/* * CDDL HEADER START * * The contents of this file are subject to the terms of the * Common Development and Distribution License (the "License"). * You may not use this file except in compliance with the License. * * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE * or http://www.opensolaris.org/os/licensing. * See the License for the specific language governing permissions * and limitations under the License. * * When distributing Covered Code, include this CDDL HEADER in each * file and include the License file at usr/src/OPENSOLARIS.LICENSE. * If applicable, add the following below this CDDL HEADER, with the * fields enclosed by brackets "[]" replaced with your own identifying * information: Portions Copyright [yyyy] [name of copyright owner] * * CDDL HEADER END */ /* * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. */ #include #include #include #include #include #include /* * I'm against tune-ables, but these should probably exist as tweakable globals * until we can get this working the way we want it to. */ int zfs_prefetch_disable = 0; /* max # of streams per zfetch */ uint32_t zfetch_max_streams = 8; /* min time before stream reclaim */ uint32_t zfetch_min_sec_reap = 2; /* max number of blocks to fetch at a time */ uint32_t zfetch_block_cap = 256; /* number of bytes in a array_read at which we stop prefetching (1Mb) */ uint64_t zfetch_array_rd_sz = 1024 * 1024; /* forward decls for static routines */ static int dmu_zfetch_colinear(zfetch_t *, zstream_t *); static void dmu_zfetch_dofetch(zfetch_t *, zstream_t *); static uint64_t dmu_zfetch_fetch(dnode_t *, uint64_t, uint64_t); static uint64_t dmu_zfetch_fetchsz(dnode_t *, uint64_t, uint64_t); static int dmu_zfetch_find(zfetch_t *, zstream_t *, int); static int dmu_zfetch_stream_insert(zfetch_t *, zstream_t *); static zstream_t *dmu_zfetch_stream_reclaim(zfetch_t *); static void dmu_zfetch_stream_remove(zfetch_t *, zstream_t *); static int dmu_zfetch_streams_equal(zstream_t *, zstream_t *); /* * Given a zfetch structure and a zstream structure, determine whether the * blocks to be read are part of a co-linear pair of existing prefetch * streams. If a set is found, coalesce the streams, removing one, and * configure the prefetch so it looks for a strided access pattern. * * In other words: if we find two sequential access streams that are * the same length and distance N appart, and this read is N from the * last stream, then we are probably in a strided access pattern. So * combine the two sequential streams into a single strided stream. * * If no co-linear streams are found, return NULL. */ static int dmu_zfetch_colinear(zfetch_t *zf, zstream_t *zh) { zstream_t *z_walk; zstream_t *z_comp; if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER)) return (0); if (zh == NULL) { rw_exit(&zf->zf_rwlock); return (0); } for (z_walk = list_head(&zf->zf_stream); z_walk; z_walk = list_next(&zf->zf_stream, z_walk)) { for (z_comp = list_next(&zf->zf_stream, z_walk); z_comp; z_comp = list_next(&zf->zf_stream, z_comp)) { int64_t diff; if (z_walk->zst_len != z_walk->zst_stride || z_comp->zst_len != z_comp->zst_stride) { continue; } diff = z_comp->zst_offset - z_walk->zst_offset; if (z_comp->zst_offset + diff == zh->zst_offset) { z_walk->zst_offset = zh->zst_offset; z_walk->zst_direction = diff < 0 ? -1 : 1; z_walk->zst_stride = diff * z_walk->zst_direction; z_walk->zst_ph_offset = zh->zst_offset + z_walk->zst_stride; dmu_zfetch_stream_remove(zf, z_comp); mutex_destroy(&z_comp->zst_lock); kmem_free(z_comp, sizeof (zstream_t)); dmu_zfetch_dofetch(zf, z_walk); rw_exit(&zf->zf_rwlock); return (1); } diff = z_walk->zst_offset - z_comp->zst_offset; if (z_walk->zst_offset + diff == zh->zst_offset) { z_walk->zst_offset = zh->zst_offset; z_walk->zst_direction = diff < 0 ? -1 : 1; z_walk->zst_stride = diff * z_walk->zst_direction; z_walk->zst_ph_offset = zh->zst_offset + z_walk->zst_stride; dmu_zfetch_stream_remove(zf, z_comp); mutex_destroy(&z_comp->zst_lock); kmem_free(z_comp, sizeof (zstream_t)); dmu_zfetch_dofetch(zf, z_walk); rw_exit(&zf->zf_rwlock); return (1); } } } rw_exit(&zf->zf_rwlock); return (0); } /* * Given a zstream_t, determine the bounds of the prefetch. Then call the * routine that actually prefetches the individual blocks. */ static void dmu_zfetch_dofetch(zfetch_t *zf, zstream_t *zs) { uint64_t prefetch_tail; uint64_t prefetch_limit; uint64_t prefetch_ofst; uint64_t prefetch_len; uint64_t blocks_fetched; zs->zst_stride = MAX((int64_t)zs->zst_stride, zs->zst_len); zs->zst_cap = MIN(zfetch_block_cap, 2 * zs->zst_cap); prefetch_tail = MAX((int64_t)zs->zst_ph_offset, (int64_t)(zs->zst_offset + zs->zst_stride)); /* * XXX: use a faster division method? */ prefetch_limit = zs->zst_offset + zs->zst_len + (zs->zst_cap * zs->zst_stride) / zs->zst_len; while (prefetch_tail < prefetch_limit) { prefetch_ofst = zs->zst_offset + zs->zst_direction * (prefetch_tail - zs->zst_offset); prefetch_len = zs->zst_len; /* * Don't prefetch beyond the end of the file, if working * backwards. */ if ((zs->zst_direction == ZFETCH_BACKWARD) && (prefetch_ofst > prefetch_tail)) { prefetch_len += prefetch_ofst; prefetch_ofst = 0; } /* don't prefetch more than we're supposed to */ if (prefetch_len > zs->zst_len) break; blocks_fetched = dmu_zfetch_fetch(zf->zf_dnode, prefetch_ofst, zs->zst_len); prefetch_tail += zs->zst_stride; /* stop if we've run out of stuff to prefetch */ if (blocks_fetched < zs->zst_len) break; } zs->zst_ph_offset = prefetch_tail; zs->zst_last = lbolt; } /* * This takes a pointer to a zfetch structure and a dnode. It performs the * necessary setup for the zfetch structure, grokking data from the * associated dnode. */ void dmu_zfetch_init(zfetch_t *zf, dnode_t *dno) { zf->zf_dnode = dno; zf->zf_stream_cnt = 0; zf->zf_alloc_fail = 0; } /* * Clean-up state associated with a zfetch structure. This frees allocated * structure members, empties the zf_stream tree, and generally makes things * nice. This doesn't free the zfetch_t itself, that's left to the caller. */ void dmu_zfetch_rele(zfetch_t *zf) { zstream_t *zs; zstream_t *zs_next; for (zs = list_head(&zf->zf_stream); zs; zs = zs_next) { zs_next = list_next(&zf->zf_stream, zs); list_remove(&zf->zf_stream, zs); mutex_destroy(&zs->zst_lock); kmem_free(zs, sizeof (zstream_t)); } } /* * Construct a zfetch structure. */ void dmu_zfetch_cons(zfetch_t *zf) { list_create(&zf->zf_stream, sizeof (zstream_t), offsetof(zstream_t, zst_node)); rw_init(&zf->zf_rwlock, NULL, RW_DEFAULT, NULL); } /* * Destruct a zfetch structure. */ void dmu_zfetch_dest(zfetch_t *zf) { list_destroy(&zf->zf_stream); rw_destroy(&zf->zf_rwlock); } /* * This function computes the actual size, in blocks, that can be prefetched, * and fetches it. */ static uint64_t dmu_zfetch_fetch(dnode_t *dn, uint64_t blkid, uint64_t nblks) { uint64_t fetchsz; uint64_t i; fetchsz = dmu_zfetch_fetchsz(dn, blkid, nblks); for (i = 0; i < fetchsz; i++) { dbuf_prefetch(dn, blkid + i); } return (fetchsz); } /* * this function returns the number of blocks that would be prefetched, based * upon the supplied dnode, blockid, and nblks. This is used so that we can * update streams in place, and then prefetch with their old value after the * fact. This way, we can delay the prefetch, but subsequent accesses to the * stream won't result in the same data being prefetched multiple times. */ static uint64_t dmu_zfetch_fetchsz(dnode_t *dn, uint64_t blkid, uint64_t nblks) { uint64_t fetchsz; if (blkid > dn->dn_maxblkid) { return (0); } /* compute fetch size */ if (blkid + nblks + 1 > dn->dn_maxblkid) { fetchsz = (dn->dn_maxblkid - blkid) + 1; ASSERT(blkid + fetchsz - 1 <= dn->dn_maxblkid); } else { fetchsz = nblks; } return (fetchsz); } /* * given a zfetch and a zsearch structure, see if there is an associated zstream * for this block read. If so, it starts