perfcounters: ratelimit performance counter interrupts

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>

diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index 1a040b1..a56d4cf 100644 (file)
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -33,9 +33,8 @@ 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;
+       unsigned long           interrupts;
        u64                     global_enable;
-       int                     throttled;
 };
 
 /*
@@ -471,13 +470,18 @@ 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
  * rules apply:
  */
 static void __smp_perf_counter_interrupt(struct pt_regs *regs, int nmi)
 {
        int bit, cpu = smp_processor_id();
-       u64 ack, status, now;
+       u64 ack, status;
        struct cpu_hw_counters *cpuc = &per_cpu(cpu_hw_counters, cpu);
 
        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);
        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);
        if (!status)
                goto out;
@@ -541,13 +540,14 @@ out:
        /*
         * 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);
 }
 
 void perf_counter_unthrottle(void)
 {
        struct cpu_hw_counters *cpuc;
+       u64 global_enable;
 
        if (!cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON))
                return;
@@ -556,12 +556,15 @@ void perf_counter_unthrottle(void)
                return;
 
        cpuc = &per_cpu(cpu_hw_counters, smp_processor_id());
-       if (cpuc->throttled) {
+       if (cpuc->interrupts >= PERFMON_MAX_INTERRUPTS) {
                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);
-               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)

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 91f1ca4..f55381f 100644 (file)
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -271,8 +271,6 @@ static inline int is_software_counter(struct perf_counter *counter)
        return !counter->hw_event.raw && counter->hw_event.type < 0;
 }
 
-#define PERFMON_MIN_PERIOD_NS 10000
-
 #else
 static inline void
 perf_counter_task_sched_in(struct task_struct *task, int cpu)          { }