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.
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.
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]
22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23 * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
24 * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
27 #include <sys/zfs_context.h>
29 #include <sys/dmu_tx.h>
30 #include <sys/space_map.h>
31 #include <sys/metaslab_impl.h>
32 #include <sys/vdev_impl.h>
34 #include <sys/spa_impl.h>
35 #include <sys/zfeature.h>
37 #define WITH_DF_BLOCK_ALLOCATOR
39 #define GANG_ALLOCATION(flags) \
40 ((flags) & (METASLAB_GANG_CHILD | METASLAB_GANG_HEADER))
42 #define METASLAB_WEIGHT_PRIMARY (1ULL << 63)
43 #define METASLAB_WEIGHT_SECONDARY (1ULL << 62)
44 #define METASLAB_ACTIVE_MASK \
45 (METASLAB_WEIGHT_PRIMARY | METASLAB_WEIGHT_SECONDARY)
48 * Metaslab granularity, in bytes. This is roughly similar to what would be
49 * referred to as the "stripe size" in traditional RAID arrays. In normal
50 * operation, we will try to write this amount of data to a top-level vdev
51 * before moving on to the next one.
53 unsigned long metaslab_aliquot = 512 << 10;
55 uint64_t metaslab_gang_bang = SPA_MAXBLOCKSIZE + 1; /* force gang blocks */
58 * The in-core space map representation is more compact than its on-disk form.
59 * The zfs_condense_pct determines how much more compact the in-core
60 * space_map representation must be before we compact it on-disk.
61 * Values should be greater than or equal to 100.
63 int zfs_condense_pct = 200;
66 * Condensing a metaslab is not guaranteed to actually reduce the amount of
67 * space used on disk. In particular, a space map uses data in increments of
68 * MAX(1 << ashift, space_map_blksz), so a metaslab might use the
69 * same number of blocks after condensing. Since the goal of condensing is to
70 * reduce the number of IOPs required to read the space map, we only want to
71 * condense when we can be sure we will reduce the number of blocks used by the
72 * space map. Unfortunately, we cannot precisely compute whether or not this is
73 * the case in metaslab_should_condense since we are holding ms_lock. Instead,
74 * we apply the following heuristic: do not condense a spacemap unless the
75 * uncondensed size consumes greater than zfs_metaslab_condense_block_threshold
78 int zfs_metaslab_condense_block_threshold = 4;
81 * The zfs_mg_noalloc_threshold defines which metaslab groups should
82 * be eligible for allocation. The value is defined as a percentage of
83 * free space. Metaslab groups that have more free space than
84 * zfs_mg_noalloc_threshold are always eligible for allocations. Once
85 * a metaslab group's free space is less than or equal to the
86 * zfs_mg_noalloc_threshold the allocator will avoid allocating to that
87 * group unless all groups in the pool have reached zfs_mg_noalloc_threshold.
88 * Once all groups in the pool reach zfs_mg_noalloc_threshold then all
89 * groups are allowed to accept allocations. Gang blocks are always
90 * eligible to allocate on any metaslab group. The default value of 0 means
91 * no metaslab group will be excluded based on this criterion.
93 int zfs_mg_noalloc_threshold = 0;
96 * Metaslab groups are considered eligible for allocations if their
97 * fragmenation metric (measured as a percentage) is less than or equal to
98 * zfs_mg_fragmentation_threshold. If a metaslab group exceeds this threshold
99 * then it will be skipped unless all metaslab groups within the metaslab
100 * class have also crossed this threshold.
102 int zfs_mg_fragmentation_threshold = 85;
105 * Allow metaslabs to keep their active state as long as their fragmentation
106 * percentage is less than or equal to zfs_metaslab_fragmentation_threshold. An
107 * active metaslab that exceeds this threshold will no longer keep its active
108 * status allowing better metaslabs to be selected.
110 int zfs_metaslab_fragmentation_threshold = 70;
113 * When set will load all metaslabs when pool is first opened.
115 int metaslab_debug_load = 0;
118 * When set will prevent metaslabs from being unloaded.
120 int metaslab_debug_unload = 0;
123 * Minimum size which forces the dynamic allocator to change
124 * it's allocation strategy. Once the space map cannot satisfy
125 * an allocation of this size then it switches to using more
126 * aggressive strategy (i.e search by size rather than offset).
128 uint64_t metaslab_df_alloc_threshold = SPA_MAXBLOCKSIZE;
131 * The minimum free space, in percent, which must be available
132 * in a space map to continue allocations in a first-fit fashion.
133 * Once the space_map's free space drops below this level we dynamically
134 * switch to using best-fit allocations.
136 int metaslab_df_free_pct = 4;
139 * Percentage of all cpus that can be used by the metaslab taskq.
141 int metaslab_load_pct = 50;
144 * Determines how many txgs a metaslab may remain loaded without having any
145 * allocations from it. As long as a metaslab continues to be used we will
148 int metaslab_unload_delay = TXG_SIZE * 2;
151 * Max number of metaslabs per group to preload.
153 int metaslab_preload_limit = SPA_DVAS_PER_BP;
156 * Enable/disable preloading of metaslab.
158 int metaslab_preload_enabled = B_TRUE;
161 * Enable/disable fragmentation weighting on metaslabs.
163 int metaslab_fragmentation_factor_enabled = B_TRUE;
166 * Enable/disable lba weighting (i.e. outer tracks are given preference).
168 int metaslab_lba_weighting_enabled = B_TRUE;
171 * Enable/disable metaslab group biasing.
173 int metaslab_bias_enabled = B_TRUE;
175 static uint64_t metaslab_fragmentation(metaslab_t *);
178 * ==========================================================================
180 * ==========================================================================
183 metaslab_class_create(spa_t *spa, metaslab_ops_t *ops)
185 metaslab_class_t *mc;
187 mc = kmem_zalloc(sizeof (metaslab_class_t), KM_SLEEP);
192 mutex_init(&mc->mc_lock, NULL, MUTEX_DEFAULT, NULL);
193 refcount_create_tracked(&mc->mc_alloc_slots);
199 metaslab_class_destroy(metaslab_class_t *mc)
201 ASSERT(mc->mc_rotor == NULL);
202 ASSERT(mc->mc_alloc == 0);
203 ASSERT(mc->mc_deferred == 0);
204 ASSERT(mc->mc_space == 0);
205 ASSERT(mc->mc_dspace == 0);
207 refcount_destroy(&mc->mc_alloc_slots);
208 mutex_destroy(&mc->mc_lock);
209 kmem_free(mc, sizeof (metaslab_class_t));
213 metaslab_class_validate(metaslab_class_t *mc)
215 metaslab_group_t *mg;
219 * Must hold one of the spa_config locks.
221 ASSERT(spa_config_held(mc->mc_spa, SCL_ALL, RW_READER) ||
222 spa_config_held(mc->mc_spa, SCL_ALL, RW_WRITER));
224 if ((mg = mc->mc_rotor) == NULL)
229 ASSERT(vd->vdev_mg != NULL);
230 ASSERT3P(vd->vdev_top, ==, vd);
231 ASSERT3P(mg->mg_class, ==, mc);
232 ASSERT3P(vd->vdev_ops, !=, &vdev_hole_ops);
233 } while ((mg = mg->mg_next) != mc->mc_rotor);
239 metaslab_class_space_update(metaslab_class_t *mc, int64_t alloc_delta,
240 int64_t defer_delta, int64_t space_delta, int64_t dspace_delta)
242 atomic_add_64(&mc->mc_alloc, alloc_delta);
243 atomic_add_64(&mc->mc_deferred, defer_delta);
244 atomic_add_64(&mc->mc_space, space_delta);
245 atomic_add_64(&mc->mc_dspace, dspace_delta);
249 metaslab_class_get_alloc(metaslab_class_t *mc)
251 return (mc->mc_alloc);
255 metaslab_class_get_deferred(metaslab_class_t *mc)
257 return (mc->mc_deferred);
261 metaslab_class_get_space(metaslab_class_t *mc)
263 return (mc->mc_space);
267 metaslab_class_get_dspace(metaslab_class_t *mc)
269 return (spa_deflate(mc->mc_spa) ? mc->mc_dspace : mc->mc_space);
273 metaslab_class_histogram_verify(metaslab_class_t *mc)
275 vdev_t *rvd = mc->mc_spa->spa_root_vdev;
279 if ((zfs_flags & ZFS_DEBUG_HISTOGRAM_VERIFY) == 0)
282 mc_hist = kmem_zalloc(sizeof (uint64_t) * RANGE_TREE_HISTOGRAM_SIZE,
285 for (c = 0; c < rvd->vdev_children; c++) {
286 vdev_t *tvd = rvd->vdev_child[c];
287 metaslab_group_t *mg = tvd->vdev_mg;
290 * Skip any holes, uninitialized top-levels, or
291 * vdevs that are not in this metalab class.
