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perf counters: add support for group counters 

Impact: add group counters

This patch adds the "counter groups" abstraction.

Groups of counters behave much like normal 'single' counters, with a
few semantic and behavioral extensions on top of that.

A counter group is created by creating a new counter with the open()
syscall's group-leader group_fd file descriptor parameter pointing
to another, already existing counter.

Groups of counters are scheduled in and out in one atomic group, and
they are also roundrobin-scheduled atomically.

Counters that are member of a group can also record events with an
(atomic) extended timestamp that extends to all members of the group,
if the record type is set to PERF_RECORD_GROUP.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Ingo Molnar 2008-12-11 08:38:42 +01:00
parent 9f66a3810f
commit 04289bb989
3 changed files with 236 additions and 82 deletions
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28
arch/x86/kernel/cpu/perf_counter.c
View File

@ -346,18 +346,22 @@ static void perf_save_and_restart(struct perf_counter *counter)
}
static void
perf_handle_group(struct perf_counter *leader, u64 *status, u64 *overflown)
perf_handle_group(struct perf_counter *sibling, u64 *status, u64 *overflown)
{
struct perf_counter_context *ctx = leader->ctx;
struct perf_counter *counter;
struct perf_counter *counter, *group_leader = sibling->group_leader;
int bit;
list_for_each_entry(counter, &ctx->counters, list) {
if (counter->hw_event.record_type != PERF_RECORD_SIMPLE ||
counter == leader)
continue;
/*
* Store the counter's own timestamp first:
*/
perf_store_irq_data(sibling, sibling->hw_event.type);
perf_store_irq_data(sibling, atomic64_counter_read(sibling));
if (counter->active) {
/*
* Then store sibling timestamps (if any):
*/
list_for_each_entry(counter, &group_leader->sibling_list, list_entry) {
if (!counter->active) {
/*
* When counter was not in the overflow mask, we have to
* read it from hardware. We read it as well, when it
@ -371,8 +375,8 @@ perf_handle_group(struct perf_counter *leader, u64 *status, u64 *overflown)
perf_save_and_restart(counter);
}
}
perf_store_irq_data(leader, counter->hw_event.type);
perf_store_irq_data(leader, atomic64_counter_read(counter));
perf_store_irq_data(sibling, counter->hw_event.type);
perf_store_irq_data(sibling, atomic64_counter_read(counter));
}
}
@ -416,10 +420,6 @@ again:
perf_store_irq_data(counter, instruction_pointer(regs));
break;
case PERF_RECORD_GROUP:
perf_store_irq_data(counter,
counter->hw_event.type);
perf_store_irq_data(counter,
atomic64_counter_read(counter));
perf_handle_group(counter, &status, &ack);
break;
}

8
include/linux/perf_counter.h
View File

@ -117,7 +117,10 @@ struct perf_data {
* struct perf_counter - performance counter kernel representation:
*/
struct perf_counter {
struct list_head list;
struct list_head list_entry;
struct list_head sibling_list;
struct perf_counter *group_leader;
int active;
#if BITS_PER_LONG == 64
atomic64_t count;
@ -158,7 +161,8 @@ struct perf_counter_context {
* Protect the list of counters:
*/
spinlock_t lock;
struct list_head counters;
struct list_head counter_list;
int nr_counters;
int nr_active;
struct task_struct *task;

