Commit 04289bb9 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

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: default avatarIngo Molnar <mingo@elte.hu>
parent 9f66a381

arch/x86/kernel/cpu/perf_counter.c

+14 −14
Original line number Diff line number Diff line
@@ -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;

		}

include/linux/perf_counter.h

+6 −2
Original line number Diff line number Diff line
@@ -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;

kernel/perf_counter.c

+216 −66
Original line number Diff line number Diff line
@@ -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();
@@ -387,17 +491,24 @@ void perf_counter_task_tick(struct task_struct *curr, int cpu) 
}



/*

 * Initialize the perf_counter context in task_struct

 * Initialize the perf_counter context in a task_struct:

 */

void perf_counter_init_task(struct task_struct *task)

static void

__perf_counter_init_context(struct perf_counter_context *ctx,

			    struct task_struct *task)

{

	struct perf_counter_context *ctx = &task->perf_counter_ctx;



	spin_lock_init(&ctx->lock);

	INIT_LIST_HEAD(&ctx->counters);

	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)

{

	__perf_counter_init_context(&task->perf_counter_ctx, task);

}



/*

 * Cross CPU call to read the hardware counter
@@ -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:

CRA Git | Maintained and supported by SUSTech CRA and CCSE