293 if (tvd->vdev_ishole || tvd->vdev_ms_shift == 0 ||
294 mg->mg_class != mc) {
298 for (i = 0; i < RANGE_TREE_HISTOGRAM_SIZE; i++)
299 mc_hist[i] += mg->mg_histogram[i];
302 for (i = 0; i < RANGE_TREE_HISTOGRAM_SIZE; i++)
303 VERIFY3U(mc_hist[i], ==, mc->mc_histogram[i]);
305 kmem_free(mc_hist, sizeof (uint64_t) * RANGE_TREE_HISTOGRAM_SIZE);
309 * Calculate the metaslab class's fragmentation metric. The metric
310 * is weighted based on the space contribution of each metaslab group.
311 * The return value will be a number between 0 and 100 (inclusive), or
312 * ZFS_FRAG_INVALID if the metric has not been set. See comment above the
313 * zfs_frag_table for more information about the metric.
316 metaslab_class_fragmentation(metaslab_class_t *mc)
318 vdev_t *rvd = mc->mc_spa->spa_root_vdev;
319 uint64_t fragmentation = 0;
322 spa_config_enter(mc->mc_spa, SCL_VDEV, FTAG, RW_READER);
324 for (c = 0; c < rvd->vdev_children; c++) {
325 vdev_t *tvd = rvd->vdev_child[c];
326 metaslab_group_t *mg = tvd->vdev_mg;
329 * Skip any holes, uninitialized top-levels, or
330 * vdevs that are not in this metalab class.
332 if (tvd->vdev_ishole || tvd->vdev_ms_shift == 0 ||
333 mg->mg_class != mc) {
338 * If a metaslab group does not contain a fragmentation
339 * metric then just bail out.
341 if (mg->mg_fragmentation == ZFS_FRAG_INVALID) {
342 spa_config_exit(mc->mc_spa, SCL_VDEV, FTAG);
343 return (ZFS_FRAG_INVALID);
347 * Determine how much this metaslab_group is contributing
348 * to the overall pool fragmentation metric.
350 fragmentation += mg->mg_fragmentation *
351 metaslab_group_get_space(mg);
353 fragmentation /= metaslab_class_get_space(mc);
355 ASSERT3U(fragmentation, <=, 100);
356 spa_config_exit(mc->mc_spa, SCL_VDEV, FTAG);
357 return (fragmentation);
361 * Calculate the amount of expandable space that is available in
362 * this metaslab class. If a device is expanded then its expandable
363 * space will be the amount of allocatable space that is currently not
364 * part of this metaslab class.
367 metaslab_class_expandable_space(metaslab_class_t *mc)
369 vdev_t *rvd = mc->mc_spa->spa_root_vdev;
373 spa_config_enter(mc->mc_spa, SCL_VDEV, FTAG, RW_READER);
374 for (c = 0; c < rvd->vdev_children; c++) {
375 vdev_t *tvd = rvd->vdev_child[c];
376 metaslab_group_t *mg = tvd->vdev_mg;
378 if (tvd->vdev_ishole || tvd->vdev_ms_shift == 0 ||
379 mg->mg_class != mc) {
383 space += tvd->vdev_max_asize - tvd->vdev_asize;
385 spa_config_exit(mc->mc_spa, SCL_VDEV, FTAG);
390 * ==========================================================================
392 * ==========================================================================
395 metaslab_compare(const void *x1, const void *x2)
397 const metaslab_t *m1 = (const metaslab_t *)x1;
398 const metaslab_t *m2 = (const metaslab_t *)x2;
400 int cmp = AVL_CMP(m2->ms_weight, m1->ms_weight);
404 IMPLY(AVL_CMP(m1->ms_start, m2->ms_start) == 0, m1 == m2);
406 return (AVL_CMP(m1->ms_start, m2->ms_start));
410 * Update the allocatable flag and the metaslab group's capacity.
411 * The allocatable flag is set to true if the capacity is below
412 * the zfs_mg_noalloc_threshold or has a fragmentation value that is
413 * greater than zfs_mg_fragmentation_threshold. If a metaslab group
414 * transitions from allocatable to non-allocatable or vice versa then the
415 * metaslab group's class is updated to reflect the transition.
418 metaslab_group_alloc_update(metaslab_group_t *mg)
420 vdev_t *vd = mg->mg_vd;
421 metaslab_class_t *mc = mg->mg_class;
422 vdev_stat_t *vs = &vd->vdev_stat;
423 boolean_t was_allocatable;
424 boolean_t was_initialized;
426 ASSERT(vd == vd->vdev_top);
428 mutex_enter(&mg->mg_lock);
429 was_allocatable = mg->mg_allocatable;
430 was_initialized = mg->mg_initialized;
432 mg->mg_free_capacity = ((vs->vs_space - vs->vs_alloc) * 100) /
435 mutex_enter(&mc->mc_lock);
438 * If the metaslab group was just added then it won't
439 * have any space until we finish syncing out this txg.
440 * At that point we will consider it initialized and available
441 * for allocations. We also don't consider non-activated
442 * metaslab groups (e.g. vdevs that are in the middle of being removed)
443 * to be initialized, because they can't be used for allocation.
445 mg->mg_initialized = metaslab_group_initialized(mg);
446 if (!was_initialized && mg->mg_initialized) {
448 } else if (was_initialized && !mg->mg_initialized) {
449 ASSERT3U(mc->mc_groups, >, 0);
452 if (mg->mg_initialized)
453 mg->mg_no_free_space = B_FALSE;
456 * A metaslab group is considered allocatable if it has plenty
457 * of free space or is not heavily fragmented. We only take
458 * fragmentation into account if the metaslab group has a valid
459 * fragmentation metric (i.e. a value between 0 and 100).
461 mg->mg_allocatable = (mg->mg_activation_count > 0 &&
462 mg->mg_free_capacity > zfs_mg_noalloc_threshold &&
463 (mg->mg_fragmentation == ZFS_FRAG_INVALID ||
464 mg->mg_fragmentation <= zfs_mg_fragmentation_threshold));
467 * The mc_alloc_groups maintains a count of the number of
468 * groups in this metaslab class that are still above the
469 * zfs_mg_noalloc_threshold. This is used by the allocating
470 * threads to determine if they should avoid allocations to
471 * a given group. The allocator will avoid allocations to a group
472 * if that group has reached or is below the zfs_mg_noalloc_threshold
473 * and there are still other groups that are above the threshold.
474 * When a group transitions from allocatable to non-allocatable or
475 * vice versa we update the metaslab class to reflect that change.
476 * When the mc_alloc_groups value drops to 0 that means that all
477 * groups have reached the zfs_mg_noalloc_threshold making all groups
478 * eligible for allocations. This effectively means that all devices
479 * are balanced again.
