Commit-ID: b24e1d8d3251eb16c391415909c073e0f63ba173
Gitweb: http://git.kernel.org/tip/b24e1d8d3251eb16c391415909c073e0f63ba173
Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
AuthorDate: Wed, 22 Jul 2009 09:29:32 +0200
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Sun, 2 Aug 2009 14:17:05 +0200
perf_counter: Rework software counters
Reimplement the software counters to deal with fast moving
event sources. This means being able to generate multiple
overflows from a single 'event' as well as support throttling.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/perf_counter.c | 164 ++++++++++++++++++++++++++++---------------------
1 files changed, 94 insertions(+), 70 deletions(-)
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 199ed47..56126cf 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -3335,87 +3335,81 @@ int perf_counter_overflow(struct perf_counter *counter, int nmi,
* Generic software counter infrastructure
*/
-static void perf_swcounter_update(struct perf_counter *counter)
+/*
+ * We directly increment counter->count and keep a second value in
+ * counter->hw.period_left to count intervals. This period counter
+ * is kept in the range [-sample_period, 0] so that we can use the
+ * sign as trigger.
+ */
+
+static u64 perf_swcounter_set_period(struct perf_counter *counter)
{
struct hw_perf_counter *hwc = &counter->hw;
- u64 prev, now;
- s64 delta;
+ u64 period = hwc->last_period;
+ u64 nr, offset;
+ s64 old, val;
+
+ hwc->last_period = hwc->sample_period;
again:
- prev = atomic64_read(&hwc->prev_count);
- now = atomic64_read(&hwc->count);
- if (atomic64_cmpxchg(&hwc->prev_count, prev, now) != prev)
- goto again;
+ old = val = atomic64_read(&hwc->period_left);
+ if (val < 0)
+ return 0;
- delta = now - prev;
+ nr = div64_u64(period + val, period);
+ offset = nr * period;
+ val -= offset;
+ if (atomic64_cmpxchg(&hwc->period_left, old, val) != old)
+ goto again;
- atomic64_add(delta, &counter->count);
- atomic64_sub(delta, &hwc->period_left);
+ return nr;
}
-static void perf_swcounter_set_period(struct perf_counter *counter)
+static void perf_swcounter_overflow(struct perf_counter *counter,
+ int nmi, struct perf_sample_data *data)
{
struct hw_perf_counter *hwc = &counter->hw;
- s64 left = atomic64_read(&hwc->period_left);
- s64 period = hwc->sample_period;
+ u64 overflow;
- if (unlikely(left <= -period)) {
- left = period;
- atomic64_set(&hwc->period_left, left);
- hwc->last_period = period;
- }
+ data->period = counter->hw.last_period;
+ overflow = perf_swcounter_set_period(counter);
- if (unlikely(left <= 0)) {
- left += period;
- atomic64_add(period, &hwc->period_left);
- hwc->last_period = period;
- }
+ if (hwc->interrupts == MAX_INTERRUPTS)
+ return;
- atomic64_set(&hwc->prev_count, -left);
- atomic64_set(&hwc->count, -left);
+ for (; overflow; overflow--) {
+ if (perf_counter_overflow(counter, nmi, data)) {
+ /*
+ * We inhibit the overflow from happening when
+ * hwc->interrupts == MAX_INTERRUPTS.
+ */
+ break;
+ }
+ }
}
-static enum hrtimer_restart perf_swcounter_hrtimer(struct hrtimer *hrtimer)
+static void perf_swcounter_unthrottle(struct perf_counter *counter)
{
- enum hrtimer_restart ret = HRTIMER_RESTART;
- struct perf_sample_data data;
- struct perf_counter *counter;
- u64 period;
-
- counter = container_of(hrtimer, struct perf_counter, hw.hrtimer);
- counter->pmu->read(counter);
-
- data.addr = 0;
- data.regs = get_irq_regs();
/*
- * In case we exclude kernel IPs or are somehow not in interrupt
- * context, provide the next best thing, the user IP.
+ * Nothing to do, we already reset hwc->interrupts.
