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>

2 files changed, 15 insertions, 14 deletions

diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index 1a040b179b53..a56d4cf92f30 100644
--- 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 91f1ca4c01c0..f55381fbcac9 100644
--- 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)           { }