282
kernel/perf_counter.c
View File

@ -10,6 +10,7 @@
#include <linux/fs.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <linux/file.h>
#include <linux/poll.h>
#include <linux/sysfs.h>
#include <linux/ptrace.h>
@ -55,7 +56,7 @@ void __weak hw_perf_counter_setup(void) { }
* Read the cached counter in counter safe against cross CPU / NMI
* modifications. 64 bit version - no complications.
*/
static inline u64 perf_read_counter_safe(struct perf_counter *counter)
static inline u64 perf_counter_read_safe(struct perf_counter *counter)
{
return (u64) atomic64_read(&counter->count);
}
@ -66,7 +67,7 @@ static inline u64 perf_read_counter_safe(struct perf_counter *counter)
* Read the cached counter in counter safe against cross CPU / NMI
* modifications. 32 bit version.
*/
static u64 perf_read_counter_safe(struct perf_counter *counter)
static u64 perf_counter_read_safe(struct perf_counter *counter)
{
u32 cntl, cnth;
@ -83,13 +84,55 @@ static u64 perf_read_counter_safe(struct perf_counter *counter)
#endif
static void
list_add_counter(struct perf_counter *counter, struct perf_counter_context *ctx)
{
struct perf_counter *group_leader = counter->group_leader;
/*
* Depending on whether it is a standalone or sibling counter,
* add it straight to the context's counter list, or to the group
* leader's sibling list:
*/
if (counter->group_leader == counter)
list_add_tail(&counter->list_entry, &ctx->counter_list);
else
list_add_tail(&counter->list_entry, &group_leader->sibling_list);
}
static void
list_del_counter(struct perf_counter *counter, struct perf_counter_context *ctx)
{
struct perf_counter *sibling, *tmp;
list_del_init(&counter->list_entry);
if (list_empty(&counter->sibling_list))
return;
/*
* If this was a group counter with sibling counters then
* upgrade the siblings to singleton counters by adding them
* to the context list directly:
*/
list_for_each_entry_safe(sibling, tmp,
&counter->sibling_list, list_entry) {
list_del_init(&sibling->list_entry);
list_add_tail(&sibling->list_entry, &ctx->counter_list);
WARN_ON_ONCE(!sibling->group_leader);
WARN_ON_ONCE(sibling->group_leader == sibling);
sibling->group_leader = sibling;
}
}
/*
* Cross CPU call to remove a performance counter
*
* We disable the counter on the hardware level first. After that we
* remove it from the context list.
*/
static void __perf_remove_from_context(void *info)
static void __perf_counter_remove_from_context(void *info)
{
struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_counter *counter = info;
@ -119,7 +162,7 @@ static void __perf_remove_from_context(void *info)
* counters on a global level. NOP for non NMI based counters.
*/
hw_perf_disable_all();
list_del_init(&counter->list);
list_del_counter(counter, ctx);
hw_perf_enable_all();
if (!ctx->task) {
@ -144,7 +187,7 @@ static void __perf_remove_from_context(void *info)
* CPU counters are removed with a smp call. For task counters we only
* call when the task is on a CPU.
*/
static void perf_remove_from_context(struct perf_counter *counter)
static void perf_counter_remove_from_context(struct perf_counter *counter)
{
struct perf_counter_context *ctx = counter->ctx;
struct task_struct *task = ctx->task;
@ -155,32 +198,32 @@ static void perf_remove_from_context(struct perf_counter *counter)
* the removal is always sucessful.
*/
smp_call_function_single(counter->cpu,
__perf_remove_from_context,
__perf_counter_remove_from_context,
counter, 1);
return;
}
retry:
task_oncpu_function_call(task, __perf_remove_from_context,
task_oncpu_function_call(task, __perf_counter_remove_from_context,
