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, 2018 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 int mat_allocator; 56 } metaslab_alloc_trace_t; 57 58 /* 59 * Used by the metaslab allocation tracing facility to indicate 60 * error conditions. These errors are stored to the offset member 61 * of the metaslab_alloc_trace_t record and displayed by mdb. 62 */ 63 typedef enum trace_alloc_type { 64 TRACE_ALLOC_FAILURE = -1ULL, 65 TRACE_TOO_SMALL = -2ULL, 66 TRACE_FORCE_GANG = -3ULL, 67 TRACE_NOT_ALLOCATABLE = -4ULL, 68 TRACE_GROUP_FAILURE = -5ULL, 69 TRACE_ENOSPC = -6ULL, 70 TRACE_CONDENSING = -7ULL, 71 TRACE_VDEV_ERROR = -8ULL, 72 TRACE_INITIALIZING = -9ULL 73 } trace_alloc_type_t; 74 75 #define METASLAB_WEIGHT_PRIMARY (1ULL << 63) 76 #define METASLAB_WEIGHT_SECONDARY (1ULL << 62) 77 #define METASLAB_WEIGHT_CLAIM (1ULL << 61) 78 #define METASLAB_WEIGHT_TYPE (1ULL << 60) 79 #define METASLAB_ACTIVE_MASK \ 80 (METASLAB_WEIGHT_PRIMARY | METASLAB_WEIGHT_SECONDARY | \ 81 METASLAB_WEIGHT_CLAIM) 82 83 /* 84 * The metaslab weight is used to encode the amount of free space in a 85 * metaslab, such that the "best" metaslab appears first when sorting the 86 * metaslabs by weight. The weight (and therefore the "best" metaslab) can 87 * be determined in two different ways: by computing a weighted sum of all 88 * the free space in the metaslab (a space based weight) or by counting only 89 * the free segments of the largest size (a segment based weight). We prefer 90 * the segment based weight because it reflects how the free space is 91 * comprised, but we cannot always use it -- legacy pools do not have the 92 * space map histogram information necessary to determine the largest 93 * contiguous regions. Pools that have the space map histogram determine 94 * the segment weight by looking at each bucket in the histogram and 95 * determining the free space whose size in bytes is in the range: 96 * [2^i, 2^(i+1)) 97 * We then encode the largest index, i, that contains regions into the 98 * segment-weighted value. 99 * 100 * Space-based weight: 101 * 102 * 64 56 48 40 32 24 16 8 0 103 * +-------+-------+-------+-------+-------+-------+-------+-------+ 104 * |PSC1| weighted-free space | 105 * +-------+-------+-------+-------+-------+-------+-------+-------+ 106 * 107 * PS - indicates primary and secondary activation 108 * C - indicates activation for claimed block zio 109 * space - the fragmentation-weighted space 110 * 111 * Segment-based weight: 112 * 113 * 64 56 48 40 32 24 16 8 0 114 * +-------+-------+-------+-------+-------+-------+-------+-------+ 115 * |PSC0| idx| count of segments in region | 116 * +-------+-------+-------+-------+-------+-------+-------+-------+ 117 * 118 * PS - indicates primary and secondary activation 119 * C - indicates activation for claimed block zio 120 * idx - index for the highest bucket in the histogram 121 * count - number of segments in the specified bucket 122 */ 123 #define WEIGHT_GET_ACTIVE(weight) BF64_GET((weight), 61, 3) 124 #define WEIGHT_SET_ACTIVE(weight, x) BF64_SET((weight), 61, 3, x) 125 126 #define WEIGHT_IS_SPACEBASED(weight) \ 127 ((weight) == 0 || BF64_GET((weight), 60, 1)) 128 #define WEIGHT_SET_SPACEBASED(weight) BF64_SET((weight), 60, 1, 1) 129 130 /* 131 * These macros are only applicable to segment-based weighting. 132 */ 133 #define WEIGHT_GET_INDEX(weight) BF64_GET((weight), 54, 6) 134 #define WEIGHT_SET_INDEX(weight, x) BF64_SET((weight), 54, 6, x) 135 #define WEIGHT_GET_COUNT(weight) BF64_GET((weight), 0, 54) 136 #define WEIGHT_SET_COUNT(weight, x) BF64_SET((weight), 0, 54, x) 137 138 /* 139 * A metaslab class encompasses a category of allocatable top-level vdevs. 