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For quite some time I was thinking about possibility to prefetch
ZFS indirection tables while doing sequential reads or writes.
Recent changes in predictive prefetcher made that much easier to
do. My tests on zvol with 16KB block size on 5x striped and 2x
mirrored pool of 10 disks show almost double throughput on sequential
read, and almost tripple on sequential rewrite. While for read alike
effect can be received from increasing maximal prefetch distance
(though at higher memory cost), for rewrite there is no other
solution so far.
Authored by: Alexander Motin <mav@freebsd.org>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Ported-by: kernelOfTruth kerneloftruth@gmail.com
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
OpenZFS-issue: https://www.illumos.org/issues/6322
OpenZFS-commit: https://github.com/illumos/illumos-gate/commit/cb92f413
Closes #5040
Porting notes:
- Change from upstream in module/zfs/dbuf.c in 'int dbuf_read' due
to commit 5f6d0b6 'Handle block pointers with a corrupt logical size'
- Difference from upstream in module/zfs/dmu_zfetch.c,
uint32_t zfetch_max_idistance -> unsigned int zfetch_max_idistance
- Variables have been initialized at the beginning of the function
(void dmu_zfetch) to resemble the order of occurrence and account
for C99, C11 mode errors.
77 lines
2.0 KiB
C
77 lines
2.0 KiB
C
/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License (the "License").
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* You may not use this file except in compliance with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or http://www.opensolaris.org/os/licensing.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright 2009 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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/*
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* Copyright (c) 2014 by Delphix. All rights reserved.
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*/
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#ifndef _DMU_ZFETCH_H
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#define _DMU_ZFETCH_H
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#include <sys/zfs_context.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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extern unsigned long zfetch_array_rd_sz;
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struct dnode; /* so we can reference dnode */
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typedef struct zstream {
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uint64_t zs_blkid; /* expect next access at this blkid */
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uint64_t zs_pf_blkid; /* next block to prefetch */
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/*
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* We will next prefetch the L1 indirect block of this level-0
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* block id.
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*/
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uint64_t zs_ipf_blkid;
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kmutex_t zs_lock; /* protects stream */
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hrtime_t zs_atime; /* time last prefetch issued */
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list_node_t zs_node; /* link for zf_stream */
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} zstream_t;
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typedef struct zfetch {
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krwlock_t zf_rwlock; /* protects zfetch structure */
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list_t zf_stream; /* list of zstream_t's */
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struct dnode *zf_dnode; /* dnode that owns this zfetch */
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} zfetch_t;
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void zfetch_init(void);
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void zfetch_fini(void);
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void dmu_zfetch_init(zfetch_t *, struct dnode *);
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void dmu_zfetch_fini(zfetch_t *);
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void dmu_zfetch(zfetch_t *, uint64_t, uint64_t, boolean_t);
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#ifdef __cplusplus
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}
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#endif
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#endif /* _DMU_ZFETCH_H */
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