481 if (was_allocatable && !mg->mg_allocatable)
482 mc->mc_alloc_groups--;
483 else if (!was_allocatable && mg->mg_allocatable)
484 mc->mc_alloc_groups++;
485 mutex_exit(&mc->mc_lock);
487 mutex_exit(&mg->mg_lock);
491 metaslab_group_create(metaslab_class_t *mc, vdev_t *vd)
493 metaslab_group_t *mg;
495 mg = kmem_zalloc(sizeof (metaslab_group_t), KM_SLEEP);
496 mutex_init(&mg->mg_lock, NULL, MUTEX_DEFAULT, NULL);
497 avl_create(&mg->mg_metaslab_tree, metaslab_compare,
498 sizeof (metaslab_t), offsetof(struct metaslab, ms_group_node));
501 mg->mg_activation_count = 0;
502 mg->mg_initialized = B_FALSE;
503 mg->mg_no_free_space = B_TRUE;
504 refcount_create_tracked(&mg->mg_alloc_queue_depth);
506 mg->mg_taskq = taskq_create("metaslab_group_taskq", metaslab_load_pct,
507 maxclsyspri, 10, INT_MAX, TASKQ_THREADS_CPU_PCT | TASKQ_DYNAMIC);
513 metaslab_group_destroy(metaslab_group_t *mg)
515 ASSERT(mg->mg_prev == NULL);
516 ASSERT(mg->mg_next == NULL);
518 * We may have gone below zero with the activation count
519 * either because we never activated in the first place or
520 * because we're done, and possibly removing the vdev.
522 ASSERT(mg->mg_activation_count <= 0);
524 taskq_destroy(mg->mg_taskq);
525 avl_destroy(&mg->mg_metaslab_tree);
526 mutex_destroy(&mg->mg_lock);
527 refcount_destroy(&mg->mg_alloc_queue_depth);
528 kmem_free(mg, sizeof (metaslab_group_t));
532 metaslab_group_activate(metaslab_group_t *mg)
534 metaslab_class_t *mc = mg->mg_class;
535 metaslab_group_t *mgprev, *mgnext;
537 ASSERT(spa_config_held(mc->mc_spa, SCL_ALLOC, RW_WRITER));
539 ASSERT(mc->mc_rotor != mg);
540 ASSERT(mg->mg_prev == NULL);
541 ASSERT(mg->mg_next == NULL);
542 ASSERT(mg->mg_activation_count <= 0);
544 if (++mg->mg_activation_count <= 0)
547 mg->mg_aliquot = metaslab_aliquot * MAX(1, mg->mg_vd->vdev_children);
548 metaslab_group_alloc_update(mg);
550 if ((mgprev = mc->mc_rotor) == NULL) {
554 mgnext = mgprev->mg_next;
555 mg->mg_prev = mgprev;
556 mg->mg_next = mgnext;
557 mgprev->mg_next = mg;
558 mgnext->mg_prev = mg;
564 metaslab_group_passivate(metaslab_group_t *mg)
566 metaslab_class_t *mc = mg->mg_class;
567 metaslab_group_t *mgprev, *mgnext;
569 ASSERT(spa_config_held(mc->mc_spa, SCL_ALLOC, RW_WRITER));
571 if (--mg->mg_activation_count != 0) {
572 ASSERT(mc->mc_rotor != mg);
573 ASSERT(mg->mg_prev == NULL);
574 ASSERT(mg->mg_next == NULL);
575 ASSERT(mg->mg_activation_count < 0);
579 taskq_wait_outstanding(mg->mg_taskq, 0);
580 metaslab_group_alloc_update(mg);
582 mgprev = mg->mg_prev;
583 mgnext = mg->mg_next;
588 mc->mc_rotor = mgnext;
589 mgprev->mg_next = mgnext;
590 mgnext->mg_prev = mgprev;
598 metaslab_group_initialized(metaslab_group_t *mg)
600 vdev_t *vd = mg->mg_vd;
601 vdev_stat_t *vs = &vd->vdev_stat;
603 return (vs->vs_space != 0 && mg->mg_activation_count > 0);
607 metaslab_group_get_space(metaslab_group_t *mg)
609 return ((1ULL << mg->mg_vd->vdev_ms_shift) * mg->mg_vd->vdev_ms_count);
613 metaslab_group_histogram_verify(metaslab_group_t *mg)
616 vdev_t *vd = mg->mg_vd;
617 uint64_t ashift = vd->vdev_ashift;
620 if ((zfs_flags & ZFS_DEBUG_HISTOGRAM_VERIFY) == 0)
623 mg_hist = kmem_zalloc(sizeof (uint64_t) * RANGE_TREE_HISTOGRAM_SIZE,
626 ASSERT3U(RANGE_TREE_HISTOGRAM_SIZE, >=,
627 SPACE_MAP_HISTOGRAM_SIZE + ashift);
629 for (m = 0; m < vd->vdev_ms_count; m++) {
630 metaslab_t *msp = vd->vdev_ms[m];
632 if (msp->ms_sm == NULL)
635 for (i = 0; i < SPACE_MAP_HISTOGRAM_SIZE; i++)
636 mg_hist[i + ashift] +=
637 msp->ms_sm->sm_phys->smp_histogram[i];
640 for (i = 0; i < RANGE_TREE_HISTOGRAM_SIZE; i ++)
641 VERIFY3U(mg_hist[i], ==, mg->mg_histogram[i]);
643 kmem_free(mg_hist, sizeof (uint64_t) * RANGE_TREE_HISTOGRAM_SIZE);
647 metaslab_group_histogram_add(metaslab_group_t *mg, metaslab_t *msp)
649 metaslab_class_t *mc = mg->mg_class;
650 uint64_t ashift = mg->mg_vd->vdev_ashift;
653 ASSERT(MUTEX_HELD(&msp->ms_lock));
654 if (msp->ms_sm == NULL)
657 mutex_enter(&mg->mg_lock);
658 for (i = 0; i < SPACE_MAP_HISTOGRAM_SIZE; i++) {
659 mg->mg_histogram[i + ashift] +=
660 msp->ms_sm->sm_phys->smp_histogram[i];
661 mc->mc_histogram[i + ashift] +=
662 msp->ms_sm->sm_phys->smp_histogram[i];
664 mutex_exit(&mg->mg_lock);
668 metaslab_group_histogram_remove(metaslab_group_t *mg, metaslab_t *msp)
670 metaslab_class_t *mc = mg->mg_class;
671 uint64_t ashift = mg->mg_vd->vdev_ashift;
674 ASSERT(MUTEX_HELD(&msp->ms_lock));
675 if (msp->ms_sm == NULL)
678 mutex_enter(&mg->mg_lock);
679 for (i = 0; i < SPACE_MAP_HISTOGRAM_SIZE; i++) {
680 ASSERT3U(mg->mg_histogram[i + ashift], >=,
681 msp->ms_sm->sm_phys->smp_histogram[i]);
682 ASSERT3U(mc->mc_histogram[i + ashift], >=,
683 msp->ms_sm->sm_phys->smp_histogram[i]);
685 mg->mg_histogram[i + ashift] -=
686 msp->ms_sm->sm_phys->smp_histogram[i];
687 mc->mc_histogram[i + ashift] -=
688 msp->ms_sm->sm_phys->smp_histogram[i];
690 mutex_exit(&mg->mg_lock);
694 metaslab_group_add(metaslab_group_t *mg, metaslab_t *msp)
696 ASSERT(msp->ms_group == NULL);
697 mutex_enter(&mg->mg_lock);
700 avl_add(&mg->mg_metaslab_tree, msp);
701 mutex_exit(&mg->mg_lock);
703 mutex_enter(&msp->ms_lock);
704 metaslab_group_histogram_add(mg, msp);
705 mutex_exit(&msp->ms_lock);
709 metaslab_group_remove(metaslab_group_t *mg, metaslab_t *msp)
711 mutex_enter(&msp->ms_lock);
712 metaslab_group_histogram_remove(mg, msp);
713 mutex_exit(&msp->ms_lock);
715 mutex_enter(&mg->mg_lock);
716 ASSERT(msp->ms_group == mg);
717 avl_remove(&mg->mg_metaslab_tree, msp);
718 msp->ms_group = NULL;
719 mutex_exit(&mg->mg_lock);
723 metaslab_group_sort(metaslab_group_t *mg, metaslab_t *msp, uint64_t weight)
726 * Although in principle the weight can be any value, in
727 * practice we do not use values in the range [1, 511].