140 * Each top-level vdev is associated with a metaslab group which defines 141 * the allocatable region for that vdev. Examples of these categories include 142 * "normal" for data block allocations (i.e. main pool allocations) or "log" 143 * for allocations designated for intent log devices (i.e. slog devices). 144 * When a block allocation is requested from the SPA it is associated with a 145 * metaslab_class_t, and only top-level vdevs (i.e. metaslab groups) belonging 146 * to the class can be used to satisfy that request. Allocations are done 147 * by traversing the metaslab groups that are linked off of the mc_rotor field. 148 * This rotor points to the next metaslab group where allocations will be 149 * attempted. Allocating a block is a 3 step process -- select the metaslab 150 * group, select the metaslab, and then allocate the block. The metaslab 151 * class defines the low-level block allocator that will be used as the 152 * final step in allocation. These allocators are pluggable allowing each class 153 * to use a block allocator that best suits that class. 154 */ 155 struct metaslab_class { 156 kmutex_t mc_lock; 157 spa_t *mc_spa; 158 metaslab_group_t *mc_rotor; 159 metaslab_ops_t *mc_ops; 160 uint64_t mc_aliquot; 161 162 /* 163 * Track the number of metaslab groups that have been initialized 164 * and can accept allocations. An initialized metaslab group is 165 * one has been completely added to the config (i.e. we have 166 * updated the MOS config and the space has been added to the pool). 167 */ 168 uint64_t mc_groups; 169 170 /* 171 * Toggle to enable/disable the allocation throttle. 172 */ 173 boolean_t mc_alloc_throttle_enabled; 174 175 /* 176 * The allocation throttle works on a reservation system. Whenever 177 * an asynchronous zio wants to perform an allocation it must 178 * first reserve the number of blocks that it wants to allocate. 179 * If there aren't sufficient slots available for the pending zio 180 * then that I/O is throttled until more slots free up. The current 181 * number of reserved allocations is maintained by the mc_alloc_slots 182 * refcount. The mc_alloc_max_slots value determines the maximum 183 * number of allocations that the system allows. Gang blocks are 184 * allowed to reserve slots even if we've reached the maximum 185 * number of allocations allowed. 186 */ 187 uint64_t *mc_alloc_max_slots; 188 refcount_t *mc_alloc_slots; 189 190 uint64_t mc_alloc_groups; /* # of allocatable groups */ 191 192 uint64_t mc_alloc; /* total allocated space */ 193 uint64_t mc_deferred; /* total deferred frees */ 194 uint64_t mc_space; /* total space (alloc + free) */ 195 uint64_t mc_dspace; /* total deflated space */ 196 uint64_t mc_histogram[RANGE_TREE_HISTOGRAM_SIZE]; 197 }; 198 199 /* 200 * Metaslab groups encapsulate all the allocatable regions (i.e. metaslabs) 201 * of a top-level vdev. They are linked togther to form a circular linked 202 * list and can belong to only one metaslab class. Metaslab groups may become 203 * ineligible for allocations for a number of reasons such as limited free 204 * space, fragmentation, or going offline. When this happens the allocator will 205 * simply find the next metaslab group in the linked list and attempt 206 * to allocate from that group instead. 207 */ 208 struct metaslab_group { 209 kmutex_t mg_lock; 210 metaslab_t **mg_primaries; 211 metaslab_t **mg_secondaries; 212 avl_tree_t mg_metaslab_tree; 213 uint64_t mg_aliquot; 214 boolean_t mg_allocatable; /* can we allocate? */ 215 uint64_t mg_ms_ready; 216 217 /* 218 * A metaslab group is considered to be initialized only after 219 * we have updated the MOS config and added the space to the pool. 220 * We only allow allocation attempts to a metaslab group if it 221 * has been initialized. 