blender/intern/cycles/util/util_task.cpp

/*
 * Copyright 2011-2013 Blender Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "util/util_debug.h"
#include "util/util_foreach.h"
#include "util/util_logging.h"
#include "util/util_system.h"
#include "util/util_task.h"
#include "util/util_time.h"

//#define THREADING_DEBUG_ENABLED

#ifdef THREADING_DEBUG_ENABLED
#include <stdio.h>
#define THREADING_DEBUG(...) do { printf(__VA_ARGS__); fflush(stdout); } while(0)
#else
#define THREADING_DEBUG(...)
#endif

CCL_NAMESPACE_BEGIN

/* Task Pool */

TaskPool::TaskPool()
{
	num_tasks_handled = 0;
	num = 0;
	do_cancel = false;
}

TaskPool::~TaskPool()
{
	stop();
}

void TaskPool::push(Task *task, bool front)
{
	TaskScheduler::Entry entry;

	entry.task = task;
	entry.pool = this;

	TaskScheduler::push(entry, front);
}

void TaskPool::push(const TaskRunFunction& run, bool front)
{
	push(new Task(run), front);
}

void TaskPool::wait_work(Summary *stats)
{
	thread_scoped_lock num_lock(num_mutex);

	while(num != 0) {
		num_lock.unlock();

		thread_scoped_lock queue_lock(TaskScheduler::queue_mutex);

		/* find task from this pool. if we get a task from another pool,
		 * we can get into deadlock */
		TaskScheduler::Entry work_entry;
		bool found_entry = false;
		list<TaskScheduler::Entry>::iterator it;

		for(it = TaskScheduler::queue.begin(); it != TaskScheduler::queue.end(); it++) {
			TaskScheduler::Entry& entry = *it;

			if(entry.pool == this) {
				work_entry = entry;
				found_entry = true;
				TaskScheduler::queue.erase(it);
				break;
			}
		}

		queue_lock.unlock();

		/* if found task, do it, otherwise wait until other tasks are done */
		if(found_entry) {
			/* run task */
			work_entry.task->run(0);

			/* delete task */
			delete work_entry.task;

			/* notify pool task was done */
			num_decrease(1);
		}

		num_lock.lock();
		if(num == 0)
			break;

		if(!found_entry) {
			THREADING_DEBUG("num==%d, Waiting for condition in TaskPool::wait_work !found_entry\n", num);
			num_cond.wait(num_lock);
			THREADING_DEBUG("num==%d, condition wait done in TaskPool::wait_work !found_entry\n", num);
		}
	}

	if(stats != NULL) {
		stats->time_total = time_dt() - start_time;
		stats->num_tasks_handled = num_tasks_handled;
	}
}

void TaskPool::cancel()
{
	do_cancel = true;

	TaskScheduler::clear(this);
	
	{
		thread_scoped_lock num_lock(num_mutex);

		while(num) {
			THREADING_DEBUG("num==%d, Waiting for condition in TaskPool::cancel\n", num);
			num_cond.wait(num_lock);
			THREADING_DEBUG("num==%d condition wait done in TaskPool::cancel\n", num);
		}
	}

	do_cancel = false;
}

void TaskPool::stop()
{
	TaskScheduler::clear(this);

	assert(num == 0);
}

bool TaskPool::canceled()
{
	return do_cancel;
}

void TaskPool::num_decrease(int done)
{
	num_mutex.lock();
	num -= done;

	assert(num >= 0);
	if(num == 0) {
		THREADING_DEBUG("num==%d, notifying all in TaskPool::num_decrease\n", num);
		num_cond.notify_all();
	}

	num_mutex.unlock();
}

void TaskPool::num_increase()
{
	thread_scoped_lock num_lock(num_mutex);
	if(num_tasks_handled == 0) {
		start_time = time_dt();
	}
	num++;
	num_tasks_handled++;
	THREADING_DEBUG("num==%d, notifying all in TaskPool::num_increase\n", num);
	num_cond.notify_all();
}