counter);
spin_lock_irq(&ctx->lock);
/*
* If the context is active we need to retry the smp call.
*/
if (ctx->nr_active && !list_empty(&counter->list)) {
if (ctx->nr_active && !list_empty(&counter->list_entry)) {
spin_unlock_irq(&ctx->lock);
goto retry;
}
/*
* The lock prevents that this context is scheduled in so we
* can remove the counter safely, if it the call above did not
* can remove the counter safely, if the call above did not
* succeed.
*/
if (!list_empty(&counter->list)) {
if (!list_empty(&counter->list_entry)) {
ctx->nr_counters--;
list_del_init(&counter->list);
list_del_counter(counter, ctx);
counter->task = NULL;
}
spin_unlock_irq(&ctx->lock);
@ -211,7 +254,7 @@ static void __perf_install_in_context(void *info)
* counters on a global level. NOP for non NMI based counters.
*/
hw_perf_disable_all();
list_add_tail(&counter->list, &ctx->counters);
list_add_counter(counter, ctx);
hw_perf_enable_all();
ctx->nr_counters++;
@ -268,7 +311,7 @@ retry:
* If the context is active and the counter has not been added
* we need to retry the smp call.
*/
if (ctx->nr_active && list_empty(&counter->list)) {
if (ctx->nr_active && list_empty(&counter->list_entry)) {
spin_unlock_irq(&ctx->lock);
goto retry;
}
@ -278,13 +321,45 @@ retry:
* can add the counter safely, if it the call above did not
* succeed.
*/
if (list_empty(&counter->list)) {
list_add_tail(&counter->list, &ctx->counters);
if (list_empty(&counter->list_entry)) {
list_add_counter(counter, ctx);
ctx->nr_counters++;
}
spin_unlock_irq(&ctx->lock);
}
static void
counter_sched_out(struct perf_counter *counter,
struct perf_cpu_context *cpuctx,
struct perf_counter_context *ctx)
{
if (!counter->active)
return;
hw_perf_counter_disable(counter);
counter->active = 0;
counter->oncpu = -1;
cpuctx->active_oncpu--;
ctx->nr_active--;
}
static void
group_sched_out(struct perf_counter *group_counter,
struct perf_cpu_context *cpuctx,
struct perf_counter_context *ctx)
{
struct perf_counter *counter;
counter_sched_out(group_counter, cpuctx, ctx);
/*
* Schedule out siblings (if any):
*/
list_for_each_entry(counter, &group_counter->sibling_list, list_entry)
counter_sched_out(counter, cpuctx, ctx);
}
/*
* Called from scheduler to remove the counters of the current task,
* with interrupts disabled.
@ -306,21 +381,48 @@ void perf_counter_task_sched_out(struct task_struct *task, int cpu)
return;
spin_lock(&ctx->lock);
list_for_each_entry(counter, &ctx->counters, list) {
if (!ctx->nr_active)
break;
if (counter->active) {
hw_perf_counter_disable(counter);
counter->active = 0;
counter->oncpu = -1;
ctx->nr_active--;
cpuctx->active_oncpu--;
}
if (ctx->nr_active) {
list_for_each_entry(counter, &ctx->counter_list, list_entry)
group_sched_out(counter, cpuctx, ctx);
}
spin_unlock(&ctx->lock);
cpuctx->task_ctx = NULL;
}
static void
counter_sched_in(struct perf_counter *counter,
struct perf_cpu_context *cpuctx,
struct perf_counter_context *ctx,
int cpu)
{
if (!counter->active)
return;
hw_perf_counter_enable(counter);
counter->active = 1;
counter->oncpu = cpu; /* TODO: put 'cpu' into cpuctx->cpu */
cpuctx->active_oncpu++;
ctx->nr_active++;
}
static void
group_sched_in(struct perf_counter *group_counter,
struct perf_cpu_context *cpuctx,
struct perf_counter_context *ctx,
int cpu)
{
struct perf_counter *counter;
counter_sched_in(group_counter, cpuctx, ctx, cpu);
/*
* Schedule in siblings as one group (if any):
*/
list_for_each_entry(counter, &group_counter->sibling_list, list_entry)
counter_sched_in(counter, cpuctx, ctx, cpu);
}
/*
* Called from scheduler to add the counters of the current task
