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Commit adcd5a56 authored by Neil Leeder's avatar Neil Leeder Committed by Stephen Boyd
Browse files

Perf: keep events across hotplug 



Keep event list alive across a CPU hotplug so that perf
can resume when the CPU comes back online. Bring a CPU
online when exiting a perf session so it can be cleaned
up properly.

Change-Id: Ie0e4a43f751beb77afdc84e9d52b21780f279d80
Signed-off-by: default avatarNeil Leeder <nleeder@codeaurora.org>
parent fe311197

arch/arm/kernel/perf_event.c

+1 −0
Original line number Diff line number Diff line
@@ -563,6 +563,7 @@ static void armpmu_init(struct arm_pmu *armpmu) 
	armpmu->pmu.start = armpmu_start;

	armpmu->pmu.stop = armpmu_stop;

	armpmu->pmu.read = armpmu_read;

	armpmu->pmu.events_across_hotplug = 1;

}



int armpmu_register(struct arm_pmu *armpmu, int type)

arch/arm/kernel/perf_event_cpu.c

+27 −25
Original line number Diff line number Diff line
@@ -186,6 +186,26 @@ static void disable_irq_callback(void *info) 
	disable_percpu_irq(irq);

}



static void armpmu_update_counters(void)

{

	struct pmu_hw_events *hw_events;

	int idx;



	if (!cpu_pmu)

		return;



	hw_events = cpu_pmu->get_hw_events();



	for (idx = 0; idx <= cpu_pmu->num_events; ++idx) {

		struct perf_event *event = hw_events->events[idx];



		if (!event)

			continue;



		cpu_pmu->pmu.read(event);

	}

}



/*

 * PMU hardware loses all context when a CPU goes offline.

 * When a CPU is hotplugged back in, since some hardware registers are
@@ -196,11 +216,13 @@ static int __cpuinit cpu_pmu_notify(struct notifier_block *b, 
				    unsigned long action, void *hcpu)

{

	int irq;

	struct pmu *pmu;



	if (cpu_has_active_perf((int)hcpu)) {

		switch ((action & ~CPU_TASKS_FROZEN)) {



		case CPU_DOWN_PREPARE:

			armpmu_update_counters();

			/*

			 * If this is on a multicore CPU, we need

			 * to disarm the PMU IRQ before disappearing.
@@ -213,7 +235,7 @@ static int __cpuinit cpu_pmu_notify(struct notifier_block *b, 
			}

			return NOTIFY_DONE;



		case CPU_UP_PREPARE:

		case CPU_STARTING:

			/*

			 * If this is on a multicore CPU, we need

			 * to arm the PMU IRQ before appearing.
@@ -221,14 +243,14 @@ static int __cpuinit cpu_pmu_notify(struct notifier_block *b, 
			if (cpu_pmu &&

				cpu_pmu->plat_device->dev.platform_data) {

				irq = platform_get_irq(cpu_pmu->plat_device, 0);

				smp_call_function_single((int)hcpu,

						enable_irq_callback, &irq, 1);

				enable_irq_callback(&irq);

			}

			return NOTIFY_DONE;



		case CPU_STARTING:

			if (cpu_pmu && cpu_pmu->reset) {

				__get_cpu_var(from_idle) = 1;

				cpu_pmu->reset(NULL);

				pmu = &cpu_pmu->pmu;

				pmu->pmu_enable(pmu);

				return NOTIFY_OK;

			}

		default:
@@ -248,26 +270,6 @@ static struct notifier_block __cpuinitdata cpu_pmu_hotplug_notifier = { 
	.notifier_call = cpu_pmu_notify,

};



static void armpmu_update_counters(void)

{

	struct pmu_hw_events *hw_events;

	int idx;



	if (!cpu_pmu)

		return;



	hw_events = cpu_pmu->get_hw_events();



	for (idx = 0; idx <= cpu_pmu->num_events; ++idx) {

		struct perf_event *event = hw_events->events[idx];



		if (!event)

			continue;



		cpu_pmu->pmu.read(event);

	}

}



/*TODO: Unify with pending patch from ARM */

static int perf_cpu_pm_notifier(struct notifier_block *self, unsigned long cmd,

		void *v)

arch/arm/mach-msm/perf_debug.c

+3 −2
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ 
static char *descriptions =

	" 0 msm: perf: add debug patch logging framework\n"

	" 1 Perf: port perf-events to 3.10 kernel\n"

	" 2 Perf: keep events across hotplug\n"

;



static ssize_t desc_read(struct file *fp, char __user *buf,

include/linux/perf_event.h

+2 −0
Original line number Diff line number Diff line
@@ -194,6 +194,8 @@ struct pmu { 
	int * __percpu			pmu_disable_count;

	struct perf_cpu_context * __percpu pmu_cpu_context;

	int				task_ctx_nr;

	u32                             events_across_hotplug:1,

					reserved:31;



	/*

	 * Fully disable/enable this PMU, can be used to protect from the PMI

kernel/events/core.c

+42 −7
Original line number Diff line number Diff line
@@ -1248,6 +1248,28 @@ static int __perf_remove_from_context(void *info) 
	return 0;

}



#ifdef CONFIG_SMP

static void perf_retry_remove(struct perf_event *event)

{

	int up_ret;

	/*

	 * CPU was offline. Bring it online so we can

	 * gracefully exit a perf context.

	 */

	up_ret = cpu_up(event->cpu);

	if (!up_ret)

		/* Try the remove call once again. */

		cpu_function_call(event->cpu, __perf_remove_from_context,

				  event);

	else

		pr_err("Failed to bring up CPU: %d, ret: %d\n",

		       event->cpu, up_ret);

}

#else

static void perf_retry_remove(struct perf_event *event)

{

}

#endif



/*

 * Remove the event from a task's (or a CPU's) list of events.
@@ -1262,19 +1284,23 @@ static int __perf_remove_from_context(void *info) 
 * When called from perf_event_exit_task, it's OK because the

 * context has been detached from its task.

 */

static void perf_remove_from_context(struct perf_event *event)

static void __ref perf_remove_from_context(struct perf_event *event)

{

	struct perf_event_context *ctx = event->ctx;

	struct task_struct *task = ctx->task;

	int ret;



	lockdep_assert_held(&ctx->mutex);



	if (!task) {

		/*

		 * Per cpu events are removed via an smp call and

		 * the removal is always successful.

		 * Per cpu events are removed via an smp call

		 */

		cpu_function_call(event->cpu, __perf_remove_from_context, event);

		ret = cpu_function_call(event->cpu, __perf_remove_from_context,

					event);

		if (ret == -ENXIO)

			perf_retry_remove(event);

		return;

	}
@@ -7417,12 +7443,21 @@ static void perf_event_exit_cpu_context(int cpu) 


	idx = srcu_read_lock(&pmus_srcu);

	list_for_each_entry_rcu(pmu, &pmus, entry) {

		/*

		 * If keeping events across hotplugging is supported, do not

		 * remove the event list, but keep it alive across CPU hotplug.

		 * The context is exited via an fd close path when userspace

		 * is done and the target CPU is online.

		 */

		if (!pmu->events_across_hotplug) {

			ctx = &per_cpu_ptr(pmu->pmu_cpu_context, cpu)->ctx;



			mutex_lock(&ctx->mutex);

		smp_call_function_single(cpu, __perf_event_exit_context, ctx, 1);

			smp_call_function_single(cpu, __perf_event_exit_context,

						 ctx, 1);

			mutex_unlock(&ctx->mutex);

		}

	}

	srcu_read_unlock(&pmus_srcu, idx);

}