a prefetch for the stream it * located and returns true, otherwise it returns false */ static int dmu_zfetch_find(zfetch_t *zf, zstream_t *zh, int prefetched) { zstream_t *zs; int64_t diff; int reset = !prefetched; int rc = 0; if (zh == NULL) return (0); /* * XXX: This locking strategy is a bit coarse; however, it's impact has * yet to be tested. If this turns out to be an issue, it can be * modified in a number of different ways. */ rw_enter(&zf->zf_rwlock, RW_READER); top: for (zs = list_head(&zf->zf_stream); zs; zs = list_next(&zf->zf_stream, zs)) { /* * XXX - should this be an assert? */ if (zs->zst_len == 0) { /* bogus stream */ continue; } /* * We hit this case when we are in a strided prefetch stream: * we will read "len" blocks before "striding". */ if (zh->zst_offset >= zs->zst_offset && zh->zst_offset < zs->zst_offset + zs->zst_len) { /* already fetched */ rc = 1; goto out; } /* * This is the forward sequential read case: we increment * len by one each time we hit here, so we will enter this * case on every read. */ if (zh->zst_offset == zs->zst_offset + zs->zst_len) { reset = !prefetched && zs->zst_len > 1; mutex_enter(&zs->zst_lock); if (zh->zst_offset != zs->zst_offset + zs->zst_len) { mutex_exit(&zs->zst_lock); goto top; } zs->zst_len += zh->zst_len; diff = zs->zst_len - zfetch_block_cap; if (diff > 0) { zs->zst_offset += diff; zs->zst_len = zs->zst_len > diff ? zs->zst_len - diff : 0; } zs->zst_direction = ZFETCH_FORWARD; break; /* * Same as above, but reading backwards through the file. */ } else if (zh->zst_offset == zs->zst_offset - zh->zst_len) { /* backwards sequential access */ reset = !prefetched && zs->zst_len > 1; mutex_enter(&zs->zst_lock); if (zh->zst_offset != zs->zst_offset - zh->zst_len) { mutex_exit(&zs->zst_lock); goto top; } zs->zst_offset = zs->zst_offset > zh->zst_len ? zs->zst_offset - zh->zst_len : 0; zs->zst_ph_offset = zs->zst_ph_offset > zh->zst_len ? zs->zst_ph_offset - zh->zst_len : 0; zs->zst_len += zh->zst_len; diff = zs->zst_len - zfetch_block_cap; if (diff > 0) { zs->zst_ph_offset = zs->zst_ph_offset > diff ? zs->zst_ph_offset - diff : 0; zs->zst_len = zs->zst_len > diff ? zs->zst_len - diff : zs->zst_len; } zs->zst_direction = ZFETCH_BACKWARD; break; } else if ((zh->zst_offset - zs->zst_offset - zs->zst_stride < zs->zst_len) && (zs->zst_len != zs->zst_stride)) { /* strided forward access */ mutex_enter(&zs->zst_lock); if ((zh->zst_offset - zs->zst_offset - zs->zst_stride >= zs->zst_len) || (zs->zst_len == zs->zst_stride)) { mutex_exit(&zs->zst_lock); goto top; } zs->zst_offset += zs->zst_stride; zs->zst_direction = ZFETCH_FORWARD; break; } else if ((zh->zst_offset - zs->zst_offset + zs->zst_stride < zs->zst_len) && (zs->zst_len != zs->zst_stride)) { /* strided reverse access */ mutex_enter(&zs->zst_lock); if ((zh->zst_offset - zs->zst_offset + zs->zst_stride >= zs->zst_len) || (zs->zst_len == zs->zst_stride)) { mutex_exit(&zs->zst_lock); goto top; } zs->zst_offset = zs->zst_offset > zs->zst_stride ? zs->zst_offset - zs->zst_stride : 0; zs->zst_ph_offset = (zs->zst_ph_offset > (2 * zs->zst_stride)) ? (zs->zst_ph_offset - (2 * zs->zst_stride)) : 0; zs->zst_direction = ZFETCH_BACKWARD; break; } } if (zs) { if (reset) { zstream_t *rm = zs; rc = 0; mutex_exit(&zs->zst_lock); rw_exit(&zf->zf_rwlock); rw_enter(&zf->zf_rwlock, RW_WRITER); /* * Relocate the stream, in case someone removes * it while we were acquiring the WRITER lock. */ for (zs = list_head(&zf->zf_stream); zs; zs = list_next(&zf->zf_stream, zs)) { if (zs == rm) { dmu_zfetch_stream_remove(zf, zs); mutex_destroy(&zs->zst_lock); kmem_free(zs, sizeof (zstream_t)); break; } } } else { rc = 1; dmu_zfetch_dofetch(zf, zs); mutex_exit(&zs->zst_lock); } } out: rw_exit(&zf->zf_rwlock); return (rc); } /* * Given a zfetch and zstream structure, insert the zstream structure into the * AVL tree contained within the zfetch structure. Peform the appropriate * book-keeping. It is possible that another thread has inserted a stream which * matches one that we are about to insert, so we must be sure to check for this * case. If one is found, return failure, and let the caller cleanup the * duplicates. */ static int dmu_zfetch_stream_insert(zfetch_t *zf, zstream_t *zs) { zstream_t *zs_walk; zstream_t *zs_next; ASSERT(RW_WRITE_HELD(&zf->zf_rwlock)); for (zs_walk = list_head(&zf->zf_stream); zs_walk; zs_walk = zs_next) { zs_next = list_next(&zf->zf_stream, zs_walk); if (dmu_zfetch_streams_equal(zs_walk, zs)) { return (0); } } list_insert_head(&zf->zf_stream, zs); zf->zf_stream_cnt++; return (1); } /* * Walk the list of zstreams in the given zfetch, find an old one (by time), and * reclaim it for use by the caller. */ static zstream_t * dmu_zfetch_stream_reclaim(zfetch_t *zf) { zstream_t *zs; if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER)) return (0); for (zs = list_head(&zf->zf_stream); zs; zs = list_next(&zf->zf_stream, zs)) { if (((lbolt - zs->zst_last) / hz) > zfetch_min_sec_reap) break; } if (zs) { dmu_zfetch_stream_remove(zf, zs); mutex_destroy(&zs->zst_lock); bzero(zs, sizeof (zstream_t)); } else { zf->zf_alloc_fail++; } rw_exit(&zf->zf_rwlock); return (zs); } /* * Given a zfetch and zstream structure, remove the zstream structure from its * container in the zfetch structure. Perform the appropriate book-keeping. */ static void dmu_zfetch_stream_remove(zfetch_t *zf, zstream_t *zs) { ASSERT(RW_WRITE_HELD(&zf->zf_rwlock)); list_remove(&zf->zf_stream, zs); zf->zf_stream_cnt--; } static int dmu_zfetch_streams_equal(zstream_t *zs1, zstream_t *zs2) { if (zs1->zst_offset != zs2->zst_offset) return (0); if (zs1->zst_len != zs2->zst_len) return (0); if (zs1->zst_stride != zs2->zst_stride) return (0); if (zs1->zst_ph_offset != zs2->zst_ph_offset) return (0); if (zs1->zst_cap != zs2->zst_cap) return (0); if (zs1->zst_direction != zs2->zst_direction) return (0); return (1); } /* * This is the prefetch entry point. It calls all of the other dmu_zfetch * routines to create, delete, find, or operate upon prefetch streams. */ void dmu_zfetch(zfetch_t *zf, uint64_t offset, uint64_t size, int prefetched) { zstream_t zst; zstream_t *newstream; int fetched; int inserted; unsigned int blkshft; uint64_t blksz; if (zfs_prefetch_disable) return; /* files that aren't ln2 blocksz are only one block -- nothing to do */ if (!zf->zf_dnode->dn_datablkshift) return; /* convert offset and size, into blockid and nblocks */ blkshft = zf->zf_dnode->dn_datablkshift; blksz = (1 << blkshft); bzero(&zst, sizeof (zstream_t)); zst.zst_offset = offset >> blkshft; zst.zst_len = (P2ROUNDUP(offset + size, blksz) - P2ALIGN(offset, blksz)) >> blkshft; fetched = dmu_zfetch_find(zf, &zst, prefetched); if (!fetched) { fetched = dmu_zfetch_colinear(zf, &zst); } if (!fetched) { newstream = dmu_zfetch_stream_reclaim(zf); /* * we still couldn't find a stream, drop the lock, and allocate * one if possible. Otherwise, give up and go home. */ if (newstream == NULL) { uint64_t maxblocks; uint32_t max_streams; uint32_t cur_streams; cur_streams = zf->zf_stream_cnt; maxblocks = zf->zf_dnode->dn_maxblkid; max_streams = MIN(zfetch_max_streams, (maxblocks / zfetch_block_cap)); if (max_streams == 0) { max_streams++; } if (cur_streams >= max_streams) { return; } newstream = kmem_zalloc(sizeof (zstream_t), KM_SLEEP); } newstream->zst_offset = zst.zst_offset; newstream->zst_len = zst.zst_len; newstream->zst_stride = zst.zst_len; newstream->zst_ph_offset = zst.zst_len + zst.zst_offset; newstream->zst_cap = zst.zst_len; newstream->zst_direction = ZFETCH_FORWARD; newstream->zst_last = lbolt; mutex_init(&newstream->zst_lock, NULL, MUTEX_DEFAULT, NULL); rw_enter(&zf->zf_rwlock, RW_WRITER); inserted = dmu_zfetch_stream_insert(zf, newstream); rw_exit(&zf->zf_rwlock); if (!inserted) { mutex_destroy(&newstream->zst_lock); kmem_free(newstream, sizeof (zstream_t)); } } }