[RFC][PATCH 14/19] perf: Per-pmu-per-cpu contexts

From: Peter Zijlstra
Date: Tue Sep 07 2010 - 12:57:21 EST

Allocate per-cpu contexts per pmu.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
include/linux/perf_event.h | 4 -
kernel/perf_event.c | 159 +++++++++++++++++++++++++++------------------
2 files changed, 101 insertions(+), 62 deletions(-)

Index: linux-2.6/include/linux/perf_event.h
===================================================================
--- linux-2.6.orig/include/linux/perf_event.h
+++ linux-2.6/include/linux/perf_event.h
@@ -570,7 +570,8 @@ struct perf_event;
struct pmu {
struct list_head entry;

- int *pmu_disable_count;
+ int * __percpu pmu_disable_count;
+ struct perf_cpu_context * __percpu pmu_cpu_context;

/*
* Fully disable/enable this PMU, can be used to protect from the PMI
@@ -813,6 +814,7 @@ struct perf_event {
* Used as a container for task events and CPU events as well:
*/
struct perf_event_context {
+ struct pmu *pmu;
/*
* Protect the states of the events in the list,
* nr_active, and the list:
Index: linux-2.6/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/kernel/perf_event.c
+++ linux-2.6/kernel/perf_event.c
@@ -34,16 +34,15 @@

#include <asm/irq_regs.h>

-/*
- * Each CPU has a list of per CPU events:
- */
-static DEFINE_PER_CPU(struct perf_cpu_context, perf_cpu_context);
-
static atomic_t nr_events __read_mostly;
static atomic_t nr_mmap_events __read_mostly;
static atomic_t nr_comm_events __read_mostly;
static atomic_t nr_task_events __read_mostly;

+static LIST_HEAD(pmus);
+static DEFINE_MUTEX(pmus_lock);
+static struct srcu_struct pmus_srcu;
+
/*
* perf event paranoia level:
* -1 - not paranoid at all
@@ -447,6 +446,12 @@ group_sched_out(struct perf_event *group
cpuctx->exclusive = 0;
}

+static inline struct perf_cpu_context *
+__get_cpu_context(struct perf_event_context *ctx)
+{
+ return this_cpu_ptr(ctx->pmu->pmu_cpu_context);
+}
+
/*
* Cross CPU call to remove a performance event
*
@@ -455,9 +460,9 @@ group_sched_out(struct perf_event *group
*/
static void __perf_event_remove_from_context(void *info)
{
- struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_event *event = info;
struct perf_event_context *ctx = event->ctx;
+ struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

/*
* If this is a task context, we need to check whether it is
@@ -537,8 +542,8 @@ static void perf_event_remove_from_conte
static void __perf_event_disable(void *info)
{
struct perf_event *event = info;
- struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_event_context *ctx = event->ctx;
+ struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

/*
* If this is a per-task event, need to check whether this
@@ -746,10 +751,10 @@ static void add_event_to_ctx(struct perf
*/
static void __perf_install_in_context(void *info)
{
- struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_event *event = info;
struct perf_event_context *ctx = event->ctx;
struct perf_event *leader = event->group_leader;
+ struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
int err;

/*
@@ -893,9 +898,9 @@ static void __perf_event_mark_enabled(st
static void __perf_event_enable(void *info)
{
struct perf_event *event = info;
- struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_event_context *ctx = event->ctx;
struct perf_event *leader = event->group_leader;
+ struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
int err;

