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perf: Add sysfs entry to adjust multiplexing interval per PMU

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This patch adds /sys/device/xxx/perf_event_mux_interval_ms to ajust
the multiplexing interval per PMU. The unit is milliseconds. Value has
to be >= 1.

In the 4th version, we renamed the sysfs file to be more consistent
with the other /proc/sys/kernel entries for perf_events.

In the 5th version, we handle the reprogramming of the hrtimer using
hrtimer_forward_now(). That way, we sync up to new timer value quickly
(suggested by Jiri Olsa).

Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: http://lkml.kernel.org/r/1364991694-5876-3-git-send-email-eranian@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Stephane Eranian 2013-04-03 14:21:34 +02:00 committed by Ingo Molnar
parent 9e6302056f
commit 62b8563979
2 changed files with 60 additions and 4 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

1
include/linux/perf_event.h
View file

@ -194,6 +194,7 @@ struct pmu {
int * __percpu pmu_disable_count;
struct perf_cpu_context * __percpu pmu_cpu_context;
int task_ctx_nr;
int hrtimer_interval_ms;
/*
* Fully disable/enable this PMU, can be used to protect from the PMI

63
kernel/events/core.c
View file

@ -723,13 +723,21 @@ static void __perf_cpu_hrtimer_init(struct perf_cpu_context *cpuctx, int cpu)
{
struct hrtimer *hr = &cpuctx->hrtimer;
struct pmu *pmu = cpuctx->ctx.pmu;
int timer;
/* no multiplexing needed for SW PMU */
if (pmu->task_ctx_nr == perf_sw_context)
return;
cpuctx->hrtimer_interval =
ns_to_ktime(NSEC_PER_MSEC * PERF_CPU_HRTIMER);
/*
* check default is sane, if not set then force to
* default interval (1/tick)
*/
timer = pmu->hrtimer_interval_ms;
if (timer < 1)
timer = pmu->hrtimer_interval_ms = PERF_CPU_HRTIMER;
cpuctx->hrtimer_interval = ns_to_ktime(NSEC_PER_MSEC * timer);
hrtimer_init(hr, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
hr->function = perf_cpu_hrtimer_handler;
@ -6001,9 +6009,56 @@ type_show(struct device *dev, struct device_attribute *attr, char *page)
return snprintf(page, PAGE_SIZE-1, "%d\n", pmu->type);
}
static ssize_t
perf_event_mux_interval_ms_show(struct device *dev,
struct device_attribute *attr,
char *page)
{
struct pmu *pmu = dev_get_drvdata(dev);
return snprintf(page, PAGE_SIZE-1, "%d\n", pmu->hrtimer_interval_ms);
}
static ssize_t
perf_event_mux_interval_ms_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct pmu *pmu = dev_get_drvdata(dev);
int timer, cpu, ret;
ret = kstrtoint(buf, 0, &timer);
if (ret)
return ret;
if (timer < 1)
return -EINVAL;
/* same value, noting to do */
if (timer == pmu->hrtimer_interval_ms)
return count;
pmu->hrtimer_interval_ms = timer;
/* update all cpuctx for this PMU */
for_each_possible_cpu(cpu) {
struct perf_cpu_context *cpuctx;
cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
cpuctx->hrtimer_interval = ns_to_ktime(NSEC_PER_MSEC * timer);
if (hrtimer_active(&cpuctx->hrtimer))
hrtimer_forward_now(&cpuctx->hrtimer, cpuctx->hrtimer_interval);
}
return count;
}
#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
static struct device_attribute pmu_dev_attrs[] = {
__ATTR_RO(type),
__ATTR_NULL,
__ATTR_RO(type),
__ATTR_RW(perf_event_mux_interval_ms),
__ATTR_NULL,
};
static int pmu_bus_running;