729 ASSERT(weight >= SPA_MINBLOCKSIZE || weight == 0);
730 ASSERT(MUTEX_HELD(&msp->ms_lock));
732 mutex_enter(&mg->mg_lock);
733 ASSERT(msp->ms_group == mg);
734 avl_remove(&mg->mg_metaslab_tree, msp);
735 msp->ms_weight = weight;
736 avl_add(&mg->mg_metaslab_tree, msp);
737 mutex_exit(&mg->mg_lock);
741 * Calculate the fragmentation for a given metaslab group. We can use
742 * a simple average here since all metaslabs within the group must have
743 * the same size. The return value will be a value between 0 and 100
744 * (inclusive), or ZFS_FRAG_INVALID if less than half of the metaslab in this
745 * group have a fragmentation metric.
748 metaslab_group_fragmentation(metaslab_group_t *mg)
750 vdev_t *vd = mg->mg_vd;
751 uint64_t fragmentation = 0;
752 uint64_t valid_ms = 0;
755 for (m = 0; m < vd->vdev_ms_count; m++) {
756 metaslab_t *msp = vd->vdev_ms[m];
758 if (msp->ms_fragmentation == ZFS_FRAG_INVALID)
762 fragmentation += msp->ms_fragmentation;
765 if (valid_ms <= vd->vdev_ms_count / 2)
766 return (ZFS_FRAG_INVALID);
768 fragmentation /= valid_ms;
769 ASSERT3U(fragmentation, <=, 100);
770 return (fragmentation);
774 * Determine if a given metaslab group should skip allocations. A metaslab
775 * group should avoid allocations if its free capacity is less than the
776 * zfs_mg_noalloc_threshold or its fragmentation metric is greater than
777 * zfs_mg_fragmentation_threshold and there is at least one metaslab group
778 * that can still handle allocations. If the allocation throttle is enabled
779 * then we skip allocations to devices that have reached their maximum
780 * allocation queue depth unless the selected metaslab group is the only
781 * eligible group remaining.
784 metaslab_group_allocatable(metaslab_group_t *mg, metaslab_group_t *rotor,
787 spa_t *spa = mg->mg_vd->vdev_spa;
788 metaslab_class_t *mc = mg->mg_class;
791 * We can only consider skipping this metaslab group if it's
792 * in the normal metaslab class and there are other metaslab
793 * groups to select from. Otherwise, we always consider it eligible
796 if (mc != spa_normal_class(spa) || mc->mc_groups <= 1)
800 * If the metaslab group's mg_allocatable flag is set (see comments
801 * in metaslab_group_alloc_update() for more information) and
802 * the allocation throttle is disabled then allow allocations to this
803 * device. However, if the allocation throttle is enabled then
804 * check if we have reached our allocation limit (mg_alloc_queue_depth)
805 * to determine if we should allow allocations to this metaslab group.
806 * If all metaslab groups are no longer considered allocatable
807 * (mc_alloc_groups == 0) or we're trying to allocate the smallest
808 * gang block size then we allow allocations on this metaslab group
809 * regardless of the mg_allocatable or throttle settings.
811 if (mg->mg_allocatable) {
812 metaslab_group_t *mgp;
814 uint64_t qmax = mg->mg_max_alloc_queue_depth;
816 if (!mc->mc_alloc_throttle_enabled)
820 * If this metaslab group does not have any free space, then
821 * there is no point in looking further.
823 if (mg->mg_no_free_space)
826 qdepth = refcount_count(&mg->mg_alloc_queue_depth);
829 * If this metaslab group is below its qmax or it's
830 * the only allocatable metasable group, then attempt
831 * to allocate from it.
833 if (qdepth < qmax || mc->mc_alloc_groups == 1)
835 ASSERT3U(mc->mc_alloc_groups, >, 1);
838 * Since this metaslab group is at or over its qmax, we
839 * need to determine if there are metaslab groups after this
840 * one that might be able to handle this allocation. This is
841 * racy since we can't hold the locks for all metaslab
842 * groups at the same time when we make this check.
844 for (mgp = mg->mg_next; mgp != rotor; mgp = mgp->mg_next) {
845 qmax = mgp->mg_max_alloc_queue_depth;
847 qdepth = refcount_count(&mgp->mg_alloc_queue_depth);
850 * If there is another metaslab group that
851 * might be able to handle the allocation, then
852 * we return false so that we skip this group.
854 if (qdepth < qmax && !mgp->mg_no_free_space)
859 * We didn't find another group to handle the allocation
860 * so we can't skip this metaslab group even though
861 * we are at or over our qmax.
865 } else if (mc->mc_alloc_groups == 0 || psize == SPA_MINBLOCKSIZE) {
872 * ==========================================================================
873 * Range tree callbacks
874 * ==========================================================================
878 * Comparison function for the private size-ordered tree. Tree is sorted
879 * by size, larger sizes at the end of the tree.
882 metaslab_rangesize_compare(const void *x1, const void *x2)
884 const range_seg_t *r1 = x1;
885 const range_seg_t *r2 = x2;
886 uint64_t rs_size1 = r1->rs_end - r1->rs_start;
887 uint64_t rs_size2 = r2->rs_end - r2->rs_start;
889 int cmp = AVL_CMP(rs_size1, rs_size2);
893 return (AVL_CMP(r1->rs_start, r2->rs_start));
897 * Create any block allocator specific components. The current allocators
898 * rely on using both a size-ordered range_tree_t and an array of uint64_t's.
901 metaslab_rt_create(range_tree_t *rt, void *arg)
903 metaslab_t *msp = arg;
905 ASSERT3P(rt->rt_arg, ==, msp);
906 ASSERT(msp->ms_tree == NULL);
908 avl_create(&msp->ms_size_tree, metaslab_rangesize_compare,
909 sizeof (range_seg_t), offsetof(range_seg_t, rs_pp_node));
913 * Destroy the block allocator specific components.
916 metaslab_rt_destroy(range_tree_t *rt, void *arg)
918 metaslab_t *msp = arg;
920 ASSERT3P(rt->rt_arg, ==, msp);
921 ASSERT3P(msp->ms_tree, ==, rt);
922 ASSERT0(avl_numnodes(&msp->ms_size_tree));
924 avl_destroy(&msp->ms_size_tree);
928 metaslab_rt_add(range_tree_t *rt, range_seg_t *rs, void *arg)
930 metaslab_t *msp = arg;
932 ASSERT3P(rt->rt_arg, ==, msp);
933 ASSERT3P(msp->ms_tree, ==, rt);
934 VERIFY(!msp->ms_condensing);
935 avl_add(&msp->ms_size_tree, rs);
939 metaslab_rt_remove(range_tree_t *rt, range_seg_t *rs, void *arg)
941 metaslab_t *msp = arg;
943 ASSERT3P(rt->rt_arg, ==, msp);
944 ASSERT3P(msp->ms_tree, ==, rt);
945 VERIFY(!msp->ms_condensing);
946 avl_remove(&msp->ms_size_tree, rs);
950 metaslab_rt_vacate(range_tree_t *rt, void *arg)
952 metaslab_t *msp = arg;
954 ASSERT3P(rt->rt_arg, ==, msp);
955 ASSERT3P(msp->ms_tree, ==, rt);
958 * Normally one would walk the tree freeing nodes along the way.
959 * Since the nodes are shared with the range trees we can avoid
960 * walking all nodes and just reinitialize the avl tree. The nodes
961 * will be freed by the range tree, so we don't want to free them here.
963 avl_create(&msp->ms_size_tree, metaslab_rangesize_compare,
964 sizeof (range_seg_t), offsetof(range_seg_t, rs_pp_node));
967 static range_tree_ops_t metaslab_rt_ops = {
976 * ==========================================================================
977 * Metaslab block operations
978 * ==========================================================================
982 * Return the maximum contiguous segment within the metaslab.