/*
@@ -1169,8 +1174,8 @@ static void perf_event_sync_stat(struct
void perf_event_task_sched_out(struct task_struct *task,
struct task_struct *next)
{
- struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_event_context *ctx = task->perf_event_ctxp;
+ struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
struct perf_event_context *next_ctx;
struct perf_event_context *parent;
int do_switch = 1;
@@ -1223,7 +1228,7 @@ void perf_event_task_sched_out(struct ta
static void task_ctx_sched_out(struct perf_event_context *ctx,
enum event_type_t event_type)
{
- struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+ struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

if (!cpuctx->task_ctx)
return;
@@ -1341,8 +1346,8 @@ static void cpu_ctx_sched_in(struct perf
static void task_ctx_sched_in(struct task_struct *task,
enum event_type_t event_type)
{
- struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_event_context *ctx = task->perf_event_ctxp;
+ struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

if (likely(!ctx))
return;
@@ -1364,8 +1369,8 @@ static void task_ctx_sched_in(struct tas
*/
void perf_event_task_sched_in(struct task_struct *task)
{
- struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_event_context *ctx = task->perf_event_ctxp;
+ struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

if (likely(!ctx))
return;
@@ -1593,7 +1598,7 @@ static enum hrtimer_restart perf_event_c

static void perf_pmu_rotate_start(struct pmu *pmu)
{
- struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+ struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);

if (hrtimer_active(&cpuctx->timer))
return;
@@ -1669,9 +1674,9 @@ static void perf_event_enable_on_exec(st
*/
static void __perf_event_read(void *info)
{
- struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_event *event = info;
struct perf_event_context *ctx = event->ctx;
+ struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

/*
* If this is a task context, we need to check whether it is
@@ -1944,7 +1949,8 @@ __perf_event_init_context(struct perf_ev
ctx->task = task;
}

-static struct perf_event_context *find_get_context(pid_t pid, int cpu)
+static struct perf_event_context *
+find_get_context(struct pmu *pmu, pid_t pid, int cpu)
{
struct perf_event_context *ctx;
struct perf_cpu_context *cpuctx;
@@ -1968,7 +1974,7 @@ static struct perf_event_context *find_g
if (!cpu_online(cpu))
return ERR_PTR(-ENODEV);

- cpuctx = &per_cpu(perf_cpu_context, cpu);
+ cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
ctx = &cpuctx->ctx;
get_ctx(ctx);

@@ -2012,6 +2018,7 @@ static struct perf_event_context *find_g
if (!ctx)
goto errout;
__perf_event_init_context(ctx, task);
+ ctx->pmu = pmu;
get_ctx(ctx);
if (cmpxchg(&task->perf_event_ctxp, NULL, ctx)) {
/*
@@ -3727,18 +3734,20 @@ static void perf_event_task_ctx(struct p

static void perf_event_task_event(struct perf_task_event *task_event)
{
- struct perf_cpu_context *cpuctx;
struct perf_event_context *ctx = task_event->task_ctx;
+ struct perf_cpu_context *cpuctx;
+ struct pmu *pmu;

- rcu_read_lock();
- cpuctx = &get_cpu_var(perf_cpu_context);
- perf_event_task_ctx(&cpuctx->ctx, task_event);
+ rcu_read_lock_sched();
+ list_for_each_entry_rcu(pmu, &pmus, entry) {
+ cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
+ perf_event_task_ctx(&cpuctx->ctx, task_event);
+ }
if (!ctx)
ctx = rcu_dereference(current->perf_event_ctxp);
if (ctx)
perf_event_task_ctx(ctx, task_event);
- put_cpu_var(perf_cpu_context);
- rcu_read_unlock();
+ rcu_read_unlock_sched();
}

static void perf_event_task(struct task_struct *task,
@@ -3843,6 +3852,7 @@ static void perf_event_comm_event(struct
struct perf_cpu_context *cpuctx;
struct perf_event_context *ctx;
unsigned int size;
+ struct pmu *pmu;
char comm[TASK_COMM_LEN];

memset(comm, 0, sizeof(comm));
@@ -3854,14 +3864,15 @@ static void perf_event_comm_event(struct

comm_event->event_id.header.size = sizeof(comm_event->event_id) + size;

