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|
/*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
/** \file
* \ingroup bli
*
* A generic task system which can be used for any task based subsystem.
*/
#include <stdlib.h>
#include "MEM_guardedalloc.h"
#include "DNA_listBase.h"
#include "BLI_listbase.h"
#include "BLI_math.h"
#include "BLI_mempool.h"
#include "BLI_task.h"
#include "BLI_threads.h"
#include "atomic_ops.h"
/* Define this to enable some detailed statistic print. */
#undef DEBUG_STATS
/* Types */
/* Number of per-thread pre-allocated tasks.
*
* For more details see description of TaskMemPool.
*/
#define MEMPOOL_SIZE 256
/* Number of tasks which are pushed directly to local thread queue.
*
* This allows thread to fetch next task without locking the whole queue.
*/
#define LOCAL_QUEUE_SIZE 1
/* Number of tasks which are allowed to be scheduled in a delayed manner.
*
* This allows to use less locks per graph node children schedule. More details
* could be found at TaskThreadLocalStorage::do_delayed_push.
*/
#define DELAYED_QUEUE_SIZE 4096
#ifndef NDEBUG
# define ASSERT_THREAD_ID(scheduler, thread_id) \
do { \
if (!BLI_thread_is_main()) { \
TaskThread *thread = pthread_getspecific(scheduler->tls_id_key); \
if (thread == NULL) { \
BLI_assert(thread_id == 0); \
} \
else { \
BLI_assert(thread_id == thread->id); \
} \
} \
else { \
BLI_assert(thread_id == 0); \
} \
} while (false)
#else
# define ASSERT_THREAD_ID(scheduler, thread_id)
#endif
typedef struct Task {
struct Task *next, *prev;
TaskRunFunction run;
void *taskdata;
bool free_taskdata;
TaskFreeFunction freedata;
TaskPool *pool;
} Task;
/* This is a per-thread storage of pre-allocated tasks.
*
* The idea behind this is simple: reduce amount of malloc() calls when pushing
* new task to the pool. This is done by keeping memory from the tasks which
* were finished already, so instead of freeing that memory we put it to the
* pool for the later re-use.
*
* The tricky part here is to avoid any inter-thread synchronization, hence no
* lock must exist around this pool. The pool will become an owner of the pointer
* from freed task, and only corresponding thread will be able to use this pool
* (no memory stealing and such).
*
* This leads to the following use of the pool:
*
* - task_push() should provide proper thread ID from which the task is being
* pushed from.
*
* - Task allocation function which check corresponding memory pool and if there
* is any memory in there it'll mark memory as re-used, remove it from the pool
* and use that memory for the new task.
*
* At this moment task queue owns the memory.
*
* - When task is done and task_free() is called the memory will be put to the
* pool which corresponds to a thread which handled the task.
*/
typedef struct TaskMemPool {
/* Number of pre-allocated tasks in the pool. */
int num_tasks;
/* Pre-allocated task memory pointers. */
Task *tasks[MEMPOOL_SIZE];
} TaskMemPool;
#ifdef DEBUG_STATS
typedef struct TaskMemPoolStats {
/* Number of allocations. */
int num_alloc;
/* Number of avoided allocations (pointer was re-used from the pool). */
int num_reuse;
/* Number of discarded memory due to pool saturation, */
int num_discard;
} TaskMemPoolStats;
#endif
typedef struct TaskThreadLocalStorage {
/* Memory pool for faster task allocation.
* The idea is to re-use memory of finished/discarded tasks by this thread.
*/
TaskMemPool task_mempool;
/* Local queue keeps thread alive by keeping small amount of tasks ready
* to be picked up without causing global thread locks for synchronization.
*/
int num_local_queue;
Task *local_queue[LOCAL_QUEUE_SIZE];
/* Thread can be marked for delayed tasks push. This is helpful when it's
* know that lots of subsequent task pushed will happen from the same thread
* without "interrupting" for task execution.
*
* We try to accumulate as much tasks as possible in a local queue without
* any locks first, and then we push all of them into a schedulers queue
* from within a single mutex lock.
*/
bool do_delayed_push;
int num_delayed_queue;
Task *delayed_queue[DELAYED_QUEUE_SIZE];
} TaskThreadLocalStorage;
struct TaskPool {
TaskScheduler *scheduler;
volatile size_t num;
ThreadMutex num_mutex;
ThreadCondition num_cond;
void *userdata;
ThreadMutex user_mutex;
volatile bool do_cancel;
volatile bool do_work;
volatile bool is_suspended;
bool start_suspended;
ListBase suspended_queue;
size_t num_suspended;
/* If set, this pool may never be work_and_wait'ed, which means TaskScheduler
* has to use its special background fallback thread in case we are in
* single-threaded situation.
*/
bool run_in_background;
/* This is a task scheduler's ID of a thread at which pool was constructed.
* It will be used to access task TLS.
*/
int thread_id;
/* For the pools which are created from non-main thread which is not a
* scheduler worker thread we can't re-use any of scheduler's threads TLS
* and have to use our own one.
