metaslab_impl.h revision 339111
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 41extern "C" { 42#endif 43 44/* 45 * Metaslab allocation tracing record. 46 */ 47typedef 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 */ 63typedef 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 */ 155struct 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_minblocksize; 197 uint64_t mc_histogram[RANGE_TREE_HISTOGRAM_SIZE]; 198}; 199 200/* 201 * Metaslab groups encapsulate all the allocatable regions (i.e. metaslabs) 202 * of a top-level vdev. They are linked togther to form a circular linked 203 * list and can belong to only one metaslab class. Metaslab groups may become 204 * ineligible for allocations for a number of reasons such as limited free 205 * space, fragmentation, or going offline. When this happens the allocator will 206 * simply find the next metaslab group in the linked list and attempt 207 * to allocate from that group instead. 208 */ 209struct metaslab_group { 210 kmutex_t mg_lock; 211 metaslab_t **mg_primaries; 212 metaslab_t **mg_secondaries; 213 avl_tree_t mg_metaslab_tree; 214 uint64_t mg_aliquot; 215 boolean_t mg_allocatable; /* can we allocate? */ 216 uint64_t mg_ms_ready; 217 218 /* 219 * A metaslab group is considered to be initialized only after 220 * we have updated the MOS config and added the space to the pool. 221 * We only allow allocation attempts to a metaslab group if it 222 * has been initialized. 223 */ 224 boolean_t mg_initialized; 225 226 uint64_t mg_free_capacity; /* percentage free */ 227 int64_t mg_bias; 228 int64_t mg_activation_count; 229 metaslab_class_t *mg_class; 230 vdev_t *mg_vd; 231 taskq_t *mg_taskq; 232 metaslab_group_t *mg_prev; 233 metaslab_group_t *mg_next; 234 235 /* 236 * In order for the allocation throttle to function properly, we cannot 237 * have too many IOs going to each disk by default; the throttle 238 * operates by allocating more work to disks that finish quickly, so 239 * allocating larger chunks to each disk reduces its effectiveness. 240 * However, if the number of IOs going to each allocator is too small, 241 * we will not perform proper aggregation at the vdev_queue layer, 242 * also resulting in decreased performance. Therefore, we will use a 243 * ramp-up strategy. 244 * 245 * Each allocator in each metaslab group has a current queue depth 246 * (mg_alloc_queue_depth[allocator]) and a current max queue depth 247 * (mg_cur_max_alloc_queue_depth[allocator]), and each metaslab group 248 * has an absolute max queue depth (mg_max_alloc_queue_depth). We 249 * add IOs to an allocator until the mg_alloc_queue_depth for that 250 * allocator hits the cur_max. Every time an IO completes for a given 251 * allocator on a given metaslab group, we increment its cur_max until 252 * it reaches mg_max_alloc_queue_depth. The cur_max resets every txg to 253 * help protect against disks that decrease in performance over time. 254 * 255 * It's possible for an allocator to handle more allocations than 256 * its max. This can occur when gang blocks are required or when other 257 * groups are unable to handle their share of allocations. 258 */ 259 uint64_t mg_max_alloc_queue_depth; 260 uint64_t *mg_cur_max_alloc_queue_depth; 261 refcount_t *mg_alloc_queue_depth; 262 int mg_allocators; 263 /* 264 * A metalab group that can no longer allocate the minimum block 265 * size will set mg_no_free_space. Once a metaslab group is out 266 * of space then its share of work must be distributed to other 267 * groups. 268 */ 269 boolean_t mg_no_free_space; 270 271 uint64_t mg_allocations; 272 uint64_t mg_failed_allocations; 273 uint64_t mg_fragmentation; 274 uint64_t mg_histogram[RANGE_TREE_HISTOGRAM_SIZE]; 275 276 int mg_ms_initializing; 277 boolean_t mg_initialize_updating; 278 kmutex_t mg_ms_initialize_lock; 279 kcondvar_t mg_ms_initialize_cv; 280}; 281 282/* 283 * This value defines the number of elements in the ms_lbas array. The value 284 * of 64 was chosen as it covers all power of 2 buckets up to UINT64_MAX. 285 * This is the equivalent of highbit(UINT64_MAX). 286 */ 287#define MAX_LBAS 64 288 289/* 290 * Each metaslab maintains a set of in-core trees to track metaslab 291 * operations. The in-core free tree (ms_allocatable) contains the list of 292 * free segments which are eligible for allocation. As blocks are 293 * allocated, the allocated segment are removed from the ms_allocatable and 294 * added to a per txg allocation tree (ms_allocating). As blocks are 295 * freed, they are added to the free tree (ms_freeing). These trees 296 * allow us to process all allocations and frees in syncing context 297 * where it is safe to update the on-disk space maps. An additional set 298 * of in-core trees is maintained to track deferred frees 299 * (ms_defer). Once a block is freed it will move from the 300 * ms_freed to the ms_defer tree. A deferred free means that a block 301 * has been freed but cannot be used by the pool until TXG_DEFER_SIZE 302 * transactions groups later. For example, a block that is freed in txg 303 * 50 will not be available for reallocation until txg 52 (50 + 304 * TXG_DEFER_SIZE). This provides a safety net for uberblock rollback. 