw_perf_counter_enable(counter); } if (!ctx->task && cpuctx->max_pertask) @@ -624,7 +566,7 @@ static u64 perf_counter_read(struct perf_counter *counter) __hw_perf_counter_read, counter, 1); } - return perf_counter_read_safe(counter); + return atomic64_read(&counter->count); } /* @@ -921,7 +863,7 @@ static void cpu_clock_perf_counter_read(struct perf_counter *counter) { int cpu = raw_smp_processor_id(); - atomic64_counter_set(counter, cpu_clock(cpu)); + atomic64_set(&counter->count, cpu_clock(cpu)); } static const struct hw_perf_counter_ops perf_ops_cpu_clock = { @@ -940,7 +882,7 @@ static void task_clock_perf_counter_disable(struct perf_counter *counter) static void task_clock_perf_counter_read(struct perf_counter *counter) { - atomic64_counter_set(counter, current->se.sum_exec_runtime); + atomic64_set(&counter->count, current->se.sum_exec_runtime); } static const struct hw_perf_counter_ops perf_ops_task_clock = { -- 2.39.5