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Perf: keep events across hotplug

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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: Neil Leeder <nleeder@codeaurora.org>
This commit is contained in:
Neil Leeder
2013-11-13 09:12:09 -08:00
committed by Gerrit - the friendly Code Review server
parent 1b3051eaac
commit 8a64588190
4 changed files with 104 additions and 64 deletions
Download Patch File Download Diff File Expand all files Collapse all files
arch/arm/kernel/perf_event.c
+59 -56
View File
@@ -716,6 +716,7 @@ 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, char *name, int type)
@@ -826,62 +827,6 @@ static int cpu_has_active_perf(int cpu)
return 0;
}
/*
* PMU hardware loses all context when a CPU goes offline.
* When a CPU is hotplugged back in, since some hardware registers are
* UNKNOWN at reset, the PMU must be explicitly reset to avoid reading
* junk values out of them.
*/
static int __cpuinit pmu_cpu_notify(struct notifier_block *b,
unsigned long action, void *hcpu)
{
int irq;
if (cpu_has_active_perf((int)hcpu)) {
switch ((action & ~CPU_TASKS_FROZEN)) {
case CPU_DOWN_PREPARE:
/*
* If this is on a multicore CPU, we need
* to disarm the PMU IRQ before disappearing.
*/
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,
disable_irq_callback, &irq, 1);
}
return NOTIFY_DONE;
case CPU_UP_PREPARE:
/*
* If this is on a multicore CPU, we need
* to arm the PMU IRQ before appearing.
*/
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);
}
return NOTIFY_DONE;
case CPU_STARTING:
if (cpu_pmu && cpu_pmu->reset) {
cpu_pmu->reset(NULL);
return NOTIFY_OK;
}
default:
return NOTIFY_DONE;
}
}
if ((action & ~CPU_TASKS_FROZEN) != CPU_STARTING)
return NOTIFY_DONE;
return NOTIFY_OK;
}
static void armpmu_update_counters(void)
{
struct pmu_hw_events *hw_events;
@@ -902,6 +847,64 @@ static void armpmu_update_counters(void)
}
}
/*
* PMU hardware loses all context when a CPU goes offline.
* When a CPU is hotplugged back in, since some hardware registers are
* UNKNOWN at reset, the PMU must be explicitly reset to avoid reading
* junk values out of them.
*/
static int __cpuinit pmu_cpu_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.
*/
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,
disable_irq_callback, &irq, 1);
}
return NOTIFY_DONE;
case CPU_STARTING:
/*
* If this is on a multicore CPU, we need
* to arm the PMU IRQ before appearing.
*/
if (cpu_pmu &&
cpu_pmu->plat_device->dev.platform_data) {
irq = platform_get_irq(cpu_pmu->plat_device, 0);
enable_irq_callback(&irq);
}
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:
return NOTIFY_DONE;
}
}
if ((action & ~CPU_TASKS_FROZEN) != CPU_STARTING)
return NOTIFY_DONE;
return NOTIFY_OK;
}
static struct notifier_block __cpuinitdata pmu_cpu_notifier = {
.notifier_call = pmu_cpu_notify,
};
arch/arm/mach-msm/perf_debug.c
+1
View File
@@ -36,6 +36,7 @@ static char *descriptions =
"11 ARM: dts: msm: add perf-events support for msm8x10, msm8x12\n"
"12 Perf: Make per-process counters configurable\n"
"13 msm: perf: Add L2 support for tracecounters\n"
"14 Perf: keep events across hotplug\n"
;
static ssize_t desc_read(struct file *fp, char __user *buf,
include/linux/perf_event.h
+2
View File
@@ -740,6 +740,8 @@ 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 -8
View File
@@ -1194,6 +1194,28 @@ 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.
@@ -1208,19 +1230,22 @@ 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;
}
@@ -7029,11 +7054,20 @@ static void perf_event_exit_cpu_context(int cpu)
idx = srcu_read_lock(&pmus_srcu);
list_for_each_entry_rcu(pmu, &pmus, entry) {
ctx = &per_cpu_ptr(pmu->pmu_cpu_context, cpu)->ctx;
/*
* 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);
mutex_unlock(&ctx->mutex);
mutex_lock(&ctx->mutex);
smp_call_function_single(cpu, __perf_event_exit_context,
ctx, 1);
mutex_unlock(&ctx->mutex);
}
}
srcu_read_unlock(&pmus_srcu, idx);
}