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, 2015 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 kmutex_t mc_lock; 63 spa_t *mc_spa; 64 metaslab_group_t *mc_rotor; 65 metaslab_ops_t *mc_ops; 66 uint64_t mc_aliquot; 67 68 /* 69 * Track the number of metaslab groups that have been initialized 70 * and can accept allocations. An initialized metaslab group is 71 * one has been completely added to the config (i.e. we have 72 * updated the MOS config and the space has been added to the pool). 73 */ 74 uint64_t mc_groups; 75 76 /* 77 * Toggle to enable/disable the allocation throttle. 78 */ 79 boolean_t mc_alloc_throttle_enabled; 80 81 /* 82 * The allocation throttle works on a reservation system. Whenever 83 * an asynchronous zio wants to perform an allocation it must 84 * first reserve the number of blocks that it wants to allocate. 85 * If there aren't sufficient slots available for the pending zio 86 * then that I/O is throttled until more slots free up. The current 87 * number of reserved allocations is maintained by the mc_alloc_slots 88 * refcount. The mc_alloc_max_slots value determines the maximum 89 * number of allocations that the system allows. Gang blocks are 90 * allowed to reserve slots even if we've reached the maximum 91 * number of allocations allowed. 92 */ 93 uint64_t mc_alloc_max_slots; 94 refcount_t mc_alloc_slots; 95 96 uint64_t mc_alloc_groups; /* # of allocatable groups */ 97 98 uint64_t mc_alloc; /* total allocated space */ 99 uint64_t mc_deferred; /* total deferred frees */ 100 uint64_t mc_space; /* total space (alloc + free) */ 101 uint64_t mc_dspace; /* total deflated space */ 102 uint64_t mc_histogram[RANGE_TREE_HISTOGRAM_SIZE]; 103 }; 104 105 /* 106 * Metaslab groups encapsulate all the allocatable regions (i.e. metaslabs) 107 * of a top-level vdev. They are linked togther to form a circular linked 108 * list and can belong to only one metaslab class. Metaslab groups may become 109 * ineligible for allocations for a number of reasons such as limited free 110 * space, fragmentation, or going offline. When this happens the allocator will 111 * simply find the next metaslab group in the linked list and attempt 112 * to allocate from that group instead. 113 */ 114 struct metaslab_group { 115 kmutex_t mg_lock; 116 avl_tree_t mg_metaslab_tree; 117 uint64_t mg_aliquot; 118 boolean_t mg_allocatable; /* can we allocate? */ 119 120 /* 121 * A metaslab group is considered to be initialized only after 122 * we have updated the MOS config and added the space to the pool. 123 * We only allow allocation attempts to a metaslab group if it 124 * has been initialized. 125 */ 126 boolean_t mg_initialized; 127 128 uint64_t mg_free_capacity; /* percentage free */ 129 int64_t mg_bias; 130 int64_t mg_activation_count; 131 metaslab_class_t *mg_class; 132 vdev_t *mg_vd; 133 taskq_t *mg_taskq; 134 metaslab_group_t *mg_prev; 135 metaslab_group_t *mg_next; 136 137 /* 138 * Each metaslab group can handle mg_max_alloc_queue_depth allocations 139 * which are tracked by mg_alloc_queue_depth. It's possible for a 140 * metaslab group to handle more allocations than its max. This 141 * can occur when gang blocks are required or when other groups 142 * are unable to handle their share of allocations. 143 */ 144 uint64_t mg_max_alloc_queue_depth; 145 refcount_t mg_alloc_queue_depth; 146 147 /* 148 * A metalab group that can no longer allocate the minimum block 149 * size will set mg_no_free_space. Once a metaslab group is out 150 * of space then its share of work must be distributed to other 151 * groups. 152 */ 153 boolean_t mg_no_free_space; 154 155 uint64_t mg_allocations; 156 uint64_t mg_failed_allocations; 157 uint64_t mg_fragmentation; 158 uint64_t mg_histogram[RANGE_TREE_HISTOGRAM_SIZE]; 159 }; 160 161 /* 162 * This value defines the number of elements in the ms_lbas array. The value 163 * of 64 was chosen as it covers all power of 2 buckets up to UINT64_MAX. 164 * This is the equivalent of highbit(UINT64_MAX). 