fc45975ec8
The Blocking Queue (bqueue) code is used by zfs send/receive to send messages between the various threads. It uses a shared linked list, which is locked whenever we enqueue or dequeue. For workloads which process many blocks per second, the locking on the shared list can be quite expensive. This commit changes the bqueue logic to have 3 linked lists: 1. An enquing list, which is used only by the (single) enquing thread, and thus needs no locks. 2. A shared list, with an associated lock. 3. A dequing list, which is used only by the (single) dequing thread, and thus needs no locks. The entire enquing list can be moved to the shared list in constant time, and the entire shared list can be moved to the dequing list in constant time. These operations only happen when the `fill_fraction` is reached, or on an explicit flush request. Therefore, the lock only needs to be acquired infrequently. The API already allows for dequing to block until an explicit flush, so callers don't need to be changed. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #14121
60 lines
1.3 KiB
C
60 lines
1.3 KiB
C
/*
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* CDDL HEADER START
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*
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* This file and its contents are supplied under the terms of the
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* Common Development and Distribution License ("CDDL"), version 1.0.
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* You may only use this file in accordance with the terms of version
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* 1.0 of the CDDL.
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*
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* A full copy of the text of the CDDL should have accompanied this
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* source. A copy of the CDDL is also available via the Internet at
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* http://www.illumos.org/license/CDDL.
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright (c) 2014, 2018 by Delphix. All rights reserved.
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*/
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#ifndef _BQUEUE_H
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#define _BQUEUE_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include <sys/zfs_context.h>
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typedef struct bqueue {
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list_t bq_list;
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size_t bq_size;
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list_t bq_dequeuing_list;
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size_t bq_dequeuing_size;
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list_t bq_enqueuing_list;
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size_t bq_enqueuing_size;
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kmutex_t bq_lock;
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kcondvar_t bq_add_cv;
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kcondvar_t bq_pop_cv;
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size_t bq_maxsize;
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uint_t bq_fill_fraction;
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size_t bq_node_offset;
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} bqueue_t;
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typedef struct bqueue_node {
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list_node_t bqn_node;
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size_t bqn_size;
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} bqueue_node_t;
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int bqueue_init(bqueue_t *, uint_t, size_t, size_t);
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void bqueue_destroy(bqueue_t *);
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void bqueue_enqueue(bqueue_t *, void *, size_t);
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void bqueue_enqueue_flush(bqueue_t *, void *, size_t);
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void *bqueue_dequeue(bqueue_t *);
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#ifdef __cplusplus
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}
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#endif
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#endif /* _BQUEUE_H */
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