1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 /* 22 * Copyright 2009 Sun Microsystems, Inc. All rights reserved. 23 * Use is subject to license terms. 24 */ 25 26 /* 27 * Copyright (c) 2011, 2014 by Delphix. All rights reserved. 28 */ 29 30 #ifndef _SYS_METASLAB_IMPL_H 31 #define _SYS_METASLAB_IMPL_H 32 33 #include <sys/metaslab.h> 34 #include <sys/space_map.h> 35 #include <sys/range_tree.h> 36 #include <sys/vdev.h> 37 #include <sys/txg.h> 38 #include <sys/avl.h> 39 40 #ifdef __cplusplus 41 extern "C" { 42 #endif 43 44 /* 45 * A metaslab class encompasses a category of allocatable top-level vdevs. 46 * Each top-level vdev is associated with a metaslab group which defines 47 * the allocatable region for that vdev. Examples of these categories include 48 * "normal" for data block allocations (i.e. main pool allocations) or "log" 49 * for allocations designated for intent log devices (i.e. slog devices). 50 * When a block allocation is requested from the SPA it is associated with a 51 * metaslab_class_t, and only top-level vdevs (i.e. metaslab groups) belonging 52 * to the class can be used to satisfy that request. Allocations are done 53 * by traversing the metaslab groups that are linked off of the mc_rotor field. 54 * This rotor points to the next metaslab group where allocations will be 55 * attempted. Allocating a block is a 3 step process -- select the metaslab 56 * group, select the metaslab, and then allocate the block. The metaslab 57 * class defines the low-level block allocator that will be used as the 58 * final step in allocation. These allocators are pluggable allowing each class 59 * to use a block allocator that best suits that class. 60 */ 61 struct metaslab_class { 62 spa_t *mc_spa; 63 metaslab_group_t *mc_rotor; 64 metaslab_ops_t *mc_ops; 65 uint64_t mc_aliquot; 66 uint64_t mc_alloc_groups; /* # of allocatable groups */ 67 uint64_t mc_alloc; /* total allocated space */ 68 uint64_t mc_deferred; /* total deferred frees */ 69 uint64_t mc_space; /* total space (alloc + free) */ 70 uint64_t mc_dspace; /* total deflated space */ 71 uint64_t mc_histogram[RANGE_TREE_HISTOGRAM_SIZE]; 72 }; 73 74 /* 75 * Metaslab groups encapsulate all the allocatable regions (i.e. metaslabs) 76 * of a top-level vdev. They are linked togther to form a circular linked 77 * list and can belong to only one metaslab class. Metaslab groups may become 78 * ineligible for allocations for a number of reasons such as limited free 79 * space, fragmentation, or going offline. When this happens the allocator will 80 * simply find the next metaslab group in the linked list and attempt 81 * to allocate from that group instead. 82 */ 83 struct metaslab_group { 84 kmutex_t mg_lock; 85 avl_tree_t mg_metaslab_tree; 86 uint64_t mg_aliquot; 87 boolean_t mg_allocatable; /* can we allocate? */ 88 uint64_t mg_free_capacity; /* percentage free */ 89 int64_t mg_bias; 90 int64_t mg_activation_count; 91 metaslab_class_t *mg_class; 92 vdev_t *mg_vd; 93 taskq_t *mg_taskq; 94 metaslab_group_t *mg_prev; 95 metaslab_group_t *mg_next; 96 uint64_t mg_fragmentation; 97 uint64_t mg_histogram[RANGE_TREE_HISTOGRAM_SIZE]; 98 }; 99 100 /* 101 * This value defines the number of elements in the ms_lbas array. The value 102 * of 64 was chosen as it covers all power of 2 buckets up to UINT64_MAX. 103 * This is the equivalent of highbit(UINT64_MAX). 104 */ 105 #define MAX_LBAS 64 106 107 /* 108 * Each metaslab maintains a set of in-core trees to track metaslab operations. 109 * The in-core free tree (ms_tree) contains the current list of free segments. 