diff options
| author | Mike Galbraith <efault@gmx.de> | 2009-01-23 10:13:01 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-01-23 11:33:18 +0100 |
| commit | 1b023a96d9b44f50f4d8ff28c15f5b80e354760f (patch) | |
| tree | 8b6a5956c4461c13c2e2b3769096afac5b767524 /arch | |
| parent | 05e3423c8577126800841bc55de8a509f2433dca (diff) | |
perfcounters: throttle on too high IRQ rates
Starting kerneltop with only -c 100 seems to be a bad idea, it can
easily lock the system due to perfcounter IRQ overload.
So add throttling: if a new IRQ arrives in a shorter than
PERFMON_MIN_PERIOD_NS time, turn off perfcounters and untrottle them
from the next timer tick.
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/apic.c | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/perf_counter.c | 38 |
2 files changed, 34 insertions, 6 deletions
diff --git a/arch/x86/kernel/apic.c b/arch/x86/kernel/apic.c index 7b434e5b14c..849c23009bf 100644 --- a/arch/x86/kernel/apic.c +++ b/arch/x86/kernel/apic.c @@ -781,6 +781,8 @@ static void local_apic_timer_interrupt(void) inc_irq_stat(apic_timer_irqs); evt->event_handler(evt); + + perf_counter_unthrottle(); } /* diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c index 9376771f757..1a040b179b5 100644 --- a/arch/x86/kernel/cpu/perf_counter.c +++ b/arch/x86/kernel/cpu/perf_counter.c @@ -33,6 +33,9 @@ static int nr_counters_fixed __read_mostly; struct cpu_hw_counters { struct perf_counter *counters[X86_PMC_IDX_MAX]; unsigned long used[BITS_TO_LONGS(X86_PMC_IDX_MAX)]; + u64 last_interrupt; + u64 global_enable; + int throttled; }; /* @@ -474,16 +477,19 @@ perf_handle_group(struct perf_counter *sibling, u64 *status, u64 *overflown) static void __smp_perf_counter_interrupt(struct pt_regs *regs, int nmi) { int bit, cpu = smp_processor_id(); - u64 ack, status, saved_global; - struct cpu_hw_counters *cpuc; + u64 ack, status, now; + struct cpu_hw_counters *cpuc = &per_cpu(cpu_hw_counters, cpu); - rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, saved_global); + rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable); /* Disable counters globally */ wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, 0); ack_APIC_irq(); - cpuc = &per_cpu(cpu_hw_counters, cpu); + 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); if (!status) @@ -533,9 +539,29 @@ again: goto again; out: /* - * Restore - do not reenable when global enable is off: + * Restore - do not reenable when global enable is off or throttled: */ - wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, saved_global); + if (!cpuc->throttled) + wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable); +} + +void perf_counter_unthrottle(void) +{ + struct cpu_hw_counters *cpuc; + + if (!cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) + return; + + if (unlikely(!perf_counters_initialized)) + return; + + cpuc = &per_cpu(cpu_hw_counters, smp_processor_id()); + if (cpuc->throttled) { + if (printk_ratelimit()) + printk(KERN_WARNING "PERFMON: max event frequency exceeded!\n"); + wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable); + cpuc->throttled = 0; + } } void smp_perf_counter_interrupt(struct pt_regs *regs) |