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 segment are removed from the ms_tree and
261 * added to a per txg allocation tree (ms_alloctree). As blocks are
262 * freed, they are added to the free tree (ms_freeingtree). These trees
263 * allow us to process all allocations and frees in syncing context
264 * where it is safe to update the on-disk space maps. An additional set
265 * of in-core trees is maintained to track deferred frees
266 * (ms_defertree). Once a block is freed it will move from the
267 * ms_freedtree to the ms_defertree. A deferred free means that a block
268 * has been freed but cannot be used by the pool until TXG_DEFER_SIZE
269 * transactions groups later. For example, a block that is freed in txg
270 * 50 will not be available for reallocation until txg 52 (50 +
271 * TXG_DEFER_SIZE). This provides a safety net for uberblock rollback.
272 * A pool could be safely rolled back TXG_DEFERS_SIZE transactions
273 * groups and ensure that no block has been reallocated.
274 *
275 * The simplified transition diagram looks like this:
276 *
277 *
278 * ALLOCATE
279 * |
280 * V
281 * free segment (ms_tree) -----> ms_alloctree[4] ----> (write to space map)
282 * ^
283 * | ms_freeingtree <--- FREE
284 * | |
285 * | v
286 * | ms_freedtree
287 * | |
288 * +-------- ms_defertree[2] <-------+---------> (write to space map)
289 *
290 *
291 * Each metaslab's space is tracked in a single space map in the MOS,
292 * which is only updated in syncing context. Each time we sync a txg,
293 * we append the allocs and frees from that txg to the space map. The
294 * pool space is only updated once all metaslabs have finished syncing.
295 *
296 * To load the in-core free tree we read the space map from disk. This
297 * object contains a series of alloc and free records that are combined
298 * to make up the list of all free segments in this metaslab. These
299 * segments are represented in-core by the ms_tree and are stored in an
300 * AVL tree.
301 *
302 * As the space map grows (as a result of the appends) it will
303 * eventually become space-inefficient. When the metaslab's in-core
304 * free tree is zfs_condense_pct/100 times the size of the minimal
305 * on-disk representation, we rewrite it in its minimized form. If a
306 * metaslab needs to condense then we must set the ms_condensing flag to
307 * ensure that allocations are not performed on the metaslab that is
308 * being written.
309 */
310 struct metaslab {
311 kmutex_t ms_lock;
312 kmutex_t ms_sync_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 */