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Before Direct I/O was implemented, I've implemented lighter version I called Uncached I/O. It uses normal DMU/ARC data path with some optimizations, but evicts data from caches as soon as possible and reasonable. Originally I wired it only to a primarycache property, but now completing the integration all the way up to the VFS. While Direct I/O has the lowest possible memory bandwidth usage, it also has a significant number of limitations. It require I/Os to be page aligned, does not allow speculative prefetch, etc. The Uncached I/O does not have those limitations, but instead require additional memory copy, though still one less than regular cached I/O. As such it should fill the gap in between. Considering this I've disabled annoying EINVAL errors on misaligned requests, adding a tunable for those who wants to test their applications. To pass the information between the layers I had to change a number of APIs. But as side effect upper layers can now control not only the caching, but also speculative prefetch. I haven't wired it to VFS yet, since it require looking on some OS specifics. But while there I've implemented speculative prefetch of indirect blocks for Direct I/O, controllable via all the same mechanisms. Signed-off-by: Alexander Motin <mav@FreeBSD.org> Sponsored by: iXsystems, Inc. Fixes #17027 Reviewed-by: Rob Norris <robn@despairlabs.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
95 lines
2.9 KiB
C
95 lines
2.9 KiB
C
// SPDX-License-Identifier: CDDL-1.0
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/*
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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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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, 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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