305 * A pool could be safely rolled back TXG_DEFERS_SIZE transactions 306 * groups and ensure that no block has been reallocated. 307 * 308 * The simplified transition diagram looks like this: 309 * 310 * 311 * ALLOCATE 312 * | 313 * V 314 * free segment (ms_allocatable) -> ms_allocating[4] -> (write to space map) 315 * ^ 316 * | ms_freeing <--- FREE 317 * | | 318 * | v 319 * | ms_freed 320 * | | 321 * +-------- ms_defer[2] <-------+-------> (write to space map) 322 * 323 * 324 * Each metaslab's space is tracked in a single space map in the MOS, 325 * which is only updated in syncing context. Each time we sync a txg, 326 * we append the allocs and frees from that txg to the space map. The 327 * pool space is only updated once all metaslabs have finished syncing. 328 * 329 * To load the in-core free tree we read the space map from disk. This 330 * object contains a series of alloc and free records that are combined 331 * to make up the list of all free segments in this metaslab. These 332 * segments are represented in-core by the ms_allocatable and are stored 333 * in an AVL tree. 334 * 335 * As the space map grows (as a result of the appends) it will 336 * eventually become space-inefficient. When the metaslab's in-core 337 * free tree is zfs_condense_pct/100 times the size of the minimal 338 * on-disk representation, we rewrite it in its minimized form. If a 339 * metaslab needs to condense then we must set the ms_condensing flag to 340 * ensure that allocations are not performed on the metaslab that is 341 * being written. 342 */ 343struct metaslab { 344 kmutex_t ms_lock; 345 kmutex_t ms_sync_lock; 346 kcondvar_t ms_load_cv; 347 space_map_t *ms_sm; 348 uint64_t ms_id; 349 uint64_t ms_start; 350 uint64_t ms_size; 351 uint64_t ms_fragmentation; 352 353 range_tree_t *ms_allocating[TXG_SIZE]; 354 range_tree_t *ms_allocatable; 355 356 /* 357 * The following range trees are accessed only from syncing context. 358 * ms_free*tree only have entries while syncing, and are empty 359 * between syncs. 360 */ 361 range_tree_t *ms_freeing; /* to free this syncing txg */ 362 range_tree_t *ms_freed; /* already freed this syncing txg */ 363 range_tree_t *ms_defer[TXG_DEFER_SIZE]; 364 range_tree_t *ms_checkpointing; /* to add to the checkpoint */ 365 366 boolean_t ms_condensing; /* condensing? */ 367 boolean_t ms_condense_wanted; 368 uint64_t ms_condense_checked_txg; 369 370 uint64_t ms_initializing; /* leaves initializing this ms */ 371 372 /* 373 * We must hold both ms_lock and ms_group->mg_lock in order to 374 * modify ms_loaded. 375 */ 376 boolean_t ms_loaded; 377 boolean_t ms_loading; 378 379 int64_t ms_deferspace; /* sum of ms_defermap[] space */ 380 uint64_t ms_weight; /* weight vs. others in group */ 381 uint64_t ms_activation_weight; /* activation weight */ 382 383 /* 384 * Track of whenever a metaslab is selected for loading or allocation. 385 * We use this value to determine how long the metaslab should 386 * stay cached. 387 */ 388 uint64_t ms_selected_txg; 389 390 uint64_t ms_alloc_txg; /* last successful alloc (debug only) */ 391 uint64_t ms_max_size; /* maximum allocatable size */ 392 393 /* 394 * -1 if it's not active in an allocator, otherwise set to the allocator 395 * this metaslab is active for. 396 */ 397 int ms_allocator; 398 boolean_t ms_primary; /* Only valid if ms_allocator is not -1 */ 399 400 /* 401 * The metaslab block allocators can optionally use a size-ordered 402 * range tree and/or an array of LBAs. Not all allocators use 403 * this functionality. The ms_allocatable_by_size should always 404 * contain the same number of segments as the ms_allocatable. The 405 * only difference is that the ms_allocatable_by_size is ordered by 406 * segment sizes. 407 */ 408 avl_tree_t ms_allocatable_by_size; 409 uint64_t ms_lbas[MAX_LBAS]; 410 411 metaslab_group_t *ms_group; /* metaslab group */ 412 avl_node_t ms_group_node; /* node in metaslab group tree */ 413 txg_node_t ms_txg_node; /* per-txg dirty metaslab links */ 414 415 boolean_t ms_new; 416}; 417 418#ifdef __cplusplus 419} 420#endif 421 422#endif /* _SYS_METASLAB_IMPL_H */ 423