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perf_counter: frequency based adaptive irq_period

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Instead of specifying the irq_period for a counter, provide a target interrupt
frequency and dynamically adapt the irq_period to match this frequency.

[ Impact: new perf-counter attribute/feature ]

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>
LKML-Reference: <20090515132018.646195868@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra
2009-05-15 15:19:28 +02:00
committed by Ingo Molnar
parent 789f90fcf6
commit 60db5e09c1
4 changed files with 68 additions and 27 deletions
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63
kernel/perf_counter.c
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@@ -1046,6 +1046,38 @@ int perf_counter_task_enable(void)
return 0;
}
void perf_adjust_freq(struct perf_counter_context *ctx)
{
struct perf_counter *counter;
u64 irq_period;
u64 events, period;
s64 delta;
spin_lock(&ctx->lock);
list_for_each_entry(counter, &ctx->counter_list, list_entry) {
if (counter->state != PERF_COUNTER_STATE_ACTIVE)
continue;
if (!counter->hw_event.freq || !counter->hw_event.irq_freq)
continue;
events = HZ * counter->hw.interrupts * counter->hw.irq_period;
period = div64_u64(events, counter->hw_event.irq_freq);
delta = (s64)(1 + period - counter->hw.irq_period);
delta >>= 1;
irq_period = counter->hw.irq_period + delta;
if (!irq_period)
irq_period = 1;
counter->hw.irq_period = irq_period;
counter->hw.interrupts = 0;
}
spin_unlock(&ctx->lock);
}
/*
* Round-robin a context's counters:
*/
@@ -1081,6 +1113,9 @@ void perf_counter_task_tick(struct task_struct *curr, int cpu)
cpuctx = &per_cpu(perf_cpu_context, cpu);
ctx = &curr->perf_counter_ctx;
perf_adjust_freq(&cpuctx->ctx);
perf_adjust_freq(ctx);
perf_counter_cpu_sched_out(cpuctx);
__perf_counter_task_sched_out(ctx);
@@ -2382,6 +2417,8 @@ int perf_counter_overflow(struct perf_counter *counter,
int events = atomic_read(&counter->event_limit);
int ret = 0;
counter->hw.interrupts++;
/*
* XXX event_limit might not quite work as expected on inherited
* counters
@@ -2450,6 +2487,7 @@ static enum hrtimer_restart perf_swcounter_hrtimer(struct hrtimer *hrtimer)
enum hrtimer_restart ret = HRTIMER_RESTART;
struct perf_counter *counter;
struct pt_regs *regs;
u64 period;
counter = container_of(hrtimer, struct perf_counter, hw.hrtimer);
counter->pmu->read(counter);
@@ -2468,7 +2506,8 @@ static enum hrtimer_restart perf_swcounter_hrtimer(struct hrtimer *hrtimer)
ret = HRTIMER_NORESTART;
}
hrtimer_forward_now(hrtimer, ns_to_ktime(counter->hw.irq_period));
period = max_t(u64, 10000, counter->hw.irq_period);
hrtimer_forward_now(hrtimer, ns_to_ktime(period));
return ret;
}
@@ -2629,8 +2668,9 @@ static int cpu_clock_perf_counter_enable(struct perf_counter *counter)
hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
hwc->hrtimer.function = perf_swcounter_hrtimer;
if (hwc->irq_period) {
u64 period = max_t(u64, 10000, hwc->irq_period);
__hrtimer_start_range_ns(&hwc->hrtimer,
ns_to_ktime(hwc->irq_period), 0,
ns_to_ktime(period), 0,
HRTIMER_MODE_REL, 0);
}
@@ -2679,8 +2719,9 @@ static int task_clock_perf_counter_enable(struct perf_counter *counter)
hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
hwc->hrtimer.function = perf_swcounter_hrtimer;
if (hwc->irq_period) {
u64 period = max_t(u64, 10000, hwc->irq_period);
__hrtimer_start_range_ns(&hwc->hrtimer,
ns_to_ktime(hwc->irq_period), 0,
ns_to_ktime(period), 0,
HRTIMER_MODE_REL, 0);
}
@@ -2811,9 +2852,7 @@ static const struct pmu *tp_perf_counter_init(struct perf_counter *counter)
static const struct pmu *sw_perf_counter_init(struct perf_counter *counter)
{
struct perf_counter_hw_event *hw_event = &counter->hw_event;
const struct pmu *pmu = NULL;
struct hw_perf_counter *hwc = &counter->hw;
/*
* Software counters (currently) can't in general distinguish
@@ -2826,8 +2865,6 @@ static const struct pmu *sw_perf_counter_init(struct perf_counter *counter)
case PERF_COUNT_CPU_CLOCK:
pmu = &perf_ops_cpu_clock;
if (hw_event->irq_period && hw_event->irq_period < 10000)
hw_event->irq_period = 10000;
break;
case PERF_COUNT_TASK_CLOCK:
/*
@@ -2839,8 +2876,6 @@ static const struct pmu *sw_perf_counter_init(struct perf_counter *counter)
else
pmu = &perf_ops_cpu_clock;
if (hw_event->irq_period && hw_event->irq_period < 10000)
hw_event->irq_period = 10000;
break;
case PERF_COUNT_PAGE_FAULTS:
case PERF_COUNT_PAGE_FAULTS_MIN:
@@ -2854,9 +2889,6 @@ static const struct pmu *sw_perf_counter_init(struct perf_counter *counter)
break;
}
if (pmu)
hwc->irq_period = hw_event->irq_period;
return pmu;
}
@@ -2872,6 +2904,7 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event,
{
const struct pmu *pmu;
struct perf_counter *counter;
struct hw_perf_counter *hwc;
long err;
counter = kzalloc(sizeof(*counter), gfpflags);
@@ -2907,6 +2940,12 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event,
pmu = NULL;
hwc = &counter->hw;
if (hw_event->freq && hw_event->irq_freq)
hwc->irq_period = TICK_NSEC / hw_event->irq_freq;
else
hwc->irq_period = hw_event->irq_period;
/*
* we currently do not support PERF_RECORD_GROUP on inherited counters
*/