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5e5fd0a178
Before this change speculative prefetcher was able to detect a stream only if all of its accesses are perfectly sequential. It was easy to implement and is perfectly fine for single-threaded applications. Unfortunately multi-threaded network servers, such as iSCSI, SMB or NFS usually have plenty of threads and may often reorder requests, preventing successful speculation and prefetch. This change allows speculative prefetcher to detect streams even if requests are reordered by introducing a list of 9 non-contiguous ranges up to 16MB ahead of current stream position and filling the gaps as more requests arrive. It also allows stream to proceed even with holes up to a certain configurable threshold (25%). Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Alexander Motin <mav@FreeBSD.org> Sponsored by: iXsystems, Inc. Closes #16022
93 lines
2.9 KiB
C
93 lines
2.9 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 https://opensource.org/licenses/CDDL-1.0.
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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, 2017 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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struct dnode; /* so we can reference dnode */
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typedef struct zfetch {
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kmutex_t zf_lock; /* 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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int zf_numstreams; /* number of zstream_t's */
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} zfetch_t;
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typedef struct zsrange {
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uint16_t start;
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uint16_t end;
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} zsrange_t;
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#define ZFETCH_RANGES 9 /* Fits zstream_t into 128 bytes */
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typedef struct zstream {
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list_node_t zs_node; /* link for zf_stream */
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uint64_t zs_blkid; /* expect next access at this blkid */
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uint_t zs_atime; /* time last prefetch issued */
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zsrange_t zs_ranges[ZFETCH_RANGES]; /* ranges from future */
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unsigned int zs_pf_dist; /* data prefetch distance in bytes */
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unsigned int zs_ipf_dist; /* L1 prefetch distance in bytes */
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uint64_t zs_pf_start; /* first data block to prefetch */
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uint64_t zs_pf_end; /* data block to prefetch up to */
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uint64_t zs_ipf_start; /* first data block to prefetch L1 */
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uint64_t zs_ipf_end; /* data block to prefetch L1 up to */
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boolean_t zs_missed; /* stream saw cache misses */
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boolean_t zs_more; /* need more distant prefetch */
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zfs_refcount_t zs_callers; /* number of pending callers */
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/*
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* Number of stream references: dnode, callers and pending blocks.
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* The stream memory is freed when the number returns to zero.
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*/
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zfs_refcount_t zs_refs;
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} zstream_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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zstream_t *dmu_zfetch_prepare(zfetch_t *, uint64_t, uint64_t, boolean_t,
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boolean_t);
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void dmu_zfetch_run(zfetch_t *, zstream_t *, boolean_t, boolean_t);
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void dmu_zfetch(zfetch_t *, uint64_t, uint64_t, boolean_t, boolean_t,
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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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