/* Task Scheduler */

thread_mutex TaskScheduler::mutex;
int TaskScheduler::users = 0;
vector<thread*> TaskScheduler::threads;
bool TaskScheduler::do_exit = false;

list<TaskScheduler::Entry> TaskScheduler::queue;
thread_mutex TaskScheduler::queue_mutex;
thread_condition_variable TaskScheduler::queue_cond;

void TaskScheduler::init(int num_threads)
{
	thread_scoped_lock lock(mutex);

	/* multiple cycles instances can use this task scheduler, sharing the same
	 * threads, so we keep track of the number of users. */
	if(users == 0) {
		do_exit = false;

		const bool use_auto_threads = (num_threads == 0);
		if(use_auto_threads) {
			/* automatic number of threads */
			num_threads = system_cpu_thread_count();
		}
		VLOG(1) << "Creating pool of " << num_threads << " threads.";

		/* launch threads that will be waiting for work */
		threads.resize(num_threads);

		const int num_groups = system_cpu_group_count();
		unsigned short num_process_groups;
		vector<unsigned short> process_groups;
		int current_group_threads;
		if(num_groups > 1) {
			process_groups.resize(num_groups);
			num_process_groups = system_cpu_process_groups(num_groups, 
			                                               &process_groups[0]);
			if(num_process_groups == 1) {
				current_group_threads = system_cpu_group_thread_count(process_groups[0]);
			}
		}
		int thread_index = 0;
		for(int group = 0; group < num_groups; ++group) {
			/* NOTE: That's not really efficient from threading point of view,
			 * but it is simple to read and it doesn't make sense to use more
			 * user-specified threads than logical threads anyway.
			 */
			int num_group_threads = (group == num_groups - 1)
			        ? (threads.size() - thread_index)
			        : system_cpu_group_thread_count(group);
			for(int group_thread = 0;
				group_thread < num_group_threads && thread_index < threads.size();
				++group_thread, ++thread_index)
			{
				/* NOTE: Thread group of -1 means we would not force thread affinity. */
				int thread_group;
				if(num_groups == 1) {
					/* Use default affinity if there's only one CPU group in the system. */
					thread_group = -1;
				}
				else if(use_auto_threads &&
				        num_process_groups == 1 &&
						num_threads <= current_group_threads)
				{
					/* If we fit into curent CPU group we also don't force any affinity. */
					thread_group = -1;
				}
				else {
					thread_group = group;
				}
				threads[thread_index] = new thread(function_bind(&TaskScheduler::thread_run,
				                                                 thread_index + 1),
				                                   thread_group);
			}
		}
	}
	
	users++;
}

void TaskScheduler::exit()
{
	thread_scoped_lock lock(mutex);

	users--;

	if(users == 0) {
		/* stop all waiting threads */
		TaskScheduler::queue_mutex.lock();
		do_exit = true;
		TaskScheduler::queue_cond.notify_all();
		TaskScheduler::queue_mutex.unlock();

		/* delete threads */
		foreach(thread *t, threads) {
			t->join();
			delete t;
		}

		threads.clear();
	}
}

void TaskScheduler::free_memory()
{
	assert(users == 0);
	threads.free_memory();
}

bool TaskScheduler::thread_wait_pop(Entry& entry)
{
	thread_scoped_lock queue_lock(queue_mutex);

	while(queue.empty() && !do_exit)
		queue_cond.wait(queue_lock);

	if(queue.empty()) {
		assert(do_exit);
		return false;
	}
	
	entry = queue.front();
	queue.pop_front();

	return true;
}

void TaskScheduler::thread_run(int thread_id)
{
	Entry entry;

	/* todo: test affinity/denormal mask */

	/* keep popping off tasks */
	while(thread_wait_pop(entry)) {
		/* run task */
		entry.task->run(thread_id);

		/* delete task */
		delete entry.task;