*/
bool use_local_tls;
TaskThreadLocalStorage local_tls;
#ifndef NDEBUG
pthread_t creator_thread_id;
#endif
#ifdef DEBUG_STATS
TaskMemPoolStats *mempool_stats;
#endif
};
struct TaskScheduler {
pthread_t *threads;
struct TaskThread *task_threads;
int num_threads;
bool background_thread_only;
ListBase queue;
ThreadMutex queue_mutex;
ThreadCondition queue_cond;
ThreadMutex startup_mutex;
ThreadCondition startup_cond;
volatile int num_thread_started;
volatile bool do_exit;
/* NOTE: In pthread's TLS we store the whole TaskThread structure. */
pthread_key_t tls_id_key;
};
typedef struct TaskThread {
TaskScheduler *scheduler;
int id;
TaskThreadLocalStorage tls;
} TaskThread;
/* Helper */
BLI_INLINE void task_data_free(Task *task, const int thread_id)
{
if (task->free_taskdata) {
if (task->freedata) {
task->freedata(task->pool, task->taskdata, thread_id);
}
else {
MEM_freeN(task->taskdata);
}
}
}
BLI_INLINE void initialize_task_tls(TaskThreadLocalStorage *tls)
{
memset(tls, 0, sizeof(TaskThreadLocalStorage));
}
BLI_INLINE TaskThreadLocalStorage *get_task_tls(TaskPool *pool, const int thread_id)
{
TaskScheduler *scheduler = pool->scheduler;
BLI_assert(thread_id >= 0);
BLI_assert(thread_id <= scheduler->num_threads);
if (pool->use_local_tls && thread_id == 0) {
BLI_assert(pool->thread_id == 0);
BLI_assert(!BLI_thread_is_main());
BLI_assert(pthread_equal(pthread_self(), pool->creator_thread_id));
return &pool->local_tls;
}
if (thread_id == 0) {
BLI_assert(BLI_thread_is_main());
return &scheduler->task_threads[pool->thread_id].tls;
}
return &scheduler->task_threads[thread_id].tls;
}
BLI_INLINE void free_task_tls(TaskThreadLocalStorage *tls)
{
TaskMemPool *task_mempool = &tls->task_mempool;
for (int i = 0; i < task_mempool->num_tasks; i++) {
MEM_freeN(task_mempool->tasks[i]);
}
}
static Task *task_alloc(TaskPool *pool, const int thread_id)
{
BLI_assert(thread_id <= pool->scheduler->num_threads);
if (thread_id != -1) {
BLI_assert(thread_id >= 0);
BLI_assert(thread_id <= pool->scheduler->num_threads);
TaskThreadLocalStorage *tls = get_task_tls(pool, thread_id);
TaskMemPool *task_mempool = &tls->task_mempool;
/* Try to re-use task memory from a thread local storage. */
if (task_mempool->num_tasks > 0) {
--task_mempool->num_tasks;
/* Success! We've just avoided task allocation. */
#ifdef DEBUG_STATS
pool->mempool_stats[thread_id].num_reuse++;
#endif
return task_mempool->tasks[task_mempool->num_tasks];
}
/* We are doomed to allocate new task data. */
#ifdef DEBUG_STATS
pool->mempool_stats[thread_id].num_alloc++;
#endif
}
return MEM_mallocN(sizeof(Task), "New task");
}
static void task_free(TaskPool *pool, Task *task, const int thread_id)
{
task_data_free(task, thread_id);
BLI_assert(thread_id >= 0);
BLI_assert(thread_id <= pool->scheduler->num_threads);
if (thread_id == 0) {
BLI_assert(pool->use_local_tls || BLI_thread_is_main());
}
TaskThreadLocalStorage *tls = get_task_tls(pool, thread_id);
TaskMemPool *task_mempool = &tls->task_mempool;
if (task_mempool->num_tasks < MEMPOOL_SIZE - 1) {
/* Successfully allowed the task to be re-used later. */
task_mempool->tasks[task_mempool->num_tasks] = task;
++task_mempool->num_tasks;
}
else {
/* Local storage saturated, no other way than just discard
* the memory.
*
* TODO(sergey): We can perhaps store such pointer in a global
* scheduler pool, maybe it'll be faster than discarding and
* allocating again.
*/
MEM_freeN(task);
#ifdef DEBUG_STATS
pool->mempool_stats[thread_id].num_discard++;
#endif
}
}
/* Task Scheduler */
static void task_pool_num_decrease(TaskPool *pool, size_t done)
{
BLI_mutex_lock(&pool->num_mutex);
BLI_assert(pool->num >= done);
pool->num -= done;
if (pool->num == 0) {
BLI_condition_notify_all(&pool->num_cond);
}
BLI_mutex_unlock(&pool->num_mutex);
}
static void task_pool_num_increase(TaskPool *pool, size_t new)
{
BLI_mutex_lock(&pool->num_mutex);
pool->num += new;
BLI_condition_notify_all(&pool->num_cond);
BLI_mutex_unlock(&pool->num_mutex);
}
static bool task_scheduler_thread_wait_pop(TaskScheduler *scheduler, Task **task)
{
bool found_task = false;
BLI_mutex_lock(&scheduler->queue_mutex);
while (!scheduler->queue.first && !scheduler->do_exit) {
BLI_condition_wait(&scheduler->queue_cond, &scheduler->queue_mutex);
}
do {
Task *current_task;
/* Assuming we can only have a void queue in 'exit' case here seems logical
* (we should only be here after our worker thread has been woken up from a
* condition_wait(), which only happens after a new task was added to the queue),
* but it is wrong.
* Waiting on condition may wake up the thread even if condition is not signaled
* (spurious wake-ups), and some race condition may also empty the queue **after**
* condition has been signaled, but **before** awoken thread reaches this point...
* See http://stackoverflow.com/questions/8594591
*
* So we only abort here if do_exit is set.