- rcu_read_lock();
- cpuctx = &get_cpu_var(perf_cpu_context);
- perf_event_comm_ctx(&cpuctx->ctx, comm_event);
+ rcu_read_lock_sched();
+ list_for_each_entry_rcu(pmu, &pmus, entry) {
+ cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
+ perf_event_comm_ctx(&cpuctx->ctx, comm_event);
+ }
ctx = rcu_dereference(current->perf_event_ctxp);
if (ctx)
perf_event_comm_ctx(ctx, comm_event);
- put_cpu_var(perf_cpu_context);
- rcu_read_unlock();
+ rcu_read_unlock_sched();
}

void perf_event_comm(struct task_struct *task)
@@ -3971,6 +3982,7 @@ static void perf_event_mmap_event(struct
char tmp[16];
char *buf = NULL;
const char *name;
+ struct pmu *pmu;

memset(tmp, 0, sizeof(tmp));

@@ -4022,14 +4034,16 @@ static void perf_event_mmap_event(struct

mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size;

- rcu_read_lock();
- cpuctx = &get_cpu_var(perf_cpu_context);
- perf_event_mmap_ctx(&cpuctx->ctx, mmap_event, vma->vm_flags & VM_EXEC);
+ rcu_read_lock_sched();
+ list_for_each_entry_rcu(pmu, &pmus, entry) {
+ cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
+ perf_event_mmap_ctx(&cpuctx->ctx, mmap_event,
+ vma->vm_flags & VM_EXEC);
+ }
ctx = rcu_dereference(current->perf_event_ctxp);
if (ctx)
perf_event_mmap_ctx(ctx, mmap_event, vma->vm_flags & VM_EXEC);
- put_cpu_var(perf_cpu_context);
- rcu_read_unlock();
+ rcu_read_unlock_sched();

kfree(buf);
}
@@ -4964,10 +4978,6 @@ static struct pmu perf_task_clock = {
.read = task_clock_event_read,
};

-static LIST_HEAD(pmus);
-static DEFINE_MUTEX(pmus_lock);
-static struct srcu_struct pmus_srcu;
-
static void perf_pmu_nop_void(struct pmu *pmu)
{
}
@@ -4995,7 +5005,7 @@ static void perf_pmu_cancel_txn(struct p

int perf_pmu_register(struct pmu *pmu)
{
- int ret;
+ int cpu, ret;

mutex_lock(&pmus_lock);
ret = -ENOMEM;
@@ -5003,6 +5013,21 @@ int perf_pmu_register(struct pmu *pmu)
if (!pmu->pmu_disable_count)
goto unlock;

+ pmu->pmu_cpu_context = alloc_percpu(struct perf_cpu_context);
+ if (!pmu->pmu_cpu_context)
+ goto free_pdc;
+
+ for_each_possible_cpu(cpu) {
+ struct perf_cpu_context *cpuctx;
+
+ cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
+ __perf_event_init_context(&cpuctx->ctx, NULL);
+ cpuctx->ctx.pmu = pmu;
+ cpuctx->timer_interval = TICK_NSEC;
+ hrtimer_init(&cpuctx->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ cpuctx->timer.function = perf_event_context_tick;
+ }
+
if (!pmu->start_txn) {
if (pmu->pmu_enable) {
/*
@@ -5034,6 +5059,10 @@ int perf_pmu_register(struct pmu *pmu)
mutex_unlock(&pmus_lock);

return ret;
+
+free_pdc:
+ free_percpu(pmu->pmu_disable_count);
+ goto unlock;
}

void perf_pmu_unregister(struct pmu *pmu)
@@ -5042,9 +5071,14 @@ void perf_pmu_unregister(struct pmu *pmu
list_del_rcu(&pmu->entry);
mutex_unlock(&pmus_lock);

