perf_counter: Generic per counter interrupt throttle
Introduce a generic per counter interrupt throttle.
This uses the perf_counter_overflow() quick disable to throttle a specific
counter when its going too fast when a pmu->unthrottle() method is provided
which can undo the quick disable.
Power needs to implement both the quick disable and the unthrottle method.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <20090525153931.703093461@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 14b1fe9..ec9c4007 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -46,6 +46,7 @@
int sysctl_perf_counter_priv __read_mostly; /* do we need to be privileged */
int sysctl_perf_counter_mlock __read_mostly = 512; /* 'free' kb per user */
+int sysctl_perf_counter_limit __read_mostly = 100000; /* max NMIs per second */
/*
* Lock for (sysadmin-configurable) counter reservations:
@@ -1066,12 +1067,15 @@
__perf_counter_sched_in(ctx, cpuctx, cpu);
}
+#define MAX_INTERRUPTS (~0ULL)
+
+static void perf_log_throttle(struct perf_counter *counter, int enable);
static void perf_log_period(struct perf_counter *counter, u64 period);
static void perf_adjust_freq(struct perf_counter_context *ctx)
{
struct perf_counter *counter;
- u64 irq_period;
+ u64 interrupts, irq_period;
u64 events, period;
s64 delta;
@@ -1080,10 +1084,19 @@
if (counter->state != PERF_COUNTER_STATE_ACTIVE)
continue;
+ interrupts = counter->hw.interrupts;
+ counter->hw.interrupts = 0;
+
+ if (interrupts == MAX_INTERRUPTS) {
+ perf_log_throttle(counter, 1);
+ counter->pmu->unthrottle(counter);
+ interrupts = 2*sysctl_perf_counter_limit/HZ;
+ }
+
if (!counter->hw_event.freq || !counter->hw_event.irq_freq)
continue;
- events = HZ * counter->hw.interrupts * counter->hw.irq_period;
+ events = HZ * interrupts * counter->hw.irq_period;
period = div64_u64(events, counter->hw_event.irq_freq);
delta = (s64)(1 + period - counter->hw.irq_period);
@@ -1097,7 +1110,6 @@
perf_log_period(counter, irq_period);
counter->hw.irq_period = irq_period;
- counter->hw.interrupts = 0;
}
spin_unlock(&ctx->lock);
}
@@ -2544,6 +2556,35 @@
}
/*
+ * IRQ throttle logging
+ */
+
+static void perf_log_throttle(struct perf_counter *counter, int enable)
+{
+ struct perf_output_handle handle;
+ int ret;
+
+ struct {
+ struct perf_event_header header;
+ u64 time;
+ } throttle_event = {
+ .header = {
+ .type = PERF_EVENT_THROTTLE + 1,
+ .misc = 0,
+ .size = sizeof(throttle_event),
+ },
+ .time = sched_clock(),
+ };
+
+ ret = perf_output_begin(&handle, counter, sizeof(throttle_event), 0, 0);
+ if (ret)
+ return;
+
+ perf_output_put(&handle, throttle_event);
+ perf_output_end(&handle);
+}
+
+/*
* Generic counter overflow handling.
*/
@@ -2551,9 +2592,19 @@
int nmi, struct pt_regs *regs, u64 addr)
{
int events = atomic_read(&counter->event_limit);
+ int throttle = counter->pmu->unthrottle != NULL;
int ret = 0;
- counter->hw.interrupts++;
+ if (!throttle) {
+ counter->hw.interrupts++;
+ } else if (counter->hw.interrupts != MAX_INTERRUPTS) {
+ counter->hw.interrupts++;
+ if (HZ*counter->hw.interrupts > (u64)sysctl_perf_counter_limit) {
+ counter->hw.interrupts = MAX_INTERRUPTS;
+ perf_log_throttle(counter, 0);
+ ret = 1;
+ }
+ }
/*
* XXX event_limit might not quite work as expected on inherited