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perf events: Fix swevent hrtimer sampling by keeping track of remaining time when enabling/disabling swevent hrtimers

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Make the hrtimer based events work for sysprof.

Whenever a swevent is scheduled out, the hrtimer is canceled.
When it is scheduled back in, the timer is restarted. This
happens every scheduler tick, which means the timer never
expired because it was getting repeatedly restarted over and
over with the same period.

To fix that, save the remaining time when disabling; when
reenabling, use that saved time as the period instead of the
user-specified sampling period.

Also, move the starting and stopping of the hrtimers to helper
functions instead of duplicating the code.

Signed-off-by: Søren Sandmann Pedersen <sandmann@redhat.com>
LKML-Reference: <ye8vdi7mluz.fsf@camel16.daimi.au.dk>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Soeren Sandmann 2009-09-15 14:33:08 +02:00 committed by Ingo Molnar
parent 2e600d01c1
commit 721a669b72
2 changed files with 43 additions and 22 deletions
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4
include/linux/perf_event.h
View File

@ -471,8 +471,8 @@ struct hw_perf_event {
unsigned long event_base;
int idx;
};
union { /* software */
atomic64_t count;
struct { /* software */
s64 remaining;
struct hrtimer hrtimer;
};
};

61
kernel/perf_event.c
View File

@ -3969,6 +3969,42 @@ static enum hrtimer_restart perf_swevent_hrtimer(struct hrtimer *hrtimer)
return ret;
}
static void perf_swevent_start_hrtimer(struct perf_event *event)
{
struct hw_perf_event *hwc = &event->hw;
hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
hwc->hrtimer.function = perf_swevent_hrtimer;
if (hwc->sample_period) {
u64 period;
if (hwc->remaining) {
if (hwc->remaining < 0)
period = 10000;
else
period = hwc->remaining;
hwc->remaining = 0;
} else {
period = max_t(u64, 10000, hwc->sample_period);
}
__hrtimer_start_range_ns(&hwc->hrtimer,
ns_to_ktime(period), 0,
HRTIMER_MODE_REL, 0);
}
}
static void perf_swevent_cancel_hrtimer(struct perf_event *event)
{
struct hw_perf_event *hwc = &event->hw;
if (hwc->sample_period) {
ktime_t remaining = hrtimer_get_remaining(&hwc->hrtimer);
hwc->remaining = ktime_to_ns(remaining);
hrtimer_cancel(&hwc->hrtimer);
}
}
/*
* Software event: cpu wall time clock
*/
@ -3991,22 +4027,14 @@ static int cpu_clock_perf_event_enable(struct perf_event *event)
int cpu = raw_smp_processor_id();
atomic64_set(&hwc->prev_count, cpu_clock(cpu));
hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
hwc->hrtimer.function = perf_swevent_hrtimer;
if (hwc->sample_period) {
u64 period = max_t(u64, 10000, hwc->sample_period);
__hrtimer_start_range_ns(&hwc->hrtimer,
ns_to_ktime(period), 0,
HRTIMER_MODE_REL, 0);
}
perf_swevent_start_hrtimer(event);
return 0;
}
static void cpu_clock_perf_event_disable(struct perf_event *event)
{
if (event->hw.sample_period)
hrtimer_cancel(&event->hw.hrtimer);
perf_swevent_cancel_hrtimer(event);
cpu_clock_perf_event_update(event);
}
@ -4043,22 +4071,15 @@ static int task_clock_perf_event_enable(struct perf_event *event)
now = event->ctx->time;
atomic64_set(&hwc->prev_count, now);
hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
hwc->hrtimer.function = perf_swevent_hrtimer;
if (hwc->sample_period) {
u64 period = max_t(u64, 10000, hwc->sample_period);
__hrtimer_start_range_ns(&hwc->hrtimer,
ns_to_ktime(period), 0,
HRTIMER_MODE_REL, 0);
}
perf_swevent_start_hrtimer(event);
return 0;
}
static void task_clock_perf_event_disable(struct perf_event *event)
{
if (event->hw.sample_period)
hrtimer_cancel(&event->hw.hrtimer);
perf_swevent_cancel_hrtimer(event);
task_clock_perf_event_update(event, event->ctx->time);
}