985 metaslab_block_maxsize(metaslab_t *msp)
987 avl_tree_t *t = &msp->ms_size_tree;
990 if (t == NULL || (rs = avl_last(t)) == NULL)
993 return (rs->rs_end - rs->rs_start);
997 metaslab_block_alloc(metaslab_t *msp, uint64_t size)
1000 range_tree_t *rt = msp->ms_tree;
1002 VERIFY(!msp->ms_condensing);
1004 start = msp->ms_ops->msop_alloc(msp, size);
1005 if (start != -1ULL) {
1006 vdev_t *vd = msp->ms_group->mg_vd;
1008 VERIFY0(P2PHASE(start, 1ULL << vd->vdev_ashift));
1009 VERIFY0(P2PHASE(size, 1ULL << vd->vdev_ashift));
1010 VERIFY3U(range_tree_space(rt) - size, <=, msp->ms_size);
1011 range_tree_remove(rt, start, size);
1017 * ==========================================================================
1018 * Common allocator routines
1019 * ==========================================================================
1022 #if defined(WITH_FF_BLOCK_ALLOCATOR) || \
1023 defined(WITH_DF_BLOCK_ALLOCATOR) || \
1024 defined(WITH_CF_BLOCK_ALLOCATOR)
1026 * This is a helper function that can be used by the allocator to find
1027 * a suitable block to allocate. This will search the specified AVL
1028 * tree looking for a block that matches the specified criteria.
1031 metaslab_block_picker(avl_tree_t *t, uint64_t *cursor, uint64_t size,
1034 range_seg_t *rs, rsearch;
1037 rsearch.rs_start = *cursor;
1038 rsearch.rs_end = *cursor + size;
1040 rs = avl_find(t, &rsearch, &where);
1042 rs = avl_nearest(t, where, AVL_AFTER);
1044 while (rs != NULL) {
1045 uint64_t offset = P2ROUNDUP(rs->rs_start, align);
1047 if (offset + size <= rs->rs_end) {
1048 *cursor = offset + size;
1051 rs = AVL_NEXT(t, rs);
1055 * If we know we've searched the whole map (*cursor == 0), give up.
1056 * Otherwise, reset the cursor to the beginning and try again.
1062 return (metaslab_block_picker(t, cursor, size, align));
1064 #endif /* WITH_FF/DF/CF_BLOCK_ALLOCATOR */
1066 #if defined(WITH_FF_BLOCK_ALLOCATOR)
1068 * ==========================================================================
1069 * The first-fit block allocator
1070 * ==========================================================================
1073 metaslab_ff_alloc(metaslab_t *msp, uint64_t size)
1076 * Find the largest power of 2 block size that evenly divides the
1077 * requested size. This is used to try to allocate blocks with similar
1078 * alignment from the same area of the metaslab (i.e. same cursor
1079 * bucket) but it does not guarantee that other allocations sizes
1080 * may exist in the same region.
1082 uint64_t align = size & -size;
1083 uint64_t *cursor = &msp->ms_lbas[highbit64(align) - 1];
1084 avl_tree_t *t = &msp->ms_tree->rt_root;
1086 return (metaslab_block_picker(t, cursor, size, align));
1089 static metaslab_ops_t metaslab_ff_ops = {
1093 metaslab_ops_t *zfs_metaslab_ops = &metaslab_ff_ops;
1094 #endif /* WITH_FF_BLOCK_ALLOCATOR */
1096 #if defined(WITH_DF_BLOCK_ALLOCATOR)
1098 * ==========================================================================
1099 * Dynamic block allocator -
1100 * Uses the first fit allocation scheme until space get low and then
1101 * adjusts to a best fit allocation method. Uses metaslab_df_alloc_threshold
1102 * and metaslab_df_free_pct to determine when to switch the allocation scheme.
1103 * ==========================================================================
1106 metaslab_df_alloc(metaslab_t *msp, uint64_t size)
1109 * Find the largest power of 2 block size that evenly divides the
1110 * requested size. This is used to try to allocate blocks with similar
1111 * alignment from the same area of the metaslab (i.e. same cursor
1112 * bucket) but it does not guarantee that other allocations sizes
1113 * may exist in the same region.
1115 uint64_t align = size & -size;
1116 uint64_t *cursor = &msp->ms_lbas[highbit64(align) - 1];
1117 range_tree_t *rt = msp->ms_tree;
1118 avl_tree_t *t = &rt->rt_root;
1119 uint64_t max_size = metaslab_block_maxsize(msp);
1120 int free_pct = range_tree_space(rt) * 100 / msp->ms_size;
1122 ASSERT(MUTEX_HELD(&msp->ms_lock));
1123 ASSERT3U(avl_numnodes(t), ==, avl_numnodes(&msp->ms_size_tree));
1125 if (max_size < size)
1129 * If we're running low on space switch to using the size
1130 * sorted AVL tree (best-fit).
1132 if (max_size < metaslab_df_alloc_threshold ||
1133 free_pct < metaslab_df_free_pct) {
1134 t = &msp->ms_size_tree;
1138 return (metaslab_block_picker(t, cursor, size, 1ULL));
1141 static metaslab_ops_t metaslab_df_ops = {
1145 metaslab_ops_t *zfs_metaslab_ops = &metaslab_df_ops;
1146 #endif /* WITH_DF_BLOCK_ALLOCATOR */
1148 #if defined(WITH_CF_BLOCK_ALLOCATOR)
1150 * ==========================================================================
1151 * Cursor fit block allocator -
1152 * Select the largest region in the metaslab, set the cursor to the beginning
1153 * of the range and the cursor_end to the end of the range. As allocations
1154 * are made advance the cursor. Continue allocating from the cursor until
1155 * the range is exhausted and then find a new range.
1156 * ==========================================================================
1159 metaslab_cf_alloc(metaslab_t *msp, uint64_t size)
1161 range_tree_t *rt = msp->ms_tree;
1162 avl_tree_t *t = &msp->ms_size_tree;
1163 uint64_t *cursor = &msp->ms_lbas[0];
1164 uint64_t *cursor_end = &msp->ms_lbas[1];
1165 uint64_t offset = 0;
1167 ASSERT(MUTEX_HELD(&msp->ms_lock));
1168 ASSERT3U(avl_numnodes(t), ==, avl_numnodes(&rt->rt_root));
1170 ASSERT3U(*cursor_end, >=, *cursor);
1172 if ((*cursor + size) > *cursor_end) {
1175 rs = avl_last(&msp->ms_size_tree);
1176 if (rs == NULL || (rs->rs_end - rs->rs_start) < size)
1179 *cursor = rs->rs_start;
1180 *cursor_end = rs->rs_end;
1189 static metaslab_ops_t metaslab_cf_ops = {
1193 metaslab_ops_t *zfs_metaslab_ops = &metaslab_cf_ops;
1194 #endif /* WITH_CF_BLOCK_ALLOCATOR */
1196 #if defined(WITH_NDF_BLOCK_ALLOCATOR)
1198 * ==========================================================================
1199 * New dynamic fit allocator -
1200 * Select a region that is large enough to allocate 2^metaslab_ndf_clump_shift
1201 * contiguous blocks. If no region is found then just use the largest segment
1203 * ==========================================================================
1207 * Determines desired number of contiguous blocks (2^metaslab_ndf_clump_shift)
1208 * to request from the allocator.