		/* notify pool task was done */
		entry.pool->num_decrease(1);
	}
}

void TaskScheduler::push(Entry& entry, bool front)
{
	entry.pool->num_increase();

	/* add entry to queue */
	TaskScheduler::queue_mutex.lock();
	if(front)
		TaskScheduler::queue.push_front(entry);
	else
		TaskScheduler::queue.push_back(entry);

	TaskScheduler::queue_cond.notify_one();
	TaskScheduler::queue_mutex.unlock();
}

void TaskScheduler::clear(TaskPool *pool)
{
	thread_scoped_lock queue_lock(TaskScheduler::queue_mutex);

	/* erase all tasks from this pool from the queue */
	list<Entry>::iterator it = queue.begin();
	int done = 0;

	while(it != queue.end()) {
		Entry& entry = *it;

		if(entry.pool == pool) {
			done++;
			delete entry.task;

			it = queue.erase(it);
		}
		else
			it++;
	}

	queue_lock.unlock();

	/* notify done */
	pool->num_decrease(done);
}

/* Dedicated Task Pool */

DedicatedTaskPool::DedicatedTaskPool()
{
	do_cancel = false;
	do_exit = false;
	num = 0;

	worker_thread = new thread(function_bind(&DedicatedTaskPool::thread_run, this));
}

DedicatedTaskPool::~DedicatedTaskPool()
{
	stop();
	worker_thread->join();
	delete worker_thread;
}

void DedicatedTaskPool::push(Task *task, bool front)
{
	num_increase();

	/* add task to queue */
	queue_mutex.lock();
	if(front)
		queue.push_front(task);
	else
		queue.push_back(task);

	queue_cond.notify_one();
	queue_mutex.unlock();
}

void DedicatedTaskPool::push(const TaskRunFunction& run, bool front)
{
	push(new Task(run), front);
}

void DedicatedTaskPool::wait()
{
	thread_scoped_lock num_lock(num_mutex);

	while(num)
		num_cond.wait(num_lock);
}

void DedicatedTaskPool::cancel()
{
	do_cancel = true;

	clear();
	wait();

	do_cancel = false;
}

void DedicatedTaskPool::stop()
{
	clear();

	do_exit = true;
	queue_cond.notify_all();

	wait();

	assert(num == 0);
}

bool DedicatedTaskPool::canceled()
{
	return do_cancel;
}

void DedicatedTaskPool::num_decrease(int done)
{
	thread_scoped_lock num_lock(num_mutex);
	num -= done;

	assert(num >= 0);
	if(num == 0)
		num_cond.notify_all();
}

void DedicatedTaskPool::num_increase()
{
	thread_scoped_lock num_lock(num_mutex);
	num++;
	num_cond.notify_all();
}

bool DedicatedTaskPool::thread_wait_pop(Task*& task)
{
	thread_scoped_lock queue_lock(queue_mutex);

	while(queue.empty() && !do_exit)
		queue_cond.wait(queue_lock);

	if(queue.empty()) {
		assert(do_exit);
		return false;
	}

	task = queue.front();
	queue.pop_front();

	return true;
}

void DedicatedTaskPool::thread_run()
{
	Task *task;

	/* keep popping off tasks */
	while(thread_wait_pop(task)) {
		/* run task */
		task->run(0);

		/* delete task */
		delete task;

		/* notify task was done */
		num_decrease(1);
	}
}

void DedicatedTaskPool::clear()
{
	thread_scoped_lock queue_lock(queue_mutex);

	/* erase all tasks from the queue */
	list<Task*>::iterator it = queue.begin();
	int done = 0;

	while(it != queue.end()) {
		done++;
		delete *it;

		it = queue.erase(it);
	}

	queue_lock.unlock();

	/* notify done */
	num_decrease(done);
}

string TaskPool::Summary::full_report() const
{
	string report = "";
	report += string_printf("Total time:    %f\n", time_total);
	report += string_printf("Tasks handled: %d\n", num_tasks_handled);
	return report;
}

CCL_NAMESPACE_END