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lib: Implement thread pool and use it for BVH building
I was intending on simplifying the main renderer thread management with this as well, but on second thought, this isn't really a good fit for that. The current approach gives us load balancing for free, since the fixed render threads just pick up new tiles to render as soon as they finish the previous one. Using this thread pool for rendering will require a bit more planning.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,158 @@ | ||
| // | ||
| // thread_pool.c | ||
| // c-ray | ||
| // | ||
| // Created by Valtteri on 04.1.2024. | ||
| // Copyright © 2024 Valtteri Koskivuori. All rights reserved. | ||
| // | ||
|
|
||
| #include "thread_pool.h" | ||
| #include "mutex.h" | ||
| #include "thread.h" | ||
| #include "../logging.h" | ||
|
|
||
| struct cr_task { | ||
| void (*fn)(void *arg); | ||
| void *arg; | ||
| struct cr_task *next; | ||
| }; | ||
|
|
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| struct cr_thread_pool { | ||
| struct cr_task *first; | ||
| struct cr_task *last; | ||
| struct cr_mutex *mutex; | ||
| struct cr_cond work_available; | ||
| struct cr_cond work_ongoing; | ||
| size_t active_workers; | ||
| struct cr_thread *threads; | ||
| size_t thread_count; | ||
| bool stop_flag; | ||
| }; | ||
|
|
||
| static struct cr_task *task_create(void (*fn)(void *arg), void *arg) { | ||
| if (!fn) return NULL; | ||
| struct cr_task *task = malloc(sizeof(*task)); | ||
| *task = (struct cr_task){ | ||
| .fn = fn, | ||
| .arg = arg, | ||
| .next = NULL | ||
| }; | ||
| return task; | ||
| } | ||
|
|
||
| static struct cr_task *thread_pool_get_task(struct cr_thread_pool *pool) { | ||
| if (!pool) return NULL; | ||
| struct cr_task *task = pool->first; | ||
| if (!task) return NULL; | ||
| if (!task->next) { | ||
| pool->first = NULL; | ||
| pool->last = NULL; | ||
| } else { | ||
| pool->first = task->next; | ||
| } | ||
| return task; | ||
| } | ||
|
|
||
| static void *cr_worker(void *arg) { | ||
| struct cr_thread_pool *pool = thread_user_data(arg); | ||
| while (true) { | ||
| mutex_lock(pool->mutex); | ||
| while (!pool->first && !pool->stop_flag) | ||
| thread_cond_wait(&pool->work_available, pool->mutex); | ||
| if (pool->stop_flag) break; | ||
| struct cr_task *task = thread_pool_get_task(pool); | ||
| pool->active_workers++; | ||
| mutex_release(pool->mutex); | ||
| if (task) { | ||
| task->fn(task->arg); | ||
| free(task); | ||
| } | ||
| mutex_lock(pool->mutex); | ||
| pool->active_workers--; | ||
| if (!pool->stop_flag && pool->active_workers == 0 && !pool->first) | ||
| thread_cond_signal(&pool->work_ongoing); | ||
| mutex_release(pool->mutex); | ||
| } | ||
| pool->thread_count--; | ||
| thread_cond_signal(&pool->work_ongoing); | ||
| mutex_release(pool->mutex); | ||
| return NULL; | ||
| } | ||
|
|
||
| struct cr_thread_pool *thread_pool_create(size_t threads) { | ||
| if (!threads) threads = 2; | ||
| struct cr_thread_pool *pool = calloc(1, sizeof(*pool)); | ||
| logr(debug, "Spawning thread pool (%lut, %p)\n", threads, (void *)pool); | ||
| pool->thread_count = threads; | ||
| pool->threads = calloc(pool->thread_count, sizeof(*pool->threads)); | ||
|
|
||
| pool->mutex = mutex_create(); | ||
| thread_cond_init(&pool->work_available); | ||
| thread_cond_init(&pool->work_ongoing); | ||
|
|
||
| for (size_t i = 0; i < pool->thread_count; ++i) { | ||
| pool->threads[i] = (struct cr_thread){ | ||
| .thread_fn = cr_worker, | ||
| .user_data = pool | ||
| }; | ||
| thread_create_detach(&pool->threads[i]); | ||
| } | ||
| return pool; | ||
| } | ||
|
|
||
| void thread_pool_destroy(struct cr_thread_pool *pool) { | ||
| if (!pool) return; | ||
| logr(debug, "Closing thread pool (%lut, %p)\n", pool->thread_count, (void *)pool); | ||
| mutex_lock(pool->mutex); | ||
| // Clear work queue | ||
| struct cr_task *head = pool->first; | ||
| struct cr_task *next = NULL; | ||
| while (head) { | ||
| next = head->next; | ||
| free(head); | ||
| head = next; | ||
| } | ||
| // Tell the workers to stop | ||
| pool->stop_flag = true; | ||
| thread_cond_broadcast(&pool->work_available); | ||
| mutex_release(pool->mutex); | ||
|
|
||
| // Wait for them to actually stop | ||
| thread_pool_wait(pool); | ||
|
|
||
| mutex_destroy(pool->mutex); | ||
| thread_cond_destroy(&pool->work_available); | ||
| thread_cond_destroy(&pool->work_ongoing); | ||
| free(pool->threads); | ||
| free(pool); | ||
| } | ||
|
|
||
| bool thread_pool_enqueue(struct cr_thread_pool *pool, void (*fn)(void *arg), void *arg) { | ||
| if (!pool) return false; | ||
| struct cr_task *task = task_create(fn, arg); | ||
| if (!task) return false; | ||
| mutex_lock(pool->mutex); | ||
| if (!pool->first) { | ||
| pool->first = task; | ||
| pool->last = pool->first; | ||
| } else { | ||
| pool->last->next = task; | ||
| pool->last = task; | ||
| } | ||
| thread_cond_broadcast(&pool->work_available); | ||
| mutex_release(pool->mutex); | ||
| return true; | ||
| } | ||
|
|
||
| void thread_pool_wait(struct cr_thread_pool *pool) { | ||
| if (!pool) return; | ||
| mutex_lock(pool->mutex); | ||
| while (true) { | ||
| if ((!pool->stop_flag && pool->active_workers != 0) || (pool->stop_flag && pool->thread_count != 0)) { | ||
| thread_cond_wait(&pool->work_ongoing, pool->mutex); | ||
| } else { | ||
| break; | ||
| } | ||
| } | ||
| mutex_release(pool->mutex); | ||
| } |
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