+ /*
+ * We use the pmu list either under SRCU or preempt_disable,
+ * synchronize_srcu() implies synchronize_sched() so we're good.
+ */
synchronize_srcu(&pmus_srcu);

free_percpu(pmu->pmu_disable_count);
+ free_percpu(pmu->pmu_cpu_context);
}

struct pmu *perf_init_event(struct perf_event *event)
@@ -5359,7 +5393,7 @@ SYSCALL_DEFINE5(perf_event_open,
/*
* Get the target context (task or percpu):
*/
- ctx = find_get_context(pid, cpu);
+ ctx = find_get_context(event->pmu, pid, cpu);
if (IS_ERR(ctx)) {
err = PTR_ERR(ctx);
goto err_alloc;
@@ -5474,7 +5508,7 @@ perf_event_create_kernel_counter(struct
goto err;
}

- ctx = find_get_context(pid, cpu);
+ ctx = find_get_context(event->pmu, pid, cpu);
if (IS_ERR(ctx)) {
err = PTR_ERR(ctx);
goto err_free;
@@ -5818,6 +5852,7 @@ inherit_task_group(struct perf_event *ev
return -ENOMEM;

__perf_event_init_context(child_ctx, child);
+ child_ctx->pmu = event->pmu;
child->perf_event_ctxp = child_ctx;
get_task_struct(child);
}
@@ -5920,30 +5955,18 @@ int perf_event_init_task(struct task_str

static void __init perf_event_init_all_cpus(void)
{
- struct perf_cpu_context *cpuctx;
struct swevent_htable *swhash;
int cpu;

for_each_possible_cpu(cpu) {
swhash = &per_cpu(swevent_htable, cpu);
mutex_init(&swhash->hlist_mutex);
-
- cpuctx = &per_cpu(perf_cpu_context, cpu);
- __perf_event_init_context(&cpuctx->ctx, NULL);
- cpuctx->timer_interval = TICK_NSEC;
- hrtimer_init(&cpuctx->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
- cpuctx->timer.function = perf_event_context_tick;
}
}

static void __cpuinit perf_event_init_cpu(int cpu)
{
- struct perf_cpu_context *cpuctx;
- struct swevent_htable *swhash;
-
- cpuctx = &per_cpu(perf_cpu_context, cpu);
-
- swhash = &per_cpu(swevent_htable, cpu);
+ struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);

mutex_lock(&swhash->hlist_mutex);
if (swhash->hlist_refcount > 0) {
@@ -5957,10 +5980,9 @@ static void __cpuinit perf_event_init_cp
}

#ifdef CONFIG_HOTPLUG_CPU
-static void __perf_event_exit_cpu(void *info)
+static void __perf_event_exit_context(void *__info)
{
- struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
- struct perf_event_context *ctx = &cpuctx->ctx;
+ struct perf_event_context *ctx = __info;
struct perf_event *event, *tmp;

list_for_each_entry_safe(event, tmp, &ctx->pinned_groups, group_entry)
@@ -5968,19 +5990,34 @@ static void __perf_event_exit_cpu(void *
list_for_each_entry_safe(event, tmp, &ctx->flexible_groups, group_entry)
__perf_event_remove_from_context(event);
}
+
+static void perf_event_exit_cpu_context(int cpu)
+{
+ struct perf_event_context *ctx;
+ struct pmu *pmu;
+ int idx;
+
+ idx = srcu_read_lock(&pmus_srcu);
+ list_for_each_entry_rcu(pmu, &pmus, entry) {
+ ctx = &this_cpu_ptr(pmu->pmu_cpu_context)->ctx;
+
+ 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);
+
+}
+
static void perf_event_exit_cpu(int cpu)
{
- struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);
- struct perf_event_context *ctx = &cpuctx->ctx;

mutex_lock(&swhash->hlist_mutex);
swevent_hlist_release(swhash);
mutex_unlock(&swhash->hlist_mutex);

- mutex_lock(&ctx->mutex);
- smp_call_function_single(cpu, __perf_event_exit_cpu, NULL, 1);
- mutex_unlock(&ctx->mutex);
+ perf_event_exit_cpu_context(cpu);
}
#else
static inline void perf_event_exit_cpu(int cpu) { }


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