1210 uint64_t metaslab_ndf_clump_shift = 4;
1213 metaslab_ndf_alloc(metaslab_t *msp, uint64_t size)
1215 avl_tree_t *t = &msp->ms_tree->rt_root;
1217 range_seg_t *rs, rsearch;
1218 uint64_t hbit = highbit64(size);
1219 uint64_t *cursor = &msp->ms_lbas[hbit - 1];
1220 uint64_t max_size = metaslab_block_maxsize(msp);
1222 ASSERT(MUTEX_HELD(&msp->ms_lock));
1223 ASSERT3U(avl_numnodes(t), ==, avl_numnodes(&msp->ms_size_tree));
1225 if (max_size < size)
1228 rsearch.rs_start = *cursor;
1229 rsearch.rs_end = *cursor + size;
1231 rs = avl_find(t, &rsearch, &where);
1232 if (rs == NULL || (rs->rs_end - rs->rs_start) < size) {
1233 t = &msp->ms_size_tree;
1235 rsearch.rs_start = 0;
1236 rsearch.rs_end = MIN(max_size,
1237 1ULL << (hbit + metaslab_ndf_clump_shift));
1238 rs = avl_find(t, &rsearch, &where);
1240 rs = avl_nearest(t, where, AVL_AFTER);
1244 if ((rs->rs_end - rs->rs_start) >= size) {
1245 *cursor = rs->rs_start + size;
1246 return (rs->rs_start);
1251 static metaslab_ops_t metaslab_ndf_ops = {
1255 metaslab_ops_t *zfs_metaslab_ops = &metaslab_ndf_ops;
1256 #endif /* WITH_NDF_BLOCK_ALLOCATOR */
1260 * ==========================================================================
1262 * ==========================================================================
1266 * Wait for any in-progress metaslab loads to complete.
1269 metaslab_load_wait(metaslab_t *msp)
1271 ASSERT(MUTEX_HELD(&msp->ms_lock));
1273 while (msp->ms_loading) {
1274 ASSERT(!msp->ms_loaded);
1275 cv_wait(&msp->ms_load_cv, &msp->ms_lock);
1280 metaslab_load(metaslab_t *msp)
1285 ASSERT(MUTEX_HELD(&msp->ms_lock));
1286 ASSERT(!msp->ms_loaded);
1287 ASSERT(!msp->ms_loading);
1289 msp->ms_loading = B_TRUE;
1292 * If the space map has not been allocated yet, then treat
1293 * all the space in the metaslab as free and add it to the
1296 if (msp->ms_sm != NULL)
1297 error = space_map_load(msp->ms_sm, msp->ms_tree, SM_FREE);
1299 range_tree_add(msp->ms_tree, msp->ms_start, msp->ms_size);
1301 msp->ms_loaded = (error == 0);
1302 msp->ms_loading = B_FALSE;
1304 if (msp->ms_loaded) {
1305 for (t = 0; t < TXG_DEFER_SIZE; t++) {
1306 range_tree_walk(msp->ms_defertree[t],
1307 range_tree_remove, msp->ms_tree);
1310 cv_broadcast(&msp->ms_load_cv);
1315 metaslab_unload(metaslab_t *msp)
1317 ASSERT(MUTEX_HELD(&msp->ms_lock));
1318 range_tree_vacate(msp->ms_tree, NULL, NULL);
1319 msp->ms_loaded = B_FALSE;
1320 msp->ms_weight &= ~METASLAB_ACTIVE_MASK;
1324 metaslab_init(metaslab_group_t *mg, uint64_t id, uint64_t object, uint64_t txg,
1327 vdev_t *vd = mg->mg_vd;
1328 objset_t *mos = vd->vdev_spa->spa_meta_objset;
1332 ms = kmem_zalloc(sizeof (metaslab_t), KM_SLEEP);
1333 mutex_init(&ms->ms_lock, NULL, MUTEX_DEFAULT, NULL);
1334 cv_init(&ms->ms_load_cv, NULL, CV_DEFAULT, NULL);
1336 ms->ms_start = id << vd->vdev_ms_shift;
1337 ms->ms_size = 1ULL << vd->vdev_ms_shift;
1340 * We only open space map objects that already exist. All others
1341 * will be opened when we finally allocate an object for it.
1344 error = space_map_open(&ms->ms_sm, mos, object, ms->ms_start,
1345 ms->ms_size, vd->vdev_ashift, &ms->ms_lock);
1348 kmem_free(ms, sizeof (metaslab_t));
1352 ASSERT(ms->ms_sm != NULL);
1356 * We create the main range tree here, but we don't create the
1357 * alloctree and freetree until metaslab_sync_done(). This serves
1358 * two purposes: it allows metaslab_sync_done() to detect the
1359 * addition of new space; and for debugging, it ensures that we'd
1360 * data fault on any attempt to use this metaslab before it's ready.
1362 ms->ms_tree = range_tree_create(&metaslab_rt_ops, ms, &ms->ms_lock);
1363 metaslab_group_add(mg, ms);
1365 ms->ms_fragmentation = metaslab_fragmentation(ms);
1366 ms->ms_ops = mg->mg_class->mc_ops;
1369 * If we're opening an existing pool (txg == 0) or creating
1370 * a new one (txg == TXG_INITIAL), all space is available now.
1371 * If we're adding space to an existing pool, the new space
1372 * does not become available until after this txg has synced.
1374 if (txg <= TXG_INITIAL)
1375 metaslab_sync_done(ms, 0);
1378 * If metaslab_debug_load is set and we're initializing a metaslab
1379 * that has an allocated space_map object then load the its space
1380 * map so that can verify frees.
1382 if (metaslab_debug_load && ms->ms_sm != NULL) {
1383 mutex_enter(&ms->ms_lock);
1384 VERIFY0(metaslab_load(ms));
1385 mutex_exit(&ms->ms_lock);
1389 vdev_dirty(vd, 0, NULL, txg);
1390 vdev_dirty(vd, VDD_METASLAB, ms, txg);
1399 metaslab_fini(metaslab_t *msp)
1403 metaslab_group_t *mg = msp->ms_group;
1405 metaslab_group_remove(mg, msp);
1407 mutex_enter(&msp->ms_lock);
1409 VERIFY(msp->ms_group == NULL);
1410 vdev_space_update(mg->mg_vd, -space_map_allocated(msp->ms_sm),
1412 space_map_close(msp->ms_sm);
1414 metaslab_unload(msp);
1415 range_tree_destroy(msp->ms_tree);
1417 for (t = 0; t < TXG_SIZE; t++) {
1418 range_tree_destroy(msp->ms_alloctree[t]);
1419 range_tree_destroy(msp->ms_freetree[t]);
1422 for (t = 0; t < TXG_DEFER_SIZE; t++) {
1423 range_tree_destroy(msp->ms_defertree[t]);
1426 ASSERT0(msp->ms_deferspace);
1428 mutex_exit(&msp->ms_lock);
1429 cv_destroy(&msp->ms_load_cv);
1430 mutex_destroy(&msp->ms_lock);
1432 kmem_free(msp, sizeof (metaslab_t));
1435 #define FRAGMENTATION_TABLE_SIZE 17
1438 * This table defines a segment size based fragmentation metric that will
1439 * allow each metaslab to derive its own fragmentation value. This is done
1440 * by calculating the space in each bucket of the spacemap histogram and
1441 * multiplying that by the fragmetation metric in this table. Doing
1442 * this for all buckets and dividing it by the total amount of free
1443 * space in this metaslab (i.e. the total free space in all buckets) gives
1444 * us the fragmentation metric. This means that a high fragmentation metric
1445 * equates to most of the free space being comprised of small segments.
1446 * Conversely, if the metric is low, then most of the free space is in
1447 * large segments. A 10% change in fragmentation equates to approximately
1448 * double the number of segments.
1450 * This table defines 0% fragmented space using 16MB segments. Testing has
1451 * shown that segments that are greater than or equal to 16MB do not suffer
1452 * from drastic performance problems. Using this value, we derive the rest
1453 * of the table. Since the fragmentation value is never stored on disk, it
1454 * is possible to change these calculations in the future.