*/
if (scheduler->do_exit) {
BLI_mutex_unlock(&scheduler->queue_mutex);
return false;
}
for (current_task = scheduler->queue.first; current_task != NULL;
current_task = current_task->next) {
TaskPool *pool = current_task->pool;
if (scheduler->background_thread_only && !pool->run_in_background) {
continue;
}
*task = current_task;
found_task = true;
BLI_remlink(&scheduler->queue, *task);
break;
}
if (!found_task) {
BLI_condition_wait(&scheduler->queue_cond, &scheduler->queue_mutex);
}
} while (!found_task);
BLI_mutex_unlock(&scheduler->queue_mutex);
return true;
}
BLI_INLINE void handle_local_queue(TaskThreadLocalStorage *tls, const int thread_id)
{
BLI_assert(!tls->do_delayed_push);
while (tls->num_local_queue > 0) {
/* We pop task from queue before handling it so handler of the task can
* push next job to the local queue.
*/
tls->num_local_queue--;
Task *local_task = tls->local_queue[tls->num_local_queue];
/* TODO(sergey): Double-check work_and_wait() doesn't handle other's
* pool tasks.
*/
TaskPool *local_pool = local_task->pool;
local_task->run(local_pool, local_task->taskdata, thread_id);
task_free(local_pool, local_task, thread_id);
}
BLI_assert(!tls->do_delayed_push);
}
static void *task_scheduler_thread_run(void *thread_p)
{
TaskThread *thread = (TaskThread *)thread_p;
TaskThreadLocalStorage *tls = &thread->tls;
TaskScheduler *scheduler = thread->scheduler;
int thread_id = thread->id;
Task *task;
pthread_setspecific(scheduler->tls_id_key, thread);
/* signal the main thread when all threads have started */
BLI_mutex_lock(&scheduler->startup_mutex);
scheduler->num_thread_started++;
if (scheduler->num_thread_started == scheduler->num_threads) {
BLI_condition_notify_one(&scheduler->startup_cond);
}
BLI_mutex_unlock(&scheduler->startup_mutex);
/* keep popping off tasks */
while (task_scheduler_thread_wait_pop(scheduler, &task)) {
TaskPool *pool = task->pool;
/* run task */
BLI_assert(!tls->do_delayed_push);
task->run(pool, task->taskdata, thread_id);
BLI_assert(!tls->do_delayed_push);
/* delete task */
task_free(pool, task, thread_id);
/* Handle all tasks from local queue. */
handle_local_queue(tls, thread_id);
/* notify pool task was done */
task_pool_num_decrease(pool, 1);
}
return NULL;
}
TaskScheduler *BLI_task_scheduler_create(int num_threads)
{
TaskScheduler *scheduler = MEM_callocN(sizeof(TaskScheduler), "TaskScheduler");
/* multiple places can use this task scheduler, sharing the same
* threads, so we keep track of the number of users. */
scheduler->do_exit = false;
BLI_listbase_clear(&scheduler->queue);
BLI_mutex_init(&scheduler->queue_mutex);
BLI_condition_init(&scheduler->queue_cond);
BLI_mutex_init(&scheduler->startup_mutex);
BLI_condition_init(&scheduler->startup_cond);
scheduler->num_thread_started = 0;
if (num_threads == 0) {
/* automatic number of threads will be main thread + num cores */
num_threads = BLI_system_thread_count();
}
/* main thread will also work, so we count it too */
num_threads -= 1;
/* Add background-only thread if needed. */
if (num_threads == 0) {
scheduler->background_thread_only = true;
num_threads = 1;
}
scheduler->task_threads = MEM_mallocN(sizeof(TaskThread) * (num_threads + 1),
"TaskScheduler task threads");
/* Initialize TLS for main thread. */
initialize_task_tls(&scheduler->task_threads[0].tls);
pthread_key_create(&scheduler->tls_id_key, NULL);
/* launch threads that will be waiting for work */
if (num_threads > 0) {
int i;
scheduler->num_threads = num_threads;
scheduler->threads = MEM_callocN(sizeof(pthread_t) * num_threads, "TaskScheduler threads");
for (i = 0; i < num_threads; i++) {
TaskThread *thread = &scheduler->task_threads[i + 1];
thread->scheduler = scheduler;
thread->id = i + 1;
initialize_task_tls(&thread->tls);
if (pthread_create(&scheduler->threads[i], NULL, task_scheduler_thread_run, thread) != 0) {
fprintf(stderr, "TaskScheduler failed to launch thread %d/%d\n", i, num_threads);
}
}
}
/* Wait for all worker threads to start before returning to caller to prevent the case where
* threads are still starting and pthread_join is called, which causes a deadlock on pthreads4w.
