From 62b8563979273424d6ebe9201e34d1acc133ad4f Mon Sep 17 00:00:00 2001 From: Stephane Eranian Date: Wed, 3 Apr 2013 14:21:34 +0200 Subject: [PATCH] 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 Signed-off-by: Peter Zijlstra Cc: Frederic Weisbecker Cc: Arnaldo Carvalho de Melo Link: http://lkml.kernel.org/r/1364991694-5876-3-git-send-email-eranian@google.com Signed-off-by: Ingo Molnar --- include/linux/perf_event.h | 1 + kernel/events/core.c | 63 +++++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 60 insertions(+), 4 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 72138d75a60a..6fddac1b27cb 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -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 diff --git a/kernel/events/core.c b/kernel/events/core.c index 97bfac7e6f45..53d1b300116a 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -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; -- 2.11.0