222 */ 223 boolean_t mg_initialized; 224 225 uint64_t mg_free_capacity; /* percentage free */ 226 int64_t mg_bias; 227 int64_t mg_activation_count; 228 metaslab_class_t *mg_class; 229 vdev_t *mg_vd; 230 taskq_t *mg_taskq; 231 metaslab_group_t *mg_prev; 232 metaslab_group_t *mg_next; 233 234 /* 235 * In order for the allocation throttle to function properly, we cannot 236 * have too many IOs going to each disk by default; the throttle 237 * operates by allocating more work to disks that finish quickly, so 238 * allocating larger chunks to each disk reduces its effectiveness. 239 * However, if the number of IOs going to each allocator is too small, 240 * we will not perform proper aggregation at the vdev_queue layer, 241 * also resulting in decreased performance. Therefore, we will use a 242 * ramp-up strategy. 243 * 244 * Each allocator in each metaslab group has a current queue depth 245 * (mg_alloc_queue_depth[allocator]) and a current max queue depth 246 * (mg_cur_max_alloc_queue_depth[allocator]), and each metaslab group 247 * has an absolute max queue depth (mg_max_alloc_queue_depth). We 248 * add IOs to an allocator until the mg_alloc_queue_depth for that 249 * allocator hits the cur_max. Every time an IO completes for a given 250 * allocator on a given metaslab group, we increment its cur_max until 251 * it reaches mg_max_alloc_queue_depth. The cur_max resets every txg to 252 * help protect against disks that decrease in performance over time. 253 * 254 * It's possible for an allocator to handle more allocations than 255 * its max. This can occur when gang blocks are required or when other 256 * groups are unable to handle their share of allocations. 257 */ 258 uint64_t mg_max_alloc_queue_depth; 259 uint64_t *mg_cur_max_alloc_queue_depth; 260 refcount_t *mg_alloc_queue_depth; 261 int mg_allocators; 262 /* 263 * A metalab group that can no longer allocate the minimum block 264 * size will set mg_no_free_space. Once a metaslab group is out 265 * of space then its share of work must be distributed to other 266 * groups. 267 */ 268 boolean_t mg_no_free_space; 269 270 uint64_t mg_allocations; 271 uint64_t mg_failed_allocations; 272 uint64_t mg_fragmentation; 273 uint64_t mg_histogram[RANGE_TREE_HISTOGRAM_SIZE]; 274 275 int mg_ms_initializing; 276 boolean_t mg_initialize_updating; 277 kmutex_t mg_ms_initialize_lock; 278 kcondvar_t mg_ms_initialize_cv; 279 }; 280 281 /* 282 * This value defines the number of elements in the ms_lbas array. The value 283 * of 64 was chosen as it covers all power of 2 buckets up to UINT64_MAX. 284 * This is the equivalent of highbit(UINT64_MAX). 285 */ 286 #define MAX_LBAS 64 287 288 /* 289 * Each metaslab maintains a set of in-core trees to track metaslab 290 * operations. The in-core free tree (ms_allocatable) contains the list of 291 * free segments which are eligible for allocation. As blocks are 292 * allocated, the allocated segment are removed from the ms_allocatable and 293 * added to a per txg allocation tree (ms_allocating). As blocks are 294 * freed, they are added to the free tree (ms_freeing). These trees 295 * allow us to process all allocations and frees in syncing context 296 * where it is safe to update the on-disk space maps. An additional set 297 * of in-core trees is maintained to track deferred frees 298 * (ms_defer). Once a block is freed it will move from the 299 * ms_freed to the ms_defer tree. A deferred free means that a block 300 * has been freed but cannot be used by the pool until TXG_DEFER_SIZE 301 * transactions groups later. For example, a block that is freed in txg 302 * 50 will not be available for reallocation until txg 52 (50 + 303 * TXG_DEFER_SIZE). This provides a safety net for uberblock rollback. 304 * A pool could be safely rolled back TXG_DEFERS_SIZE transactions 305 * groups and ensure that no block has been reallocated. 306 * 307 * The simplified transition diagram looks like this: 308 * 309 * 310 * ALLOCATE 311 * | 312 * V 313 * free segment (ms_allocatable) -> ms_allocating[4] -> (write to space map) 314 * ^ 315 * | ms_freeing <--- FREE 316 * | | 317 * | v 318 * | ms_freed 319 * | | 320 * +-------- ms_defer[2] <-------+-------> (write to space map) 321 * 322 * 323 * Each metaslab's space is tracked in a single space map in the MOS, 324 * which is only updated in syncing context. Each time we sync a txg, 325 * we append the allocs and frees from that txg to the space map. The 326 * pool space is only updated once all metaslabs have finished syncing. 327 * 328 * To load the in-core free tree we read the space map from disk. This 329 * object contains a series of alloc and free records that are combined 330 * to make up the list of all free segments in this metaslab. These 331 * segments are represented in-core by the ms_allocatable and are stored 332 * in an AVL tree. 333 * 334 * As the space map grows (as a result of the appends) it will 335 * eventually become space-inefficient. When the metaslab's in-core 336 * free tree is zfs_condense_pct/100 times the size of the minimal 337 * on-disk representation, we rewrite it in its minimized form. If a 338 * metaslab needs to condense then we must set the ms_condensing flag to 339 * ensure that allocations are not performed on the metaslab that is 340 * being written. 341 */ 342 struct metaslab { 343 kmutex_t ms_lock; 344 kmutex_t ms_sync_lock; 345 kcondvar_t ms_load_cv; 346 space_map_t *ms_sm; 347 uint64_t ms_id; 348 uint64_t ms_start; 349 uint64_t ms_size; 350 uint64_t ms_fragmentation; 351 352 range_tree_t *ms_allocating[TXG_SIZE]; 353 range_tree_t *ms_allocatable; 354 355 /* 356 * The following range trees are accessed only from syncing context. 357 * ms_free*tree only have entries while syncing, and are empty 358 * between syncs. 359 */ 360 range_tree_t *ms_freeing; /* to free this syncing txg */ 361 range_tree_t *ms_freed; /* already freed this syncing txg */ 362 range_tree_t *ms_defer[TXG_DEFER_SIZE]; 363 range_tree_t *ms_checkpointing; /* to add to the checkpoint */ 364 365 boolean_t ms_condensing; /* condensing? */ 366 boolean_t ms_condense_wanted; 367 uint64_t ms_condense_checked_txg; 368 369 uint64_t ms_initializing; /* leaves initializing this ms */ 370 371 /* 372 * We must hold both ms_lock and ms_group->mg_lock in order to 373 * modify ms_loaded. 374 */ 375 boolean_t ms_loaded; 376 boolean_t ms_loading; 377 378 int64_t ms_deferspace; /* sum of ms_defermap[] space */ 379 uint64_t ms_weight; /* weight vs. others in group */ 380 uint64_t ms_activation_weight; /* activation weight */ 381 382 /* 383 * Track of whenever a metaslab is selected for loading or allocation. 384 * We use this value to determine how long the metaslab should 385 * stay cached. 386 */ 387 uint64_t ms_selected_txg; 388 389 uint64_t ms_alloc_txg; /* last successful alloc (debug only) */ 390 uint64_t ms_max_size; /* maximum allocatable size */ 391 392 /* 393 * -1 if it's not active in an allocator, otherwise set to the allocator 394 * this metaslab is active for. 395 */ 396 int ms_allocator; 397 boolean_t ms_primary; /* Only valid if ms_allocator is not -1 */ 398 399 /* 400 * The metaslab block allocators can optionally use a size-ordered 401 * range tree and/or an array of LBAs. Not all allocators use 402 * this functionality. The ms_allocatable_by_size should always 403 * contain the same number of segments as the ms_allocatable. The 404 * only difference is that the ms_allocatable_by_size is ordered by 405 * segment sizes. 406 */ 407 avl_tree_t ms_allocatable_by_size; 408 uint64_t ms_lbas[MAX_LBAS]; 409 410 metaslab_group_t *ms_group; /* metaslab group */ 411 avl_node_t ms_group_node; /* node in metaslab group tree */ 412 txg_node_t ms_txg_node; /* per-txg dirty metaslab links */ 413 414 boolean_t ms_new; 415 }; 416 417 #ifdef __cplusplus 418 } 419 #endif 420 421 #endif /* _SYS_METASLAB_IMPL_H */ 422