*/
BLI_mutex_lock(&scheduler->startup_mutex);
/* NOTE: Use loop here to avoid false-positive everything-is-ready caused by spontaneous thread
* wake up. */
while (scheduler->num_thread_started != num_threads) {
BLI_condition_wait(&scheduler->startup_cond, &scheduler->startup_mutex);
}
BLI_mutex_unlock(&scheduler->startup_mutex);
return scheduler;
}
void BLI_task_scheduler_free(TaskScheduler *scheduler)
{
Task *task;
/* stop all waiting threads */
BLI_mutex_lock(&scheduler->queue_mutex);
scheduler->do_exit = true;
BLI_condition_notify_all(&scheduler->queue_cond);
BLI_mutex_unlock(&scheduler->queue_mutex);
pthread_key_delete(scheduler->tls_id_key);
/* delete threads */
if (scheduler->threads) {
int i;
for (i = 0; i < scheduler->num_threads; i++) {
if (pthread_join(scheduler->threads[i], NULL) != 0) {
fprintf(stderr, "TaskScheduler failed to join thread %d/%d\n", i, scheduler->num_threads);
}
}
MEM_freeN(scheduler->threads);
}
/* Delete task thread data */
if (scheduler->task_threads) {
for (int i = 0; i < scheduler->num_threads + 1; i++) {
TaskThreadLocalStorage *tls = &scheduler->task_threads[i].tls;
free_task_tls(tls);
}
MEM_freeN(scheduler->task_threads);
}
/* delete leftover tasks */
for (task = scheduler->queue.first; task; task = task->next) {
task_data_free(task, 0);
}
BLI_freelistN(&scheduler->queue);
/* delete mutex/condition */
BLI_mutex_end(&scheduler->queue_mutex);
BLI_condition_end(&scheduler->queue_cond);
BLI_mutex_end(&scheduler->startup_mutex);
BLI_condition_end(&scheduler->startup_cond);
MEM_freeN(scheduler);
}
int BLI_task_scheduler_num_threads(TaskScheduler *scheduler)
{
return scheduler->num_threads + 1;
}
static void task_scheduler_push(TaskScheduler *scheduler, Task *task, TaskPriority priority)
{
task_pool_num_increase(task->pool, 1);
/* add task to queue */
BLI_mutex_lock(&scheduler->queue_mutex);
if (priority == TASK_PRIORITY_HIGH) {
BLI_addhead(&scheduler->queue, task);
}
else {
BLI_addtail(&scheduler->queue, task);
}
BLI_condition_notify_one(&scheduler->queue_cond);
BLI_mutex_unlock(&scheduler->queue_mutex);
}
static void task_scheduler_push_all(TaskScheduler *scheduler,
TaskPool *pool,
Task **tasks,
int num_tasks)
{
if (num_tasks == 0) {
return;
}
task_pool_num_increase(pool, num_tasks);
BLI_mutex_lock(&scheduler->queue_mutex);
for (int i = 0; i < num_tasks; i++) {
BLI_addhead(&scheduler->queue, tasks[i]);
}
BLI_condition_notify_all(&scheduler->queue_cond);
BLI_mutex_unlock(&scheduler->queue_mutex);
}
static void task_scheduler_clear(TaskScheduler *scheduler, TaskPool *pool)
{
Task *task, *nexttask;
size_t done = 0;
BLI_mutex_lock(&scheduler->queue_mutex);
/* free all tasks from this pool from the queue */
for (task = scheduler->queue.first; task; task = nexttask) {
nexttask = task->next;
if (task->pool == pool) {
task_data_free(task, pool->thread_id);
BLI_freelinkN(&scheduler->queue, task);
done++;
}
}
BLI_mutex_unlock(&scheduler->queue_mutex);
/* notify done */
task_pool_num_decrease(pool, done);
}
/* Task Pool */
static TaskPool *task_pool_create_ex(TaskScheduler *scheduler,
void *userdata,
const bool is_background,
const bool is_suspended)
{
TaskPool *pool = MEM_mallocN(sizeof(TaskPool), "TaskPool");
#ifndef NDEBUG
/* Assert we do not try to create a background pool from some parent task -
* those only work OK from main thread. */
if (is_background) {
const pthread_t thread_id = pthread_self();
int i = scheduler->num_threads;
while (i--) {
BLI_assert(!pthread_equal(scheduler->threads[i], thread_id));
}
}
#endif
pool->scheduler = scheduler;
pool->num = 0;
pool->do_cancel = false;
pool->do_work = false;
pool->is_suspended = is_suspended;
pool->start_suspended = is_suspended;
pool->num_suspended = 0;
pool->suspended_queue.first = pool->suspended_queue.last = NULL;
pool->run_in_background = is_background;
pool->use_local_tls = false;
BLI_mutex_init(&pool->num_mutex);
BLI_condition_init(&pool->num_cond);
pool->userdata = userdata;
BLI_mutex_init(&pool->user_mutex);
if (BLI_thread_is_main()) {
pool->thread_id = 0;
}
else {
TaskThread *thread = pthread_getspecific(scheduler->tls_id_key);
if (thread == NULL) {
/* NOTE: Task pool is created from non-main thread which is not
* managed by the task scheduler. We identify ourselves as thread ID
* 0 but we do not use scheduler's TLS storage and use our own
* instead to avoid any possible threading conflicts.
*/
pool->thread_id = 0;
pool->use_local_tls = true;
#ifndef NDEBUG
pool->creator_thread_id = pthread_self();
#endif
initialize_task_tls(&pool->local_tls);
}
else {
pool->thread_id = thread->id;
}
}
#ifdef DEBUG_STATS
pool->mempool_stats = MEM_callocN(sizeof(*pool->mempool_stats) * (scheduler->num_threads + 1),
"per-taskpool mempool stats");
#endif
/* Ensure malloc will go fine from threads,
*
* This is needed because we could be in main thread here
* and malloc could be non-thread safe at this point because
* no other jobs are running.
*/
BLI_threaded_malloc_begin();
return pool;
}
/**
* Create a normal task pool. Tasks will be executed as soon as they are added.
*/
TaskPool *BLI_task_pool_create(TaskScheduler *scheduler, void *userdata)
{
return task_pool_create_ex(scheduler, userdata, false, false);
}
/**
* Create a background task pool.
* In multi-threaded context, there is no differences with #BLI_task_pool_create(),
* but in single-threaded case it is ensured to have at least one worker thread to run on
* (i.e. you don't have to call #BLI_task_pool_work_and_wait
* on it to be sure it will be processed).
*
* \note Background pools are non-recursive
* (that is, you should not create other background pools in tasks assigned to a background pool,
* they could end never being executed, since the 'fallback' background thread is already
* busy with parent task in single-threaded context).
*/
TaskPool *BLI_task_pool_create_background(TaskScheduler *scheduler, void *userdata)
{
return task_pool_create_ex(scheduler, userdata, true, false);
}
/**
* Similar to BLI_task_pool_create() but does not schedule any tasks for execution
* for until BLI_task_pool_work_and_wait() is called. This helps reducing threading
* overhead when pushing huge amount of small initial tasks from the main thread.
