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perfcounters: ratelimit performance counter interrupts

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Ratelimit performance counter interrupts to 100KHz per CPU.

This replaces the irq-delta-time based method.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Mike Galbraith 2009-01-23 14:36:16 +01:00 • committed by Ingo Molnar
parent 1b023a96d9
commit 4b39fd9685
2 changed files with 15 additions and 14 deletions
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27
arch/x86/kernel/cpu/perf_counter.c
View file

@ -33,9 +33,8 @@ static int nr_counters_fixed __read_mostly;
struct cpu_hw_counters { struct cpu_hw_counters {
struct perf_counter *counters[X86_PMC_IDX_MAX]; struct perf_counter *counters[X86_PMC_IDX_MAX];
unsigned long used[BITS_TO_LONGS(X86_PMC_IDX_MAX)]; unsigned long used[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
u64 last_interrupt; unsigned long interrupts;
u64 global_enable; u64 global_enable;
int throttled;
}; };
/* /*
@ -470,6 +469,11 @@ perf_handle_group(struct perf_counter *sibling, u64 *status, u64 *overflown)
} }
} }
/*
* Maximum interrupt frequency of 100KHz per CPU
*/
#define PERFMON_MAX_INTERRUPTS 100000/HZ
/* /*
* This handler is triggered by the local APIC, so the APIC IRQ handling * This handler is triggered by the local APIC, so the APIC IRQ handling
* rules apply: * rules apply:
@ -477,7 +481,7 @@ perf_handle_group(struct perf_counter *sibling, u64 *status, u64 *overflown)
static void __smp_perf_counter_interrupt(struct pt_regs *regs, int nmi) static void __smp_perf_counter_interrupt(struct pt_regs *regs, int nmi)
{ {
int bit, cpu = smp_processor_id(); int bit, cpu = smp_processor_id();
u64 ack, status, now; u64 ack, status;
struct cpu_hw_counters *cpuc = &per_cpu(cpu_hw_counters, cpu); struct cpu_hw_counters *cpuc = &per_cpu(cpu_hw_counters, cpu);
rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable); rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable);
@ -486,11 +490,6 @@ static void __smp_perf_counter_interrupt(struct pt_regs *regs, int nmi)
wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, 0); wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, 0);
ack_APIC_irq(); ack_APIC_irq();
now = sched_clock();
if (now - cpuc->last_interrupt < PERFMON_MIN_PERIOD_NS)
cpuc->throttled = 1;
cpuc->last_interrupt = now;
rdmsrl(MSR_CORE_PERF_GLOBAL_STATUS, status); rdmsrl(MSR_CORE_PERF_GLOBAL_STATUS, status);
if (!status) if (!status)
goto out; goto out;
@ -541,13 +540,14 @@ out:
/* /*
* Restore - do not reenable when global enable is off or throttled: * Restore - do not reenable when global enable is off or throttled:
*/ */
if (!cpuc->throttled) if (++cpuc->interrupts < PERFMON_MAX_INTERRUPTS)
wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable); wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable);
} }
void perf_counter_unthrottle(void) void perf_counter_unthrottle(void)
{ {
struct cpu_hw_counters *cpuc; struct cpu_hw_counters *cpuc;
u64 global_enable;
if (!cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) if (!cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON))
return; return;
@ -556,12 +556,15 @@ void perf_counter_unthrottle(void)
return; return;
cpuc = &per_cpu(cpu_hw_counters, smp_processor_id()); cpuc = &per_cpu(cpu_hw_counters, smp_processor_id());
if (cpuc->throttled) { if (cpuc->interrupts >= PERFMON_MAX_INTERRUPTS) {
if (printk_ratelimit()) if (printk_ratelimit())
printk(KERN_WARNING "PERFMON: max event frequency exceeded!\n"); printk(KERN_WARNING "PERFMON: max interrupts exceeded!\n");
wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable); wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable);
cpuc->throttled = 0;
} }
rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, global_enable);
if (unlikely(cpuc->global_enable && !global_enable))
wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable);
cpuc->interrupts = 0;
} }
void smp_perf_counter_interrupt(struct pt_regs *regs) void smp_perf_counter_interrupt(struct pt_regs *regs)

2
include/linux/perf_counter.h
View file

@ -271,8 +271,6 @@ static inline int is_software_counter(struct perf_counter *counter)
return !counter->hw_event.raw && counter->hw_event.type < 0; return !counter->hw_event.raw && counter->hw_event.type < 0;
} }
#define PERFMON_MIN_PERIOD_NS 10000
#else #else
static inline void static inline void
perf_counter_task_sched_in(struct task_struct *task, int cpu) { } perf_counter_task_sched_in(struct task_struct *task, int cpu) { }