* with interrupts disabled.
@ -342,19 +444,21 @@ void perf_counter_task_sched_in(struct task_struct *task, int cpu)
return;
spin_lock(&ctx->lock);
list_for_each_entry(counter, &ctx->counters, list) {
list_for_each_entry(counter, &ctx->counter_list, list_entry) {
if (ctx->nr_active == cpuctx->max_pertask)
break;
/*
* Listen to the 'cpu' scheduling filter constraint
* of counters:
*/
if (counter->cpu != -1 && counter->cpu != cpu)
continue;
hw_perf_counter_enable(counter);
counter->active = 1;
counter->oncpu = cpu;
ctx->nr_active++;
cpuctx->active_oncpu++;
group_sched_in(counter, cpuctx, ctx, cpu);
}
spin_unlock(&ctx->lock);
cpuctx->task_ctx = ctx;
}
@ -371,12 +475,12 @@ void perf_counter_task_tick(struct task_struct *curr, int cpu)
spin_lock(&ctx->lock);
/*
* Rotate the first entry last:
* Rotate the first entry last (works just fine for group counters too):
*/
hw_perf_disable_all();
list_for_each_entry(counter, &ctx->counters, list) {
list_del(&counter->list);
list_add_tail(&counter->list, &ctx->counters);
list_for_each_entry(counter, &ctx->counter_list, list_entry) {
list_del(&counter->list_entry);
list_add_tail(&counter->list_entry, &ctx->counter_list);
break;
}
hw_perf_enable_all();
@ -386,17 +490,24 @@ void perf_counter_task_tick(struct task_struct *curr, int cpu)
perf_counter_task_sched_in(curr, cpu);
}
/*
* Initialize the perf_counter context in a task_struct:
*/
static void
__perf_counter_init_context(struct perf_counter_context *ctx,
struct task_struct *task)
{
spin_lock_init(&ctx->lock);
INIT_LIST_HEAD(&ctx->counter_list);
ctx->nr_counters = 0;
ctx->task = task;
}
/*
* Initialize the perf_counter context in task_struct
*/
void perf_counter_init_task(struct task_struct *task)
{
struct perf_counter_context *ctx = &task->perf_counter_ctx;
spin_lock_init(&ctx->lock);
INIT_LIST_HEAD(&ctx->counters);
ctx->nr_counters = 0;
ctx->task = task;
__perf_counter_init_context(&task->perf_counter_ctx, task);
}
/*
@ -407,7 +518,7 @@ static void __hw_perf_counter_read(void *info)
hw_perf_counter_read(info);
}
static u64 perf_read_counter(struct perf_counter *counter)
static u64 perf_counter_read(struct perf_counter *counter)
{
/*
* If counter is enabled and currently active on a CPU, update the
@ -418,7 +529,7 @@ static u64 perf_read_counter(struct perf_counter *counter)
__hw_perf_counter_read, counter, 1);
}
return perf_read_counter_safe(counter);
return perf_counter_read_safe(counter);
}
/*
@ -555,7 +666,7 @@ static int perf_release(struct inode *inode, struct file *file)
mutex_lock(&counter->mutex);
perf_remove_from_context(counter);
perf_counter_remove_from_context(counter);
put_context(ctx);
mutex_unlock(&counter->mutex);
@ -577,7 +688,7 @@ perf_read_hw(struct perf_counter *counter, char __user *buf, size_t count)
return -EINVAL;
mutex_lock(&counter->mutex);
cntval = perf_read_counter(counter);
cntval = perf_counter_read(counter);
mutex_unlock(&counter->mutex);
return put_user(cntval, (u64 __user *) buf) ? -EFAULT : sizeof(cntval);
@ -707,15 +818,25 @@ static const struct file_operations perf_fops = {
* Allocate and initialize a counter structure
*/
static struct perf_counter *
perf_counter_alloc(struct perf_counter_hw_event *hw_event, int cpu)
perf_counter_alloc(struct perf_counter_hw_event *hw_event,
int cpu,
struct perf_counter *group_leader)
{
struct perf_counter *counter = kzalloc(sizeof(*counter), GFP_KERNEL);
if (!counter)
return NULL;
/*
* Single counters are their own group leaders, with an
* empty sibling list:
*/
if (!group_leader)
group_leader = counter;
