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Diffstat (limited to 'module/zfs/bqueue.c')
| -rw-r--r-- | module/zfs/bqueue.c | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/module/zfs/bqueue.c b/module/zfs/bqueue.c new file mode 100644 index 000000000000..22539efc4e23 --- /dev/null +++ b/module/zfs/bqueue.c @@ -0,0 +1,155 @@ +/* + * CDDL HEADER START + * + * This file and its contents are supplied under the terms of the + * Common Development and Distribution License ("CDDL"), version 1.0. + * You may only use this file in accordance with the terms of version + * 1.0 of the CDDL. + * + * A full copy of the text of the CDDL should have accompanied this + * source. A copy of the CDDL is also available via the Internet at + * http://www.illumos.org/license/CDDL. + * + * CDDL HEADER END + */ +/* + * Copyright (c) 2014, 2018 by Delphix. All rights reserved. + */ + +#include <sys/bqueue.h> +#include <sys/zfs_context.h> + +static inline bqueue_node_t * +obj2node(bqueue_t *q, void *data) +{ + return ((bqueue_node_t *)((char *)data + q->bq_node_offset)); +} + +/* + * Initialize a blocking queue The maximum capacity of the queue is set to + * size. Types that are stored in a bqueue must contain a bqueue_node_t, + * and node_offset must be its offset from the start of the struct. + * fill_fraction is a performance tuning value; when the queue is full, any + * threads attempting to enqueue records will block. They will block until + * they're signaled, which will occur when the queue is at least 1/fill_fraction + * empty. Similar behavior occurs on dequeue; if the queue is empty, threads + * block. They will be signalled when the queue has 1/fill_fraction full, or + * when bqueue_flush is called. As a result, you must call bqueue_flush when + * you enqueue your final record on a thread, in case the dequeueing threads are + * currently blocked and that enqueue does not cause them to be awoken. + * Alternatively, this behavior can be disabled (causing signaling to happen + * immediately) by setting fill_fraction to any value larger than size. + * Return 0 on success, or -1 on failure. + */ +int +bqueue_init(bqueue_t *q, uint64_t fill_fraction, uint64_t size, + size_t node_offset) +{ + if (fill_fraction == 0) { + return (-1); + } + list_create(&q->bq_list, node_offset + sizeof (bqueue_node_t), + node_offset + offsetof(bqueue_node_t, bqn_node)); + cv_init(&q->bq_add_cv, NULL, CV_DEFAULT, NULL); + cv_init(&q->bq_pop_cv, NULL, CV_DEFAULT, NULL); + mutex_init(&q->bq_lock, NULL, MUTEX_DEFAULT, NULL); + q->bq_node_offset = node_offset; + q->bq_size = 0; + q->bq_maxsize = size; + q->bq_fill_fraction = fill_fraction; + return (0); +} + +/* + * Destroy a blocking queue. This function asserts that there are no + * elements in the queue, and no one is blocked on the condition + * variables. + */ +void +bqueue_destroy(bqueue_t *q) +{ + mutex_enter(&q->bq_lock); + ASSERT0(q->bq_size); + cv_destroy(&q->bq_add_cv); + cv_destroy(&q->bq_pop_cv); + list_destroy(&q->bq_list); + mutex_exit(&q->bq_lock); + mutex_destroy(&q->bq_lock); +} + +static void +bqueue_enqueue_impl(bqueue_t *q, void *data, uint64_t item_size, + boolean_t flush) +{ + ASSERT3U(item_size, >, 0); + ASSERT3U(item_size, <=, q->bq_maxsize); + mutex_enter(&q->bq_lock); + obj2node(q, data)->bqn_size = item_size; + while (q->bq_size + item_size > q->bq_maxsize) { + cv_wait_sig(&q->bq_add_cv, &q->bq_lock); + } + q->bq_size += item_size; + list_insert_tail(&q->bq_list, data); + if (q->bq_size >= q->bq_maxsize / q->bq_fill_fraction) + cv_signal(&q->bq_pop_cv); + if (flush) + cv_broadcast(&q->bq_pop_cv); + mutex_exit(&q->bq_lock); +} + +/* + * Add data to q, consuming size units of capacity. If there is insufficient + * capacity to consume size units, block until capacity exists. Asserts size is + * > 0. + */ +void +bqueue_enqueue(bqueue_t *q, void *data, uint64_t item_size) +{ + bqueue_enqueue_impl(q, data, item_size, B_FALSE); +} + +/* + * Enqueue an entry, and then flush the queue. This forces the popping threads + * to wake up, even if we're below the fill fraction. We have this in a single + * function, rather than having a separate call, because it prevents race + * conditions between the enqueuing thread and the dequeueing thread, where the + * enqueueing thread will wake up the dequeueing thread, that thread will + * destroy the condvar before the enqueuing thread is done. + */ +void +bqueue_enqueue_flush(bqueue_t *q, void *data, uint64_t item_size) +{ + bqueue_enqueue_impl(q, data, item_size, B_TRUE); +} + +/* + * Take the first element off of q. If there are no elements on the queue, wait + * until one is put there. Return the removed element. + */ +void * +bqueue_dequeue(bqueue_t *q) +{ + void *ret = NULL; + uint64_t item_size; + mutex_enter(&q->bq_lock); + while (q->bq_size == 0) { + cv_wait_sig(&q->bq_pop_cv, &q->bq_lock); + } + ret = list_remove_head(&q->bq_list); + ASSERT3P(ret, !=, NULL); + item_size = obj2node(q, ret)->bqn_size; + q->bq_size -= item_size; + if (q->bq_size <= q->bq_maxsize - (q->bq_maxsize / q->bq_fill_fraction)) + cv_signal(&q->bq_add_cv); + mutex_exit(&q->bq_lock); + return (ret); +} + +/* + * Returns true if the space used is 0. + */ +boolean_t +bqueue_empty(bqueue_t *q) +{ + return (q->bq_size == 0); +} |