*/
TaskPool *BLI_task_pool_create_suspended(TaskScheduler *scheduler, void *userdata)
{
return task_pool_create_ex(scheduler, userdata, false, true);
}
void BLI_task_pool_free(TaskPool *pool)
{
BLI_task_pool_cancel(pool);
BLI_mutex_end(&pool->num_mutex);
BLI_condition_end(&pool->num_cond);
BLI_mutex_end(&pool->user_mutex);
#ifdef DEBUG_STATS
printf("Thread ID Allocated Reused Discarded\n");
for (int i = 0; i < pool->scheduler->num_threads + 1; i++) {
printf("%02d %05d %05d %05d\n",
i,
pool->mempool_stats[i].num_alloc,
pool->mempool_stats[i].num_reuse,
pool->mempool_stats[i].num_discard);
}
MEM_freeN(pool->mempool_stats);
#endif
if (pool->use_local_tls) {
free_task_tls(&pool->local_tls);
}
MEM_freeN(pool);
BLI_threaded_malloc_end();
}
BLI_INLINE bool task_can_use_local_queues(TaskPool *pool, int thread_id)
{
return (thread_id != -1 && (thread_id != pool->thread_id || pool->do_work));
}
static void task_pool_push(TaskPool *pool,
TaskRunFunction run,
void *taskdata,
bool free_taskdata,
TaskFreeFunction freedata,
TaskPriority priority,
int thread_id)
{
/* Allocate task and fill it's properties. */
Task *task = task_alloc(pool, thread_id);
task->run = run;
task->taskdata = taskdata;
task->free_taskdata = free_taskdata;
task->freedata = freedata;
task->pool = pool;
/* For suspended pools we put everything yo a global queue first
* and exit as soon as possible.
*
* This tasks will be moved to actual execution when pool is
* activated by work_and_wait().
*/
if (pool->is_suspended) {
BLI_addhead(&pool->suspended_queue, task);
atomic_fetch_and_add_z(&pool->num_suspended, 1);
return;
}
/* Populate to any local queue first, this is cheapest push ever. */
if (task_can_use_local_queues(pool, thread_id)) {
ASSERT_THREAD_ID(pool->scheduler, thread_id);
TaskThreadLocalStorage *tls = get_task_tls(pool, thread_id);
/* Try to push to a local execution queue.
* These tasks will be picked up next.
*/
if (tls->num_local_queue < LOCAL_QUEUE_SIZE) {
tls->local_queue[tls->num_local_queue] = task;
tls->num_local_queue++;
return;
}
/* If we are in the delayed tasks push mode, we push tasks to a
* temporary local queue first without any locks, and then move them
* to global execution queue with a single lock.
*/
if (tls->do_delayed_push && tls->num_delayed_queue < DELAYED_QUEUE_SIZE) {
tls->delayed_queue[tls->num_delayed_queue] = task;
tls->num_delayed_queue++;
return;
}
}
/* Do push to a global execution pool, slowest possible method,
* causes quite reasonable amount of threading overhead.
*/
task_scheduler_push(pool->scheduler, task, priority);
}
void BLI_task_pool_push_ex(TaskPool *pool,
TaskRunFunction run,
void *taskdata,
bool free_taskdata,
TaskFreeFunction freedata,
TaskPriority priority)
{
task_pool_push(pool, run, taskdata, free_taskdata, freedata, priority, -1);
}
void BLI_task_pool_push(
TaskPool *pool, TaskRunFunction run, void *taskdata, bool free_taskdata, TaskPriority priority)
{
BLI_task_pool_push_ex(pool, run, taskdata, free_taskdata, NULL, priority);
}
void BLI_task_pool_push_from_thread(TaskPool *pool,
TaskRunFunction run,
void *taskdata,
bool free_taskdata,
TaskPriority priority,
int thread_id)
{
task_pool_push(pool, run, taskdata, free_taskdata, NULL, priority, thread_id);
}
void BLI_task_pool_work_and_wait(TaskPool *pool)
{
TaskThreadLocalStorage *tls = get_task_tls(pool, pool->thread_id);
TaskScheduler *scheduler = pool->scheduler;
if (atomic_fetch_and_and_uint8((uint8_t *)&pool->is_suspended, 0)) {
if (pool->num_suspended) {
task_pool_num_increase(pool, pool->num_suspended);
BLI_mutex_lock(&scheduler->queue_mutex);
BLI_movelisttolist(&scheduler->queue, &pool->suspended_queue);
BLI_condition_notify_all(&scheduler->queue_cond);
BLI_mutex_unlock(&scheduler->queue_mutex);
pool->num_suspended = 0;
}
}
pool->do_work = true;
ASSERT_THREAD_ID(pool->scheduler, pool->thread_id);
handle_local_queue(tls, pool->thread_id);
BLI_mutex_lock(&pool->num_mutex);
while (pool->num != 0) {
Task *task, *work_task = NULL;
bool found_task = false;
BLI_mutex_unlock(&pool->num_mutex);
BLI_mutex_lock(&scheduler->queue_mutex);
/* find task from this pool. if we get a task from another pool,
* we can get into deadlock */
for (task = scheduler->queue.first; task; task = task->next) {
if (task->pool == pool) {
