2bb93f2d18
the order that they arrive, to holding (a) granted write lock requests, followed by (b) granted read lock requests, followed by (c) ungranted requests, in order of arrival. This changes the stopping condition for iterating through granted locks to see if a new request can be granted: When considering a read lock request, we can stop iterating as soon as we see a read lock request, since anything after that point is either a granted read lock request or a request which has not yet been granted. (For write lock requests, we must still compare against all granted lock requests.) For workloads with R parallel reads and W parallel writes, this improves the time spent from O((R+W)^2) to O(W*(R+W)); i.e., heavy parallel-read workloads become significantly more scalable. No statistically significant change in buildworld time has been measured, but synthetic tests of parallel 'dd > /dev/null' and 'openssl enc >/dev/null' with the input file cached yield dramatic (up to 10x) improvement with high (up to 128 processes) levels of parallelism. Reviewed by: kib
83 lines
3.0 KiB
C
83 lines
3.0 KiB
C
/*-
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* Copyright (c) 2009 Konstantin Belousov <kib@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice unmodified, this list of conditions, and the following
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* disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef _SYS_RANGELOCK_H
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#define _SYS_RANGELOCK_H
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#include <sys/queue.h>
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#define RL_LOCK_READ 0x0001
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#define RL_LOCK_WRITE 0x0002
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#define RL_LOCK_TYPE_MASK 0x0003
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#define RL_LOCK_GRANTED 0x0004
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struct rl_q_entry;
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/*
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* The structure representing the range lock. Caller may request
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* read or write access to the range of bytes. Access is granted if
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* all existing lock owners are compatible with the request. Two lock
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* owners are compatible if their ranges do not overlap, or both
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* owners are for read.
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*
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* Access to the structure itself is synchronized with the externally
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* supplied mutex.
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*
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* rl_waiters is the queue containing in order (a) granted write lock
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* requests, (b) granted read lock requests, and (c) in order of arrival,
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* lock requests which cannot be granted yet.
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*
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* rl_currdep is the first lock request that cannot be granted now due
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* to the preceding requests conflicting with it (i.e., it points to
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* position (c) in the list above).
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*/
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struct rangelock {
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TAILQ_HEAD(, rl_q_entry) rl_waiters;
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struct rl_q_entry *rl_currdep;
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};
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#ifdef _KERNEL
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struct mtx;
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void rangelock_init(struct rangelock *lock);
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void rangelock_destroy(struct rangelock *lock);
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void rangelock_unlock(struct rangelock *lock, void *cookie,
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struct mtx *ilk);
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void *rangelock_unlock_range(struct rangelock *lock, void *cookie,
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off_t start, off_t end, struct mtx *ilk);
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void *rangelock_rlock(struct rangelock *lock, off_t start, off_t end,
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struct mtx *ilk);
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void *rangelock_wlock(struct rangelock *lock, off_t start, off_t end,
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struct mtx *ilk);
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void rlqentry_free(struct rl_q_entry *rlqe);
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#endif /* _KERNEL */
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#endif /* _SYS_RANGELOCK_H */
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