1456 int zfs_frag_table[FRAGMENTATION_TABLE_SIZE] = {
1476 * Calclate the metaslab's fragmentation metric. A return value
1477 * of ZFS_FRAG_INVALID means that the metaslab has not been upgraded and does
1478 * not support this metric. Otherwise, the return value should be in the
1482 metaslab_fragmentation(metaslab_t *msp)
1484 spa_t *spa = msp->ms_group->mg_vd->vdev_spa;
1485 uint64_t fragmentation = 0;
1487 boolean_t feature_enabled = spa_feature_is_enabled(spa,
1488 SPA_FEATURE_SPACEMAP_HISTOGRAM);
1491 if (!feature_enabled)
1492 return (ZFS_FRAG_INVALID);
1495 * A null space map means that the entire metaslab is free
1496 * and thus is not fragmented.
1498 if (msp->ms_sm == NULL)
1502 * If this metaslab's space_map has not been upgraded, flag it
1503 * so that we upgrade next time we encounter it.
1505 if (msp->ms_sm->sm_dbuf->db_size != sizeof (space_map_phys_t)) {
1506 vdev_t *vd = msp->ms_group->mg_vd;
1508 if (spa_writeable(vd->vdev_spa)) {
1509 uint64_t txg = spa_syncing_txg(spa);
1511 msp->ms_condense_wanted = B_TRUE;
1512 vdev_dirty(vd, VDD_METASLAB, msp, txg + 1);
1513 spa_dbgmsg(spa, "txg %llu, requesting force condense: "
1514 "msp %p, vd %p", txg, msp, vd);
1516 return (ZFS_FRAG_INVALID);
1519 for (i = 0; i < SPACE_MAP_HISTOGRAM_SIZE; i++) {
1521 uint8_t shift = msp->ms_sm->sm_shift;
1522 int idx = MIN(shift - SPA_MINBLOCKSHIFT + i,
1523 FRAGMENTATION_TABLE_SIZE - 1);
1525 if (msp->ms_sm->sm_phys->smp_histogram[i] == 0)
1528 space = msp->ms_sm->sm_phys->smp_histogram[i] << (i + shift);
1531 ASSERT3U(idx, <, FRAGMENTATION_TABLE_SIZE);
1532 fragmentation += space * zfs_frag_table[idx];
1536 fragmentation /= total;
1537 ASSERT3U(fragmentation, <=, 100);
1538 return (fragmentation);
1542 * Compute a weight -- a selection preference value -- for the given metaslab.
1543 * This is based on the amount of free space, the level of fragmentation,
1544 * the LBA range, and whether the metaslab is loaded.
1547 metaslab_weight(metaslab_t *msp)
1549 metaslab_group_t *mg = msp->ms_group;
1550 vdev_t *vd = mg->mg_vd;
1551 uint64_t weight, space;
1553 ASSERT(MUTEX_HELD(&msp->ms_lock));
1556 * This vdev is in the process of being removed so there is nothing
1557 * for us to do here.
1559 if (vd->vdev_removing) {
1560 ASSERT0(space_map_allocated(msp->ms_sm));
1561 ASSERT0(vd->vdev_ms_shift);
1566 * The baseline weight is the metaslab's free space.
1568 space = msp->ms_size - space_map_allocated(msp->ms_sm);
1570 msp->ms_fragmentation = metaslab_fragmentation(msp);
1571 if (metaslab_fragmentation_factor_enabled &&
1572 msp->ms_fragmentation != ZFS_FRAG_INVALID) {
1574 * Use the fragmentation information to inversely scale
1575 * down the baseline weight. We need to ensure that we
1576 * don't exclude this metaslab completely when it's 100%
1577 * fragmented. To avoid this we reduce the fragmented value
1580 space = (space * (100 - (msp->ms_fragmentation - 1))) / 100;
1583 * If space < SPA_MINBLOCKSIZE, then we will not allocate from
1584 * this metaslab again. The fragmentation metric may have
1585 * decreased the space to something smaller than
1586 * SPA_MINBLOCKSIZE, so reset the space to SPA_MINBLOCKSIZE
1587 * so that we can consume any remaining space.
1589 if (space > 0 && space < SPA_MINBLOCKSIZE)
1590 space = SPA_MINBLOCKSIZE;
1595 * Modern disks have uniform bit density and constant angular velocity.
1596 * Therefore, the outer recording zones are faster (higher bandwidth)
1597 * than the inner zones by the ratio of outer to inner track diameter,
1598 * which is typically around 2:1. We account for this by assigning
1599 * higher weight to lower metaslabs (multiplier ranging from 2x to 1x).
1600 * In effect, this means that we'll select the metaslab with the most
1601 * free bandwidth rather than simply the one with the most free space.
1603 if (!vd->vdev_nonrot && metaslab_lba_weighting_enabled) {
1604 weight = 2 * weight - (msp->ms_id * weight) / vd->vdev_ms_count;
1605 ASSERT(weight >= space && weight <= 2 * space);
1609 * If this metaslab is one we're actively using, adjust its
1610 * weight to make it preferable to any inactive metaslab so
1611 * we'll polish it off. If the fragmentation on this metaslab
1612 * has exceed our threshold, then don't mark it active.
1614 if (msp->ms_loaded && msp->ms_fragmentation != ZFS_FRAG_INVALID &&
1615 msp->ms_fragmentation <= zfs_metaslab_fragmentation_threshold) {
1616 weight |= (msp->ms_weight & METASLAB_ACTIVE_MASK);
1623 metaslab_activate(metaslab_t *msp, uint64_t activation_weight)
1625 ASSERT(MUTEX_HELD(&msp->ms_lock));
1627 if ((msp->ms_weight & METASLAB_ACTIVE_MASK) == 0) {
1628 metaslab_load_wait(msp);
1629 if (!msp->ms_loaded) {
1630 int error = metaslab_load(msp);
1632 metaslab_group_sort(msp->ms_group, msp, 0);
1637 metaslab_group_sort(msp->ms_group, msp,
1638 msp->ms_weight | activation_weight);
1640 ASSERT(msp->ms_loaded);
1641 ASSERT(msp->ms_weight & METASLAB_ACTIVE_MASK);
1647 metaslab_passivate(metaslab_t *msp, uint64_t size)
1650 * If size < SPA_MINBLOCKSIZE, then we will not allocate from
1651 * this metaslab again. In that case, it had better be empty,
1652 * or we would be leaving space on the table.
1654 ASSERT(size >= SPA_MINBLOCKSIZE || range_tree_space(msp->ms_tree) == 0);
1655 metaslab_group_sort(msp->ms_group, msp, MIN(msp->ms_weight, size));
1656 ASSERT((msp->ms_weight & METASLAB_ACTIVE_MASK) == 0);
1660 metaslab_preload(void *arg)
1662 metaslab_t *msp = arg;
1663 spa_t *spa = msp->ms_group->mg_vd->vdev_spa;
1664 fstrans_cookie_t cookie = spl_fstrans_mark();
1666 ASSERT(!MUTEX_HELD(&msp->ms_group->mg_lock));
1668 mutex_enter(&msp->ms_lock);
1669 metaslab_load_wait(msp);
1670 if (!msp->ms_loaded)
1671 (void) metaslab_load(msp);
1674 * Set the ms_access_txg value so that we don't unload it right away.
1676 msp->ms_access_txg = spa_syncing_txg(spa) + metaslab_unload_delay + 1;
1677 mutex_exit(&msp->ms_lock);
1678 spl_fstrans_unmark(cookie);
1682 metaslab_group_preload(metaslab_group_t *mg)
1684 spa_t *spa = mg->mg_vd->vdev_spa;
1686 avl_tree_t *t = &mg->mg_metaslab_tree;
1689 if (spa_shutting_down(spa) || !metaslab_preload_enabled) {
1690 taskq_wait_outstanding(mg->mg_taskq, 0);
1694 mutex_enter(&mg->mg_lock);
1696 * Load the next potential metaslabs
1699 while (msp != NULL) {
1700 metaslab_t *msp_next = AVL_NEXT(t, msp);
1703 * We preload only the maximum number of metaslabs specified
1704 * by metaslab_preload_limit. If a metaslab is being forced
1705 * to condense then we preload it too. This will ensure
1706 * that force condensing happens in the next txg.