work_task = task;
found_task = true;
BLI_remlink(&scheduler->queue, task);
break;
}
}
BLI_mutex_unlock(&scheduler->queue_mutex);
/* if found task, do it, otherwise wait until other tasks are done */
if (found_task) {
/* run task */
BLI_assert(!tls->do_delayed_push);
work_task->run(pool, work_task->taskdata, pool->thread_id);
BLI_assert(!tls->do_delayed_push);
/* delete task */
task_free(pool, task, pool->thread_id);
/* Handle all tasks from local queue. */
handle_local_queue(tls, pool->thread_id);
/* notify pool task was done */
task_pool_num_decrease(pool, 1);
}
BLI_mutex_lock(&pool->num_mutex);
if (pool->num == 0) {
break;
}
if (!found_task) {
BLI_condition_wait(&pool->num_cond, &pool->num_mutex);
}
}
BLI_mutex_unlock(&pool->num_mutex);
BLI_assert(tls->num_local_queue == 0);
}
void BLI_task_pool_work_wait_and_reset(TaskPool *pool)
{
BLI_task_pool_work_and_wait(pool);
pool->do_work = false;
pool->is_suspended = pool->start_suspended;
}
void BLI_task_pool_cancel(TaskPool *pool)
{
pool->do_cancel = true;
task_scheduler_clear(pool->scheduler, pool);
/* wait until all entries are cleared */
BLI_mutex_lock(&pool->num_mutex);
while (pool->num) {
BLI_condition_wait(&pool->num_cond, &pool->num_mutex);
}
BLI_mutex_unlock(&pool->num_mutex);
pool->do_cancel = false;
}
bool BLI_task_pool_canceled(TaskPool *pool)
{
return pool->do_cancel;
}
void *BLI_task_pool_userdata(TaskPool *pool)
{
return pool->userdata;
}
ThreadMutex *BLI_task_pool_user_mutex(TaskPool *pool)
{
return &pool->user_mutex;
}
void BLI_task_pool_delayed_push_begin(TaskPool *pool, int thread_id)
{
if (task_can_use_local_queues(pool, thread_id)) {
ASSERT_THREAD_ID(pool->scheduler, thread_id);
TaskThreadLocalStorage *tls = get_task_tls(pool, thread_id);
tls->do_delayed_push = true;
}
}
void BLI_task_pool_delayed_push_end(TaskPool *pool, int thread_id)
{
if (task_can_use_local_queues(pool, thread_id)) {
ASSERT_THREAD_ID(pool->scheduler, thread_id);
TaskThreadLocalStorage *tls = get_task_tls(pool, thread_id);
BLI_assert(tls->do_delayed_push);
task_scheduler_push_all(pool->scheduler, pool, tls->delayed_queue, tls->num_delayed_queue);
tls->do_delayed_push = false;
tls->num_delayed_queue = 0;
}
}
/* Parallel range routines */
/**
*
* Main functions:
* - #BLI_task_parallel_range
* - #BLI_task_parallel_listbase (#ListBase - double linked list)
*
* TODO:
* - #BLI_task_parallel_foreach_link (#Link - single linked list)
* - #BLI_task_parallel_foreach_ghash/gset (#GHash/#GSet - hash & set)
* - #BLI_task_parallel_foreach_mempool (#BLI_mempool - iterate over mempools)
*/
/* Allows to avoid using malloc for userdata_chunk in tasks, when small enough. */
#define MALLOCA(_size) ((_size) <= 8192) ? alloca((_size)) : MEM_mallocN((_size), __func__)
#define MALLOCA_FREE(_mem, _size) \
if (((_mem) != NULL) && ((_size) > 8192)) \
MEM_freeN((_mem))
typedef struct ParallelRangeState {
int start, stop;
void *userdata;
TaskParallelRangeFunc func;
int iter;
int chunk_size;
} ParallelRangeState;
BLI_INLINE void task_parallel_range_calc_chunk_size(const TaskParallelSettings *settings,
const int num_tasks,
ParallelRangeState *state)
{
const int tot_items = state->stop - state->start;
int chunk_size = 0;
if (settings->min_iter_per_thread > 0) {
/* Already set by user, no need to do anything here. */
chunk_size = settings->min_iter_per_thread;
}
else {
/* Multiplier used in heuristics below to define "optimal" chunk size.
* The idea here is to increase the chunk size to compensate for a rather measurable threading
* overhead caused by fetching tasks. With too many CPU threads we are starting
* to spend too much time in those overheads.
* First values are: 1 if num_tasks < 16;
* else 2 if num_tasks < 32;
* else 3 if num_tasks < 48;
* else 4 if num_tasks < 64;
* etc.
* Note: If we wanted to keep the 'power of two' multiplier, we'd need something like:
* 1 << max_ii(0, (int)(sizeof(int) * 8) - 1 - bitscan_reverse_i(num_tasks) - 3)
*/
const int num_tasks_factor = max_ii(1, num_tasks >> 3);
/* We could make that 'base' 32 number configurable in TaskParallelSettings too, or maybe just
* always use that heuristic using TaskParallelSettings.min_iter_per_thread as basis? */
chunk_size = 32 * num_tasks_factor;
/* Basic heuristic to avoid threading on low amount of items.
