perf: Add sysfs entry to adjust multiplexing interval per PMU
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>
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@ -194,6 +194,7 @@ struct pmu {
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int * __percpu pmu_disable_count;
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struct perf_cpu_context * __percpu pmu_cpu_context;
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int task_ctx_nr;
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int hrtimer_interval_ms;
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/*
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* Fully disable/enable this PMU, can be used to protect from the PMI
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@ -723,13 +723,21 @@ static void __perf_cpu_hrtimer_init(struct perf_cpu_context *cpuctx, int cpu)
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{
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struct hrtimer *hr = &cpuctx->hrtimer;
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struct pmu *pmu = cpuctx->ctx.pmu;
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int timer;
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/* no multiplexing needed for SW PMU */
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if (pmu->task_ctx_nr == perf_sw_context)
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return;
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cpuctx->hrtimer_interval =
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ns_to_ktime(NSEC_PER_MSEC * PERF_CPU_HRTIMER);
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/*
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* check default is sane, if not set then force to
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* default interval (1/tick)
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*/
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timer = pmu->hrtimer_interval_ms;
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if (timer < 1)
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timer = pmu->hrtimer_interval_ms = PERF_CPU_HRTIMER;
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cpuctx->hrtimer_interval = ns_to_ktime(NSEC_PER_MSEC * timer);
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hrtimer_init(hr, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
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hr->function = perf_cpu_hrtimer_handler;
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@ -6001,9 +6009,56 @@ type_show(struct device *dev, struct device_attribute *attr, char *page)
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return snprintf(page, PAGE_SIZE-1, "%d\n", pmu->type);
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}
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static ssize_t
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perf_event_mux_interval_ms_show(struct device *dev,
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struct device_attribute *attr,
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char *page)
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{
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struct pmu *pmu = dev_get_drvdata(dev);
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return snprintf(page, PAGE_SIZE-1, "%d\n", pmu->hrtimer_interval_ms);
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}
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static ssize_t
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perf_event_mux_interval_ms_store(struct device *dev,
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struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct pmu *pmu = dev_get_drvdata(dev);
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int timer, cpu, ret;
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ret = kstrtoint(buf, 0, &timer);
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if (ret)
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return ret;
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if (timer < 1)
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return -EINVAL;
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/* same value, noting to do */
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if (timer == pmu->hrtimer_interval_ms)
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return count;
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pmu->hrtimer_interval_ms = timer;
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/* update all cpuctx for this PMU */
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for_each_possible_cpu(cpu) {
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struct perf_cpu_context *cpuctx;
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cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
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cpuctx->hrtimer_interval = ns_to_ktime(NSEC_PER_MSEC * timer);
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if (hrtimer_active(&cpuctx->hrtimer))
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hrtimer_forward_now(&cpuctx->hrtimer, cpuctx->hrtimer_interval);
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}
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return count;
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}
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#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
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static struct device_attribute pmu_dev_attrs[] = {
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__ATTR_RO(type),
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__ATTR_NULL,
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__ATTR_RO(type),
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__ATTR_RW(perf_event_mux_interval_ms),
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__ATTR_NULL,
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};
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static int pmu_bus_running;
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