165 */ 166 #define MAX_LBAS 64 167 168 /* 169 * Each metaslab maintains a set of in-core trees to track metaslab operations. 170 * The in-core free tree (ms_tree) contains the current list of free segments. 171 * As blocks are allocated, the allocated segment are removed from the ms_tree 172 * and added to a per txg allocation tree (ms_alloctree). As blocks are freed, 173 * they are added to the per txg free tree (ms_freetree). These per txg 174 * trees allow us to process all allocations and frees in syncing context 175 * where it is safe to update the on-disk space maps. One additional in-core 176 * tree is maintained to track deferred frees (ms_defertree). Once a block 177 * is freed it will move from the ms_freetree to the ms_defertree. A deferred 178 * free means that a block has been freed but cannot be used by the pool 179 * until TXG_DEFER_SIZE transactions groups later. For example, a block 180 * that is freed in txg 50 will not be available for reallocation until 181 * txg 52 (50 + TXG_DEFER_SIZE). This provides a safety net for uberblock 182 * rollback. A pool could be safely rolled back TXG_DEFERS_SIZE 183 * transactions groups and ensure that no block has been reallocated. 184 * 185 * The simplified transition diagram looks like this: 186 * 187 * 188 * ALLOCATE 189 * | 190 * V 191 * free segment (ms_tree) --------> ms_alloctree ----> (write to space map) 192 * ^ 193 * | 194 * | ms_freetree <--- FREE 195 * | | 196 * | | 197 * | | 198 * +----------- ms_defertree <-------+---------> (write to space map) 199 * 200 * 201 * Each metaslab's space is tracked in a single space map in the MOS, 202 * which is only updated in syncing context. Each time we sync a txg, 203 * we append the allocs and frees from that txg to the space map. 204 * The pool space is only updated once all metaslabs have finished syncing. 205 * 206 * To load the in-core free tree we read the space map from disk. 207 * This object contains a series of alloc and free records that are 208 * combined to make up the list of all free segments in this metaslab. These 209 * segments are represented in-core by the ms_tree and are stored in an 210 * AVL tree. 211 * 212 * As the space map grows (as a result of the appends) it will 213 * eventually become space-inefficient. When the metaslab's in-core free tree 214 * is zfs_condense_pct/100 times the size of the minimal on-disk 215 * representation, we rewrite it in its minimized form. If a metaslab 216 * needs to condense then we must set the ms_condensing flag to ensure 217 * that allocations are not performed on the metaslab that is being written. 218 */ 219 struct metaslab { 220 kmutex_t ms_lock; 221 kcondvar_t ms_load_cv; 222 space_map_t *ms_sm; 223 metaslab_ops_t *ms_ops; 224 uint64_t ms_id; 225 uint64_t ms_start; 226 uint64_t ms_size; 227 uint64_t ms_fragmentation; 228 229 range_tree_t *ms_alloctree[TXG_SIZE]; 230 range_tree_t *ms_freetree[TXG_SIZE]; 231 range_tree_t *ms_defertree[TXG_DEFER_SIZE]; 232 range_tree_t *ms_tree; 233 234 boolean_t ms_condensing; /* condensing? */ 235 boolean_t ms_condense_wanted; 236 boolean_t ms_loaded; 237 boolean_t ms_loading; 238 239 int64_t ms_deferspace; /* sum of ms_defermap[] space */ 240 uint64_t ms_weight; /* weight vs. others in group */ 241 uint64_t ms_access_txg; 242 243 /* 244 * The metaslab block allocators can optionally use a size-ordered 245 * range tree and/or an array of LBAs. Not all allocators use 246 * this functionality. The ms_size_tree should always contain the 247 * same number of segments as the ms_tree. The only difference 248 * is that the ms_size_tree is ordered by segment sizes. 249 */ 250 avl_tree_t ms_size_tree; 251 uint64_t ms_lbas[MAX_LBAS]; 252 253 metaslab_group_t *ms_group; /* metaslab group */ 254 avl_node_t ms_group_node; /* node in metaslab group tree */ 255 txg_node_t ms_txg_node; /* per-txg dirty metaslab links */ 256 }; 257 258 #ifdef __cplusplus 259 } 260 #endif 261 262 #endif /* _SYS_METASLAB_IMPL_H */ 263