mutex_init(&counter->mutex);
INIT_LIST_HEAD(&counter->list);
INIT_LIST_HEAD(&counter->list_entry);
INIT_LIST_HEAD(&counter->sibling_list);
init_waitqueue_head(&counter->waitq);
counter->irqdata = &counter->data[0];
@ -723,6 +844,7 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event, int cpu)
counter->cpu = cpu;
counter->hw_event = *hw_event;
counter->wakeup_pending = 0;
counter->group_leader = group_leader;
return counter;
}
@ -743,20 +865,45 @@ asmlinkage int sys_perf_counter_open(
int group_fd)
{
struct perf_counter_context *ctx;
struct perf_counter *counter, *group_leader;
struct perf_counter_hw_event hw_event;
struct perf_counter *counter;
struct perf_counter_context *ctx;
struct file *group_file = NULL;
int fput_needed = 0;
int ret;
if (copy_from_user(&hw_event, hw_event_uptr, sizeof(hw_event)) != 0)
return -EFAULT;
/*
* Look up the group leader:
*/
group_leader = NULL;
if (group_fd != -1) {
ret = -EINVAL;
group_file = fget_light(group_fd, &fput_needed);
if (!group_file)
goto out_fput;
if (group_file->f_op != &perf_fops)
goto out_fput;
group_leader = group_file->private_data;
/*
* Do not allow a recursive hierarchy:
*/
if (group_leader->group_leader)
goto out_fput;
}
/*
* Get the target context (task or percpu):
*/
ctx = find_get_context(pid, cpu);
if (IS_ERR(ctx))
return PTR_ERR(ctx);
ret = -ENOMEM;
counter = perf_counter_alloc(&hw_event, cpu);
counter = perf_counter_alloc(&hw_event, cpu, group_leader);
if (!counter)
goto err_put_context;
@ -770,11 +917,14 @@ asmlinkage int sys_perf_counter_open(
if (ret < 0)
goto err_remove_free_put_context;
out_fput:
fput_light(group_file, fput_needed);
return ret;
err_remove_free_put_context:
mutex_lock(&counter->mutex);
perf_remove_from_context(counter);
perf_counter_remove_from_context(counter);
mutex_unlock(&counter->mutex);
err_free_put_context:
@ -783,40 +933,40 @@ err_free_put_context:
err_put_context:
put_context(ctx);
return ret;
goto out_fput;
}
static void __cpuinit perf_init_cpu(int cpu)
static void __cpuinit perf_counter_init_cpu(int cpu)
{
struct perf_cpu_context *ctx;
struct perf_cpu_context *cpuctx;
ctx = &per_cpu(perf_cpu_context, cpu);
spin_lock_init(&ctx->ctx.lock);
INIT_LIST_HEAD(&ctx->ctx.counters);
cpuctx = &per_cpu(perf_cpu_context, cpu);
__perf_counter_init_context(&cpuctx->ctx, NULL);
mutex_lock(&perf_resource_mutex);
ctx->max_pertask = perf_max_counters - perf_reserved_percpu;
cpuctx->max_pertask = perf_max_counters - perf_reserved_percpu;
mutex_unlock(&perf_resource_mutex);
hw_perf_counter_setup();
}
#ifdef CONFIG_HOTPLUG_CPU
static void __perf_exit_cpu(void *info)
static void __perf_counter_exit_cpu(void *info)
{
struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_counter_context *ctx = &cpuctx->ctx;
struct perf_counter *counter, *tmp;
list_for_each_entry_safe(counter, tmp, &ctx->counters, list)
__perf_remove_from_context(counter);
list_for_each_entry_safe(counter, tmp, &ctx->counter_list, list_entry)
__perf_counter_remove_from_context(counter);
}
static void perf_exit_cpu(int cpu)
static void perf_counter_exit_cpu(int cpu)
{
smp_call_function_single(cpu, __perf_exit_cpu, NULL, 1);
smp_call_function_single(cpu, __perf_counter_exit_cpu, NULL, 1);
}
#else
static inline void perf_exit_cpu(int cpu) { }
static inline void perf_counter_exit_cpu(int cpu) { }
#endif
static int __cpuinit
@ -828,12 +978,12 @@ perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
perf_init_cpu(cpu);
perf_counter_init_cpu(cpu);
break;
case CPU_DOWN_PREPARE:
case CPU_DOWN_PREPARE_FROZEN:
perf_exit_cpu(cpu);
perf_counter_exit_cpu(cpu);
break;
default: