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 * Metaslab allocation tracing record. 46 */ 47 typedef struct metaslab_alloc_trace { 48 list_node_t mat_list_node; 49 metaslab_group_t *mat_mg; 50 metaslab_t *mat_msp; 51 uint64_t mat_size; 52 uint64_t mat_weight; 53 uint32_t mat_dva_id; 54 uint64_t mat_offset; 55 } metaslab_alloc_trace_t; 56 57 /* 58 * Used by the metaslab allocation tracing facility to indicate 59 * error conditions. These errors are stored to the offset member 60 * of the metaslab_alloc_trace_t record and displayed by mdb. 61 */ 62 typedef enum trace_alloc_type { 63 TRACE_ALLOC_FAILURE = -1ULL, 64 TRACE_TOO_SMALL = -2ULL, 65 TRACE_FORCE_GANG = -3ULL, 66 TRACE_NOT_ALLOCATABLE = -4ULL, 67 TRACE_GROUP_FAILURE = -5ULL, 68 TRACE_ENOSPC = -6ULL, 69 TRACE_CONDENSING = -7ULL, 70 TRACE_VDEV_ERROR = -8ULL 71 } trace_alloc_type_t; 72 73 #define METASLAB_WEIGHT_PRIMARY (1ULL << 63) 74 #define METASLAB_WEIGHT_SECONDARY (1ULL << 62) 75 #define METASLAB_WEIGHT_TYPE (1ULL << 61) 76 #define METASLAB_ACTIVE_MASK \ 77 (METASLAB_WEIGHT_PRIMARY | METASLAB_WEIGHT_SECONDARY) 78 79 /* 80 * The metaslab weight is used to encode the amount of free space in a 81 * metaslab, such that the "best" metaslab appears first when sorting the 82 * metaslabs by weight. The weight (and therefore the "best" metaslab) can 83 * be determined in two different ways: by computing a weighted sum of all 84 * the free space in the metaslab (a space based weight) or by counting only 85 * the free segments of the largest size (a segment based weight). We prefer 86 * the segment based weight because it reflects how the free space is 87 * comprised, but we cannot always use it -- legacy pools do not have the 88 * space map histogram information necessary to determine the largest 89 * contiguous regions. Pools that have the space map histogram determine 90 * the segment weight by looking at each bucket in the histogram and 91 * determining the free space whose size in bytes is in the range: 92 * [2^i, 2^(i+1)) 93 * We then encode the largest index, i, that contains regions into the 94 * segment-weighted value. 95 * 96 * Space-based weight: 97 * 98 * 64 56 48 40 32 24 16 8 0 99 * +-------+-------+-------+-------+-------+-------+-------+-------+ 100 * |PS1| weighted-free space | 101 * +-------+-------+-------+-------+-------+-------+-------+-------+ 102 * 103 * PS - indicates primary and secondary activation 104 * space - the fragmentation-weighted space 105 * 106 * Segment-based weight: 107 * 108 * 64 56 48 40 32 24 16 8 0 109 * +-------+-------+-------+-------+-------+-------+-------+-------+ 110 * |PS0| idx| count of segments in region | 111 * +-------+-------+-------+-------+-------+-------+-------+-------+ 112 * 113 * PS - indicates primary and secondary activation 114 * idx - index for the highest bucket in the histogram 115 * count - number of segments in the specified bucket 116 */ 117 #define WEIGHT_GET_ACTIVE(weight) BF64_GET((weight), 62, 2) 118 #define WEIGHT_SET_ACTIVE(weight, x) BF64_SET((weight), 62, 2, x) 119 120 #define WEIGHT_IS_SPACEBASED(weight) \ 121 ((weight) == 0 || BF64_GET((weight), 61, 1)) 122 #define WEIGHT_SET_SPACEBASED(weight) BF64_SET((weight), 61, 1, 1) 123 124 /* 125 * These macros are only applicable to segment-based weighting. 126 */ 127 #define WEIGHT_GET_INDEX(weight) BF64_GET((weight), 55, 6) 128 #define WEIGHT_SET_INDEX(weight, x) BF64_SET((weight), 55, 6, x) 129 #define WEIGHT_GET_COUNT(weight) BF64_GET((weight), 0, 55) 130 #define WEIGHT_SET_COUNT(weight, x) BF64_SET((weight), 0, 55, x) 131 132 /* 133 * A metaslab class encompasses a category of allocatable top-level vdevs. 134 * Each top-level vdev is associated with a metaslab group which defines 135 * the allocatable region for that vdev. Examples of these categories include 136 * "normal" for data block allocations (i.e. main pool allocations) or "log" 137 * for allocations designated for intent log devices (i.e. slog devices). 138 * When a block allocation is requested from the SPA it is associated with a 139 * metaslab_class_t, and only top-level vdevs (i.e. metaslab groups) belonging 140 * to the class can be used to satisfy that request. Allocations are done 141 * by traversing the metaslab groups that are linked off of the mc_rotor field. 142 * This rotor points to the next metaslab group where allocations will be 143 * attempted. Allocating a block is a 3 step process -- select the metaslab 144 * group, select the metaslab, and then allocate the block. The metaslab 145 * class defines the low-level block allocator that will be used as the 146 * final step in allocation. These allocators are pluggable allowing each class 147 * to use a block allocator that best suits that class. 148 */ 149 struct metaslab_class { 150 kmutex_t mc_lock; 151 spa_t *mc_spa; 152 metaslab_group_t *mc_rotor; 153 metaslab_ops_t *mc_ops; 154 uint64_t mc_aliquot; 155 156 /* 157 * Track the number of metaslab groups that have been initialized 158 * and can accept allocations. An initialized metaslab group is 159 * one has been completely added to the config (i.e. we have 160 * updated the MOS config and the space has been added to the pool). 161 */ 162 uint64_t mc_groups; 163 164 /* 165 * Toggle to enable/disable the allocation throttle. 166 */ 167 boolean_t mc_alloc_throttle_enabled; 168 169 /* 170 * The allocation throttle works on a reservation system. Whenever 171 * an asynchronous zio wants to perform an allocation it must 172 * first reserve the number of blocks that it wants to allocate. 173 * If there aren't sufficient slots available for the pending zio 174 * then that I/O is throttled until more slots free up. The current 175 * number of reserved allocations is maintained by the mc_alloc_slots 176 * refcount. The mc_alloc_max_slots value determines the maximum 177 * number of allocations that the system allows. Gang blocks are 178 * allowed to reserve slots even if we've reached the maximum 179 * number of allocations allowed. 180 */ 181 uint64_t mc_alloc_max_slots; 182 refcount_t mc_alloc_slots; 183 184 uint64_t mc_alloc_groups; /* # of allocatable groups */ 185 186 uint64_t mc_alloc; /* total allocated space */ 187 uint64_t mc_deferred; /* total deferred frees */ 188 uint64_t mc_space; /* total space (alloc + free) */ 189 uint64_t mc_dspace; /* total deflated space */ 190 uint64_t mc_histogram[RANGE_TREE_HISTOGRAM_SIZE]; 191 }; 192 193 /* 194 * Metaslab groups encapsulate all the allocatable regions (i.e. metaslabs) 195 * of a top-level vdev. They are linked togther to form a circular linked 196 * list and can belong to only one metaslab class. Metaslab groups may become 197 * ineligible for allocations for a number of reasons such as limited free 198 * space, fragmentation, or going offline. When this happens the allocator will 199 * simply find the next metaslab group in the linked list and attempt 200 * to allocate from that group instead. 201 */ 202 struct metaslab_group { 203 kmutex_t mg_lock; 204 avl_tree_t mg_metaslab_tree; 205 uint64_t mg_aliquot; 206 boolean_t mg_allocatable; /* can we allocate? */ 207 208 /* 209 * A metaslab group is considered to be initialized only after 210 * we have updated the MOS config and added the space to the pool. 211 * We only allow allocation attempts to a metaslab group if it 212 * has been initialized. 213 */ 214 boolean_t mg_initialized; 215 216 uint64_t mg_free_capacity; /* percentage free */ 217 int64_t mg_bias; 218 int64_t mg_activation_count; 219 metaslab_class_t *mg_class; 220 vdev_t *mg_vd; 221 taskq_t *mg_taskq; 222 metaslab_group_t *mg_prev; 223 metaslab_group_t *mg_next; 224 225 /* 226 * Each metaslab group can handle mg_max_alloc_queue_depth allocations 227 * which are tracked by mg_alloc_queue_depth. It's possible for a 228 * metaslab group to handle more allocations than its max. This 229 * can occur when gang blocks are required or when other groups 230 * are unable to handle their share of allocations. 231 */ 232 uint64_t mg_max_alloc_queue_depth; 233 refcount_t mg_alloc_queue_depth; 234 235 /* 236 * A metalab group that can no longer allocate the minimum block 237 * size will set mg_no_free_space. Once a metaslab group is out 238 * of space then its share of work must be distributed to other 239 * groups. 240 */ 241 boolean_t mg_no_free_space; 242 243 uint64_t mg_allocations; 244 uint64_t mg_failed_allocations; 245 uint64_t mg_fragmentation; 246 uint64_t mg_histogram[RANGE_TREE_HISTOGRAM_SIZE]; 247 }; 248 249 /* 250 * This value defines the number of elements in the ms_lbas array. The value 251 * of 64 was chosen as it covers all power of 2 buckets up to UINT64_MAX. 252 * This is the equivalent of highbit(UINT64_MAX). 253 */ 254 #define MAX_LBAS 64 255 256 /* 257 * Each metaslab maintains a set of in-core trees to track metaslab 258 * operations. The in-core free tree (ms_tree) contains the list of 259 * free segments which are eligible for allocation. As blocks are 260 * allocated, the allocated segments are removed from the ms_tree and 261 * added to a per txg allocation tree (ms_alloctree). This allows us to 262 * process all allocations in syncing context where it is safe to update 263 * the on-disk space maps. Frees are also processed in syncing context. 264 * Most frees are generated from syncing context, and those that are not 265 * are held in the spa_free_bplist for processing in syncing context. 266 * An additional set of in-core trees is maintained to track deferred 267 * frees (ms_defertree). Once a block is freed it will move from the 268 * ms_freedtree to the ms_defertree. A deferred free means that a block 269 * has been freed but cannot be used by the pool until TXG_DEFER_SIZE 270 * transactions groups later. For example, a block that is freed in txg 271 * 50 will not be available for reallocation until txg 52 (50 + 272 * TXG_DEFER_SIZE). This provides a safety net for uberblock rollback. 273 * A pool could be safely rolled back TXG_DEFERS_SIZE transactions 274 * groups and ensure that no block has been reallocated. 275 * 276 * The simplified transition diagram looks like this: 277 * 278 * 279 * ALLOCATE 280 * | 281 * V 282 * free segment (ms_tree) -----> ms_alloctree[4] ----> (write to space map) 283 * ^ 284 * | ms_freeingtree <--- FREE 285 * | | 286 * | v 287 * | ms_freedtree 288 * | | 289 * +-------- ms_defertree[2] <-------+---------> (write to space map) 290 * 291 * 292 * Each metaslab's space is tracked in a single space map in the MOS, 293 * which is only updated in syncing context. Each time we sync a txg, 294 * we append the allocs and frees from that txg to the space map. The 295 * pool space is only updated once all metaslabs have finished syncing. 296 * 297 * To load the in-core free tree we read the space map from disk. This 298 * object contains a series of alloc and free records that are combined 299 * to make up the list of all free segments in this metaslab. These 300 * segments are represented in-core by the ms_tree and are stored in an 301 * AVL tree. 302 * 303 * As the space map grows (as a result of the appends) it will 304 * eventually become space-inefficient. When the metaslab's in-core 305 * free tree is zfs_condense_pct/100 times the size of the minimal 306 * on-disk representation, we rewrite it in its minimized form. If a 307 * metaslab needs to condense then we must set the ms_condensing flag to 308 * ensure that allocations are not performed on the metaslab that is 309 * being written. 310 */ 311 struct metaslab { 312 kmutex_t ms_lock; 313 kcondvar_t ms_load_cv; 314 space_map_t *ms_sm; 315 uint64_t ms_id; 316 uint64_t ms_start; 317 uint64_t ms_size; 318 uint64_t ms_fragmentation; 319 320 range_tree_t *ms_alloctree[TXG_SIZE]; 321 range_tree_t *ms_tree; 322 323 /* 324 * The following range trees are accessed only from syncing context. 325 * ms_free*tree only have entries while syncing, and are empty 326 * between syncs. 327 */ 328 range_tree_t *ms_freeingtree; /* to free this syncing txg */ 329 range_tree_t *ms_freedtree; /* already freed this syncing txg */ 330 range_tree_t *ms_defertree[TXG_DEFER_SIZE]; 331 332 boolean_t ms_condensing; /* condensing? */ 333 boolean_t ms_condense_wanted; 334 335 /* 336 * We must hold both ms_lock and ms_group->mg_lock in order to 337 * modify ms_loaded. 338 */ 339 boolean_t ms_loaded; 340 boolean_t ms_loading; 341 342 int64_t ms_deferspace; /* sum of ms_defermap[] space */ 343 uint64_t ms_weight; /* weight vs. others in group */ 344 uint64_t ms_activation_weight; /* activation weight */ 345 346 /* 347 * Track of whenever a metaslab is selected for loading or allocation. 348 * We use this value to determine how long the metaslab should 349 * stay cached. 350 */ 351 uint64_t ms_selected_txg; 352 353 uint64_t ms_alloc_txg; /* last successful alloc (debug only) */ 354 uint64_t ms_max_size; /* maximum allocatable size */ 355 356 /* 357 * The metaslab block allocators can optionally use a size-ordered 358 * range tree and/or an array of LBAs. Not all allocators use 359 * this functionality. The ms_size_tree should always contain the 360 * same number of segments as the ms_tree. The only difference 361 * is that the ms_size_tree is ordered by segment sizes. 362 */ 363 avl_tree_t ms_size_tree; 364 uint64_t ms_lbas[MAX_LBAS]; 365 366 metaslab_group_t *ms_group; /* metaslab group */ 367 avl_node_t ms_group_node; /* node in metaslab group tree */ 368 txg_node_t ms_txg_node; /* per-txg dirty metaslab links */ 369 }; 370 371 #ifdef __cplusplus 372 } 373 #endif 374 375 #endif /* _SYS_METASLAB_IMPL_H */ 376