* We could make that limit configurable in settings too. */
if (tot_items > 0 && tot_items < max_ii(256, chunk_size * 2)) {
chunk_size = tot_items;
}
}
BLI_assert(chunk_size > 0);
switch (settings->scheduling_mode) {
case TASK_SCHEDULING_STATIC:
state->chunk_size = max_ii(chunk_size, tot_items / (num_tasks));
break;
case TASK_SCHEDULING_DYNAMIC:
state->chunk_size = chunk_size;
break;
}
}
BLI_INLINE bool parallel_range_next_iter_get(ParallelRangeState *__restrict state,
int *__restrict iter,
int *__restrict count)
{
int previter = atomic_fetch_and_add_int32(&state->iter, state->chunk_size);
*iter = previter;
*count = max_ii(0, min_ii(state->chunk_size, state->stop - previter));
return (previter < state->stop);
}
static void parallel_range_func(TaskPool *__restrict pool, void *userdata_chunk, int thread_id)
{
ParallelRangeState *__restrict state = BLI_task_pool_userdata(pool);
TaskParallelTLS tls = {
.thread_id = thread_id,
.userdata_chunk = userdata_chunk,
};
int iter, count;
while (parallel_range_next_iter_get(state, &iter, &count)) {
for (int i = 0; i < count; i++) {
state->func(state->userdata, iter + i, &tls);
}
}
}
static void parallel_range_single_thread(const int start,
int const stop,
void *userdata,
TaskParallelRangeFunc func,
const TaskParallelSettings *settings)
{
void *userdata_chunk = settings->userdata_chunk;
const size_t userdata_chunk_size = settings->userdata_chunk_size;
void *userdata_chunk_local = NULL;
const bool use_userdata_chunk = (userdata_chunk_size != 0) && (userdata_chunk != NULL);
if (use_userdata_chunk) {
userdata_chunk_local = MALLOCA(userdata_chunk_size);
memcpy(userdata_chunk_local, userdata_chunk, userdata_chunk_size);
}
TaskParallelTLS tls = {
.thread_id = 0,
.userdata_chunk = userdata_chunk_local,
};
for (int i = start; i < stop; i++) {
func(userdata, i, &tls);
}
if (settings->func_finalize != NULL) {
settings->func_finalize(userdata, userdata_chunk_local);
}
MALLOCA_FREE(userdata_chunk_local, userdata_chunk_size);
}
/**
* This function allows to parallelized for loops in a similar way to OpenMP's
* 'parallel for' statement.
*
* See public API doc of ParallelRangeSettings for description of all settings.
*/
void BLI_task_parallel_range(const int start,
const int stop,
void *userdata,
TaskParallelRangeFunc func,
const TaskParallelSettings *settings)
{
TaskScheduler *task_scheduler;
TaskPool *task_pool;
ParallelRangeState state;
int i, num_threads, num_tasks;
void *userdata_chunk = settings->userdata_chunk;
const size_t userdata_chunk_size = settings->userdata_chunk_size;
void *userdata_chunk_local = NULL;
void *userdata_chunk_array = NULL;
const bool use_userdata_chunk = (userdata_chunk_size != 0) && (userdata_chunk != NULL);
if (start == stop) {
return;
}
BLI_assert(start < stop);
if (userdata_chunk_size != 0) {
BLI_assert(userdata_chunk != NULL);
}
/* If it's not enough data to be crunched, don't bother with tasks at all,
* do everything from the main thread.
*/
if (!settings->use_threading) {
parallel_range_single_thread(start, stop, userdata, func, settings);
return;
}
task_scheduler = BLI_task_scheduler_get();
num_threads = BLI_task_scheduler_num_threads(task_scheduler);
/* The idea here is to prevent creating task for each of the loop iterations
* and instead have tasks which are evenly distributed across CPU cores and
* pull next iter to be crunched using the queue.
*/
num_tasks = num_threads + 2;
state.start = start;
state.stop = stop;
state.userdata = userdata;
state.func = func;
state.iter = start;
task_parallel_range_calc_chunk_size(settings, num_tasks, &state);
num_tasks = min_ii(num_tasks, max_ii(1, (stop - start) / state.chunk_size));
if (num_tasks == 1) {
parallel_range_single_thread(start, stop, userdata, func, settings);
return;
}
task_pool = BLI_task_pool_create_suspended(task_scheduler, &state);
/* NOTE: This way we are adding a memory barrier and ensure all worker
* threads can read and modify the value, without any locks. */
atomic_fetch_and_add_int32(&state.iter, 0);
if (use_userdata_chunk) {
userdata_chunk_array = MALLOCA(userdata_chunk_size * num_tasks);
}
for (i = 0; i < num_tasks; i++) {
if (use_userdata_chunk) {
userdata_chunk_local = (char *)userdata_chunk_array + (userdata_chunk_size * i);
memcpy(userdata_chunk_local, userdata_chunk, userdata_chunk_size);
}
/* Use this pool's pre-allocated tasks. */
BLI_task_pool_push_from_thread(task_pool,
parallel_range_func,
userdata_chunk_local,
false,
TASK_PRIORITY_HIGH,
task_pool->thread_id);
}
BLI_task_pool_work_and_wait(task_pool);
BLI_task_pool_free(task_pool);
if (use_userdata_chunk) {
if (settings->func_finalize != NULL) {
for (i = 0; i < num_tasks; i++) {
userdata_chunk_local = (char *)userdata_chunk_array + (userdata_chunk_size * i);
settings->func_finalize(userdata, userdata_chunk_local);
}
}
MALLOCA_FREE(userdata_chunk_array, userdata_chunk_size * num_tasks);
}
}
#undef MALLOCA
#undef MALLOCA_FREE
typedef struct ParallelListbaseState {
void *userdata;
TaskParallelListbaseFunc func;
int chunk_size;
int index;
Link *link;
SpinLock lock;
} ParallelListState;
BLI_INLINE Link *parallel_listbase_next_iter_get(ParallelListState *__restrict state,
int *__restrict index,
int *__restrict count)
{
int task_count = 0;
BLI_spin_lock(&state->lock);
Link *result = state->link;
if (LIKELY(result != NULL)) {
*index = state->index;
while (state->link != NULL && task_count < state->chunk_size) {
task_count++;
state->link = state->link->next;
}
state->index += task_count;
}
BLI_spin_unlock(&state->lock);
*count = task_count;
return result;
}
static void parallel_listbase_func(TaskPool *__restrict pool,
void *UNUSED(taskdata),
int UNUSED(threadid))
{
ParallelListState *__restrict state = BLI_task_pool_userdata(pool);
Link *link;
int index, count;
while ((link = parallel_listbase_next_iter_get(state, &index, &count)) != NULL) {
for (int i = 0; i < count; i++) {
state->func(state->userdata, link, index + i);
link = link->next;
}
}
}
static void task_parallel_listbase_no_threads(struct ListBase *listbase,
void *userdata,
TaskParallelListbaseFunc func)
{
int i = 0;
for (Link *link = listbase->first; link != NULL; link = link->next, i++) {
func(userdata, link, i);
}
}
/* NOTE: The idea here is to compensate for rather measurable threading
* overhead caused by fetching tasks. With too many CPU threads we are starting
* to spend too much time in those overheads. */
BLI_INLINE int task_parallel_listbasecalc_chunk_size(const int num_threads)
{
if (num_threads > 32) {
return 128;
}
else if (num_threads > 16) {
return 64;
}
return 32;
}
/**
* This function allows to parallelize for loops over ListBase items.
*
* \param listbase: The double linked list to loop over.
* \param userdata: Common userdata passed to all instances of \a func.
* \param func: Callback function.
* \param use_threading: If \a true, actually split-execute loop in threads,
* else just do a sequential forloop
* (allows caller to use any kind of test to switch on parallelization or not).
*
* \note There is no static scheduling here,
* since it would need another full loop over items to count them.
*/
void BLI_task_parallel_listbase(struct ListBase *listbase,
void *userdata,
TaskParallelListbaseFunc func,
const bool use_threading)
{
if (BLI_listbase_is_empty(listbase)) {
return;
}
if (!use_threading) {
task_parallel_listbase_no_threads(listbase, userdata, func);
return;
}
TaskScheduler *task_scheduler = BLI_task_scheduler_get();
const int num_threads = BLI_task_scheduler_num_threads(task_scheduler);
/* TODO(sergey): Consider making chunk size configurable. */
const int chunk_size = task_parallel_listbasecalc_chunk_size(num_threads);
const int num_tasks = min_ii(num_threads, BLI_listbase_count(listbase) / chunk_size);
if (num_tasks <= 1) {
task_parallel_listbase_no_threads(listbase, userdata, func);
return;
}
ParallelListState state;
TaskPool *task_pool = BLI_task_pool_create_suspended(task_scheduler, &state);
state.index = 0;
state.link = listbase->first;
state.userdata = userdata;
state.func = func;
state.chunk_size = chunk_size;
BLI_spin_init(&state.lock);
BLI_assert(num_tasks > 0);
for (int i = 0; i < num_tasks; i++) {
/* Use this pool's pre-allocated tasks. */
BLI_task_pool_push_from_thread(
task_pool, parallel_listbase_func, NULL, false, TASK_PRIORITY_HIGH, task_pool->thread_id);
}
BLI_task_pool_work_and_wait(task_pool);
BLI_task_pool_free(task_pool);
BLI_spin_end(&state.lock);
}
typedef struct ParallelMempoolState {
void *userdata;
TaskParallelMempoolFunc func;
} ParallelMempoolState;
static void parallel_mempool_func(TaskPool *__restrict pool, void *taskdata, int UNUSED(threadid))
{
ParallelMempoolState *__restrict state = BLI_task_pool_userdata(pool);
BLI_mempool_iter *iter = taskdata;
MempoolIterData *item;
while ((item = BLI_mempool_iterstep(iter)) != NULL) {
state->func(state->userdata, item);
}
}
/**
* This function allows to parallelize for loops over Mempool items.
*
* \param mempool: The iterable BLI_mempool to loop over.
* \param userdata: Common userdata passed to all instances of \a func.
* \param func: Callback function.
* \param use_threading: If \a true, actually split-execute loop in threads,
* else just do a sequential for loop
* (allows caller to use any kind of test to switch on parallelization or not).
*
* \note There is no static scheduling here.
*/
void BLI_task_parallel_mempool(BLI_mempool *mempool,
void *userdata,
TaskParallelMempoolFunc func,
const bool use_threading)
{
TaskScheduler *task_scheduler;
TaskPool *task_pool;
ParallelMempoolState state;
int i, num_threads, num_tasks;
if (BLI_mempool_len(mempool) == 0) {
return;
}
if (!use_threading) {
BLI_mempool_iter iter;
BLI_mempool_iternew(mempool, &iter);
for (void *item = BLI_mempool_iterstep(&iter); item != NULL;
item = BLI_mempool_iterstep(&iter)) {
func(userdata, item);
}
return;
}
task_scheduler = BLI_task_scheduler_get();
task_pool = BLI_task_pool_create_suspended(task_scheduler, &state);
num_threads = BLI_task_scheduler_num_threads(task_scheduler);
/* The idea here is to prevent creating task for each of the loop iterations
* and instead have tasks which are evenly distributed across CPU cores and
* pull next item to be crunched using the threaded-aware BLI_mempool_iter.
*/
num_tasks = num_threads + 2;
state.userdata = userdata;
state.func = func;
BLI_mempool_iter *mempool_iterators = BLI_mempool_iter_threadsafe_create(mempool,
(size_t)num_tasks);
for (i = 0; i < num_tasks; i++) {
/* Use this pool's pre-allocated tasks. */
BLI_task_pool_push_from_thread(task_pool,
parallel_mempool_func,
&mempool_iterators[i],
false,
TASK_PRIORITY_HIGH,
task_pool->thread_id);
}
BLI_task_pool_work_and_wait(task_pool);
BLI_task_pool_free(task_pool);
BLI_mempool_iter_threadsafe_free(mempool_iterators);
}
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