*/
- if ((counter->attr.exclude_kernel || !data.regs) &&
- !counter->attr.exclude_user)
- data.regs = task_pt_regs(current);
+}
- if (data.regs) {
- if (perf_counter_overflow(counter, 0, &data))
- ret = HRTIMER_NORESTART;
- }
+static void perf_swcounter_add(struct perf_counter *counter, u64 nr,
+ int nmi, struct perf_sample_data *data)
+{
+ struct hw_perf_counter *hwc = &counter->hw;
- period = max_t(u64, 10000, counter->hw.sample_period);
- hrtimer_forward_now(hrtimer, ns_to_ktime(period));
+ atomic64_add(nr, &counter->count);
- return ret;
-}
+ if (!hwc->sample_period)
+ return;
-static void perf_swcounter_overflow(struct perf_counter *counter,
- int nmi, struct perf_sample_data *data)
-{
- data->period = counter->hw.last_period;
+ if (!data->regs)
+ return;
- perf_swcounter_update(counter);
- perf_swcounter_set_period(counter);
- if (perf_counter_overflow(counter, nmi, data))
- /* soft-disable the counter */
- ;
+ if (!atomic64_add_negative(nr, &hwc->period_left))
+ perf_swcounter_overflow(counter, nmi, data);
}
static int perf_swcounter_is_counting(struct perf_counter *counter)
@@ -3479,15 +3473,6 @@ static int perf_swcounter_match(struct perf_counter *counter,
return 1;
}
-static void perf_swcounter_add(struct perf_counter *counter, u64 nr,
- int nmi, struct perf_sample_data *data)
-{
- int neg = atomic64_add_negative(nr, &counter->hw.count);
-
- if (counter->hw.sample_period && !neg && data->regs)
- perf_swcounter_overflow(counter, nmi, data);
-}
-
static void perf_swcounter_ctx_event(struct perf_counter_context *ctx,
enum perf_type_id type,
u32 event, u64 nr, int nmi,
@@ -3566,27 +3551,66 @@ void __perf_swcounter_event(u32 event, u64 nr, int nmi,
static void perf_swcounter_read(struct perf_counter *counter)
{
- perf_swcounter_update(counter);
}
static int perf_swcounter_enable(struct perf_counter *counter)
{
- perf_swcounter_set_period(counter);
+ struct hw_perf_counter *hwc = &counter->hw;
+
+ if (hwc->sample_period) {
+ hwc->last_period = hwc->sample_period;
+ perf_swcounter_set_period(counter);
+ }
return 0;
}
static void perf_swcounter_disable(struct perf_counter *counter)
{
- perf_swcounter_update(counter);
}
static const struct pmu perf_ops_generic = {
.enable = perf_swcounter_enable,
.disable = perf_swcounter_disable,
.read = perf_swcounter_read,
+ .unthrottle = perf_swcounter_unthrottle,
};
/*
+ * hrtimer based swcounter callback
+ */
+
+static enum hrtimer_restart perf_swcounter_hrtimer(struct hrtimer *hrtimer)
+{
+ enum hrtimer_restart ret = HRTIMER_RESTART;
+ struct perf_sample_data data;
+ struct perf_counter *counter;
+ u64 period;
+
+ counter = container_of(hrtimer, struct perf_counter, hw.hrtimer);
+ counter->pmu->read(counter);
+
+ data.addr = 0;
+ data.regs = get_irq_regs();
+ /*
+ * In case we exclude kernel IPs or are somehow not in interrupt
+ * context, provide the next best thing, the user IP.
+ */
+ if ((counter->attr.exclude_kernel || !data.regs) &&
+ !counter->attr.exclude_user)
+ data.regs = task_pt_regs(current);
+
+ if (data.regs) {
+ if (perf_counter_overflow(counter, 0, &data))
+ ret = HRTIMER_NORESTART;
+ }
+
+ period = max_t(u64, 10000, counter->hw.sample_period);
+ hrtimer_forward_now(hrtimer, ns_to_ktime(period));
+
+ return ret;
+}
+
+/*
* Software counter: cpu wall time clock
*/
--
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