From 73e071eabefd4554271759471c4ba04313e76f6b Mon Sep 17 00:00:00 2001 From: Gregory Burd Date: Fri, 26 Jul 2013 14:33:40 -0400 Subject: [PATCH] Update to latest async work. --- c_src/async_nif.h | 65 ++++++++++++++++++++++++++++------------------- 1 file changed, 39 insertions(+), 26 deletions(-) diff --git a/c_src/async_nif.h b/c_src/async_nif.h index 8f13913..5d283da 100644 --- a/c_src/async_nif.h +++ b/c_src/async_nif.h @@ -53,6 +53,7 @@ struct async_nif_work_queue { unsigned int depth; ErlNifMutex *reqs_mutex; ErlNifCond *reqs_cnd; + struct async_nif_work_queue *next; STAILQ_HEAD(reqs, async_nif_req_entry) reqs; }; @@ -148,14 +149,14 @@ struct async_nif_state { #define ASYNC_NIF_LOAD(name, priv) do { \ if (!name##_async_nif_coord) \ - name##_async_nif_coord = enif_mutex_create(NULL); \ + name##_async_nif_coord = enif_mutex_create("nif_coord load"); \ enif_mutex_lock(name##_async_nif_coord); \ priv = async_nif_load(); \ enif_mutex_unlock(name##_async_nif_coord); \ } while(0); #define ASYNC_NIF_UNLOAD(name, env, priv) do { \ if (!name##_async_nif_coord) \ - name##_async_nif_coord = enif_mutex_create(NULL); \ + name##_async_nif_coord = enif_mutex_create("nif_coord unload"); \ enif_mutex_lock(name##_async_nif_coord); \ async_nif_unload(env, priv); \ enif_mutex_unlock(name##_async_nif_coord); \ @@ -164,7 +165,7 @@ struct async_nif_state { } while(0); #define ASYNC_NIF_UPGRADE(name, env) do { \ if (!name##_async_nif_coord) \ - name##_async_nif_coord = enif_mutex_create(NULL); \ + name##_async_nif_coord = enif_mutex_create("nif_coord upgrade"); \ enif_mutex_lock(name##_async_nif_coord); \ async_nif_upgrade(env); \ enif_mutex_unlock(name##_async_nif_coord); \ @@ -197,7 +198,7 @@ async_nif_reuse_req(struct async_nif_state *async_nif) env = enif_alloc_env(); if (env) { req->env = env; - async_nif->num_reqs++; + __sync_fetch_and_add(&async_nif->num_reqs, 1); } else { enif_free(req); req = NULL; @@ -287,9 +288,9 @@ static ERL_NIF_TERM async_nif_enqueue_req(struct async_nif_state* async_nif, struct async_nif_req_entry *req, int hint) { /* Identify the most appropriate worker for this request. */ - unsigned int i, qid = 0; + unsigned int i, last_qid, qid = 0; struct async_nif_work_queue *q = NULL; - double avg_depth = 0.0; + double avg_depth; /* Either we're choosing a queue based on some affinity/hinted value or we need to select the next queue in the rotation and atomically update that @@ -297,9 +298,10 @@ async_nif_enqueue_req(struct async_nif_state* async_nif, struct async_nif_req_en if (hint >= 0) { qid = (unsigned int)hint; } else { - qid = async_nif->next_q; - qid = (qid + 1) % async_nif->num_queues; - async_nif->next_q = qid; + do { + last_qid = __sync_fetch_and_add(&async_nif->next_q, 0); + qid = (last_qid + 1) % async_nif->num_queues; + } while (!__sync_bool_compare_and_swap(&async_nif->next_q, last_qid, qid)); } /* Now we inspect and interate across the set of queues trying to select one @@ -314,8 +316,7 @@ async_nif_enqueue_req(struct async_nif_state* async_nif, struct async_nif_req_en avg_depth += async_nif->queues[j].depth; } } - if (avg_depth != 0) - avg_depth /= n; + if (avg_depth) avg_depth /= n; /* Lock this queue under consideration, then check for shutdown. While we hold this lock either a) we're shutting down so exit now or b) this @@ -337,20 +338,23 @@ async_nif_enqueue_req(struct async_nif_state* async_nif, struct async_nif_req_en } /* If the for loop finished then we didn't find a suitable queue for this - request, meaning we're backed up so trigger eagain. */ - if (i == async_nif->num_queues) { - enif_mutex_unlock(q->reqs_mutex); - return 0; - } + request, meaning we're backed up so trigger eagain. Note that if we left + the loop in this way we hold no lock. */ + if (i == async_nif->num_queues) return 0; /* Add the request to the queue. */ STAILQ_INSERT_TAIL(&q->reqs, req, entries); - q->depth++; + __sync_fetch_and_add(&q->depth, 1); /* We've selected a queue for this new request now check to make sure there are enough workers actively processing requests on this queue. */ - if (q->depth > q->num_workers) - if (async_nif_start_worker(async_nif, q) == 0) q->num_workers++; + while (q->depth > q->num_workers) { + switch(async_nif_start_worker(async_nif, q)) { + case EINVAL: case ENOMEM: default: return 0; + case EAGAIN: continue; + case 0: __sync_fetch_and_add(&q->num_workers, 1); goto done; + } + }done:; /* Build the term before releasing the lock so as not to race on the use of the req pointer (which will soon become invalid in another thread @@ -375,6 +379,7 @@ async_nif_worker_fn(void *arg) struct async_nif_state *async_nif = we->async_nif; struct async_nif_work_queue *q = we->q; struct async_nif_req_entry *req = NULL; + unsigned int tries = async_nif->num_queues; for(;;) { /* Examine the request queue, are there things to be done? */ @@ -388,7 +393,14 @@ async_nif_worker_fn(void *arg) /* Queue is empty so we wait for more work to arrive. */ if (q->num_workers > ASYNC_NIF_MIN_WORKERS) { enif_mutex_unlock(q->reqs_mutex); - break; + if (tries == 0 && q == we->q) break; // we've tried all queues, thread exit + else { + tries--; + __sync_fetch_and_add(&q->num_workers, -1); + q = q->next; + __sync_fetch_and_add(&q->num_workers, 1); + continue; // try another queue + } } else { enif_cond_wait(q->reqs_cnd, q->reqs_mutex); goto check_again_for_work; @@ -398,7 +410,7 @@ async_nif_worker_fn(void *arg) reqs_mutex lock. Take the request off the queue. */ req = STAILQ_FIRST(&q->reqs); STAILQ_REMOVE(&q->reqs, req, async_nif_req_entry, entries); - q->depth--; + __sync_fetch_and_add(&q->depth, -1); /* Ensure that there is at least one other worker thread watching this queue. */ @@ -424,7 +436,7 @@ async_nif_worker_fn(void *arg) enif_mutex_lock(async_nif->we_mutex); SLIST_INSERT_HEAD(&async_nif->we_joining, we, entries); enif_mutex_unlock(async_nif->we_mutex); - q->num_workers--; + __sync_fetch_and_add(&q->num_workers, -1); enif_thread_exit(0); return 0; } @@ -556,15 +568,16 @@ async_nif_load() async_nif->next_q = 0; async_nif->shutdown = 0; STAILQ_INIT(&async_nif->recycled_reqs); - async_nif->recycled_req_mutex = enif_mutex_create(NULL); - async_nif->we_mutex = enif_mutex_create(NULL); + async_nif->recycled_req_mutex = enif_mutex_create("recycled_req"); + async_nif->we_mutex = enif_mutex_create("we"); SLIST_INIT(&async_nif->we_joining); for (i = 0; i < async_nif->num_queues; i++) { struct async_nif_work_queue *q = &async_nif->queues[i]; STAILQ_INIT(&q->reqs); - q->reqs_mutex = enif_mutex_create(NULL); - q->reqs_cnd = enif_cond_create(NULL); + q->reqs_mutex = enif_mutex_create("reqs"); + q->reqs_cnd = enif_cond_create("reqs"); + q->next = &async_nif->queues[(i + 1) % num_queues]; } return async_nif; }