110 * As blocks are allocated, the allocated segment are removed from the ms_tree 111 * and added to a per txg allocation tree (ms_alloctree). As blocks are freed, 112 * they are added to the per txg free tree (ms_freetree). These per txg 113 * trees allow us to process all allocations and frees in syncing context 114 * where it is safe to update the on-disk space maps. One additional in-core 115 * tree is maintained to track deferred frees (ms_defertree). Once a block 116 * is freed it will move from the ms_freetree to the ms_defertree. A deferred 117 * free means that a block has been freed but cannot be used by the pool 118 * until TXG_DEFER_SIZE transactions groups later. For example, a block 119 * that is freed in txg 50 will not be available for reallocation until 120 * txg 52 (50 + TXG_DEFER_SIZE). This provides a safety net for uberblock 121 * rollback. A pool could be safely rolled back TXG_DEFERS_SIZE 122 * transactions groups and ensure that no block has been reallocated. 123 * 124 * The simplified transition diagram looks like this: 125 * 126 * 127 * ALLOCATE 128 * | 129 * V 130 * free segment (ms_tree) --------> ms_alloctree ----> (write to space map) 131 * ^ 132 * | 133 * | ms_freetree <--- FREE 134 * | | 135 * | | 136 * | | 137 * +----------- ms_defertree <-------+---------> (write to space map) 138 * 139 * 140 * Each metaslab's space is tracked in a single space map in the MOS, 141 * which is only updated in syncing context. Each time we sync a txg, 142 * we append the allocs and frees from that txg to the space map. 143 * The pool space is only updated once all metaslabs have finished syncing. 144 * 145 * To load the in-core free tree we read the space map from disk. 146 * This object contains a series of alloc and free records that are 147 * combined to make up the list of all free segments in this metaslab. These 148 * segments are represented in-core by the ms_tree and are stored in an 149 * AVL tree. 150 * 151 * As the space map grows (as a result of the appends) it will 152 * eventually become space-inefficient. When the metaslab's in-core free tree 153 * is zfs_condense_pct/100 times the size of the minimal on-disk 154 * representation, we rewrite it in its minimized form. If a metaslab 155 * needs to condense then we must set the ms_condensing flag to ensure 156 * that allocations are not performed on the metaslab that is being written. 157 */ 158 struct metaslab { 159 kmutex_t ms_lock; 160 kcondvar_t ms_load_cv; 161 space_map_t *ms_sm; 162 metaslab_ops_t *ms_ops; 163 uint64_t ms_id; 164 uint64_t ms_start; 165 uint64_t ms_size; 166 uint64_t ms_fragmentation; 167 168 range_tree_t *ms_alloctree[TXG_SIZE]; 169 range_tree_t *ms_freetree[TXG_SIZE]; 170 range_tree_t *ms_defertree[TXG_DEFER_SIZE]; 171 range_tree_t *ms_tree; 172 173 boolean_t ms_condensing; /* condensing? */ 174 boolean_t ms_condense_wanted; 175 boolean_t ms_loaded; 176 boolean_t ms_loading; 177 178 int64_t ms_deferspace; /* sum of ms_defermap[] space */ 179 uint64_t ms_weight; /* weight vs. others in group */ 180 uint64_t ms_access_txg; 181 182 /* 183 * The metaslab block allocators can optionally use a size-ordered 184 * range tree and/or an array of LBAs. Not all allocators use 185 * this functionality. The ms_size_tree should always contain the 186 * same number of segments as the ms_tree. The only difference 187 * is that the ms_size_tree is ordered by segment sizes. 188 */ 189 avl_tree_t ms_size_tree; 190 uint64_t ms_lbas[MAX_LBAS]; 191 192 metaslab_group_t *ms_group; /* metaslab group */ 193 avl_node_t ms_group_node; /* node in metaslab group tree */ 194 txg_node_t ms_txg_node; /* per-txg dirty metaslab links */ 195 }; 196 197 #ifdef __cplusplus 198 } 199 #endif 200 201 #endif /* _SYS_METASLAB_IMPL_H */ 202