1708 if (++m > metaslab_preload_limit && !msp->ms_condense_wanted) {
1714 * We must drop the metaslab group lock here to preserve
1715 * lock ordering with the ms_lock (when grabbing both
1716 * the mg_lock and the ms_lock, the ms_lock must be taken
1717 * first). As a result, it is possible that the ordering
1718 * of the metaslabs within the avl tree may change before
1719 * we reacquire the lock. The metaslab cannot be removed from
1720 * the tree while we're in syncing context so it is safe to
1721 * drop the mg_lock here. If the metaslabs are reordered
1722 * nothing will break -- we just may end up loading a
1723 * less than optimal one.
1725 mutex_exit(&mg->mg_lock);
1726 VERIFY(taskq_dispatch(mg->mg_taskq, metaslab_preload,
1727 msp, TQ_SLEEP) != TASKQID_INVALID);
1728 mutex_enter(&mg->mg_lock);
1731 mutex_exit(&mg->mg_lock);
1735 * Determine if the space map's on-disk footprint is past our tolerance
1736 * for inefficiency. We would like to use the following criteria to make
1739 * 1. The size of the space map object should not dramatically increase as a
1740 * result of writing out the free space range tree.
1742 * 2. The minimal on-disk space map representation is zfs_condense_pct/100
1743 * times the size than the free space range tree representation
1744 * (i.e. zfs_condense_pct = 110 and in-core = 1MB, minimal = 1.1.MB).
1746 * 3. The on-disk size of the space map should actually decrease.
1748 * Checking the first condition is tricky since we don't want to walk
1749 * the entire AVL tree calculating the estimated on-disk size. Instead we
1750 * use the size-ordered range tree in the metaslab and calculate the
1751 * size required to write out the largest segment in our free tree. If the
1752 * size required to represent that segment on disk is larger than the space
1753 * map object then we avoid condensing this map.
1755 * To determine the second criterion we use a best-case estimate and assume
1756 * each segment can be represented on-disk as a single 64-bit entry. We refer
1757 * to this best-case estimate as the space map's minimal form.
1759 * Unfortunately, we cannot compute the on-disk size of the space map in this
1760 * context because we cannot accurately compute the effects of compression, etc.
1761 * Instead, we apply the heuristic described in the block comment for
1762 * zfs_metaslab_condense_block_threshold - we only condense if the space used
1763 * is greater than a threshold number of blocks.
1766 metaslab_should_condense(metaslab_t *msp)
1768 space_map_t *sm = msp->ms_sm;
1770 uint64_t size, entries, segsz, object_size, optimal_size, record_size;
1771 dmu_object_info_t doi;
1772 uint64_t vdev_blocksize = 1 << msp->ms_group->mg_vd->vdev_ashift;
1774 ASSERT(MUTEX_HELD(&msp->ms_lock));
1775 ASSERT(msp->ms_loaded);
1778 * Use the ms_size_tree range tree, which is ordered by size, to
1779 * obtain the largest segment in the free tree. We always condense
1780 * metaslabs that are empty and metaslabs for which a condense
1781 * request has been made.
1783 rs = avl_last(&msp->ms_size_tree);
1784 if (rs == NULL || msp->ms_condense_wanted)
1788 * Calculate the number of 64-bit entries this segment would
1789 * require when written to disk. If this single segment would be
1790 * larger on-disk than the entire current on-disk structure, then
1791 * clearly condensing will increase the on-disk structure size.
1793 size = (rs->rs_end - rs->rs_start) >> sm->sm_shift;
1794 entries = size / (MIN(size, SM_RUN_MAX));
1795 segsz = entries * sizeof (uint64_t);
1797 optimal_size = sizeof (uint64_t) * avl_numnodes(&msp->ms_tree->rt_root);
1798 object_size = space_map_length(msp->ms_sm);
1800 dmu_object_info_from_db(sm->sm_dbuf, &doi);
1801 record_size = MAX(doi.doi_data_block_size, vdev_blocksize);
1803 return (segsz <= object_size &&
1804 object_size >= (optimal_size * zfs_condense_pct / 100) &&
1805 object_size > zfs_metaslab_condense_block_threshold * record_size);
1809 * Condense the on-disk space map representation to its minimized form.
1810 * The minimized form consists of a small number of allocations followed by
1811 * the entries of the free range tree.
1814 metaslab_condense(metaslab_t *msp, uint64_t txg, dmu_tx_t *tx)
1816 spa_t *spa = msp->ms_group->mg_vd->vdev_spa;
1817 range_tree_t *freetree = msp->ms_freetree[txg & TXG_MASK];
1818 range_tree_t *condense_tree;
1819 space_map_t *sm = msp->ms_sm;
1822 ASSERT(MUTEX_HELD(&msp->ms_lock));
1823 ASSERT3U(spa_sync_pass(spa), ==, 1);
1824 ASSERT(msp->ms_loaded);
1827 spa_dbgmsg(spa, "condensing: txg %llu, msp[%llu] %p, vdev id %llu, "
1828 "spa %s, smp size %llu, segments %lu, forcing condense=%s", txg,
1829 msp->ms_id, msp, msp->ms_group->mg_vd->vdev_id,
1830 msp->ms_group->mg_vd->vdev_spa->spa_name,
1831 space_map_length(msp->ms_sm), avl_numnodes(&msp->ms_tree->rt_root),
1832 msp->ms_condense_wanted ? "TRUE" : "FALSE");
1834 msp->ms_condense_wanted = B_FALSE;
1837 * Create an range tree that is 100% allocated. We remove segments
1838 * that have been freed in this txg, any deferred frees that exist,
1839 * and any allocation in the future. Removing segments should be
1840 * a relatively inexpensive operation since we expect these trees to
1841 * have a small number of nodes.
1843 condense_tree = range_tree_create(NULL, NULL, &msp->ms_lock);
1844 range_tree_add(condense_tree, msp->ms_start, msp->ms_size);
1847 * Remove what's been freed in this txg from the condense_tree.
1848 * Since we're in sync_pass 1, we know that all the frees from
1849 * this txg are in the freetree.
1851 range_tree_walk(freetree, range_tree_remove, condense_tree);
1853 for (t = 0; t < TXG_DEFER_SIZE; t++) {
1854 range_tree_walk(msp->ms_defertree[t],
1855 range_tree_remove, condense_tree);
1858 for (t = 1; t < TXG_CONCURRENT_STATES; t++) {
1859 range_tree_walk(msp->ms_alloctree[(txg + t) & TXG_MASK],
1860 range_tree_remove, condense_tree);
1864 * We're about to drop the metaslab's lock thus allowing
1865 * other consumers to change it's content. Set the
1866 * metaslab's ms_condensing flag to ensure that
1867 * allocations on this metaslab do not occur while we're
1868 * in the middle of committing it to disk. This is only critical
1869 * for the ms_tree as all other range trees use per txg
1870 * views of their content.
1872 msp->ms_condensing = B_TRUE;
1874 mutex_exit(&msp->ms_lock);
1875 space_map_truncate(sm, tx);
1876 mutex_enter(&msp->ms_lock);
1879 * While we would ideally like to create a space_map representation
1880 * that consists only of allocation records, doing so can be
1881 * prohibitively expensive because the in-core free tree can be
1882 * large, and therefore computationally expensive to subtract
1883 * from the condense_tree. Instead we sync out two trees, a cheap
1884 * allocation only tree followed by the in-core free tree. While not
1885 * optimal, this is typically close to optimal, and much cheaper to
1888 space_map_write(sm, condense_tree, SM_ALLOC, tx);
1889 range_tree_vacate(condense_tree, NULL, NULL);
1890 range_tree_destroy(condense_tree);
1892 space_map_write(sm, msp->ms_tree, SM_FREE, tx);
1893 msp->ms_condensing = B_FALSE;
1897 * Write a metaslab to disk in the context of the specified transaction group.
1900 metaslab_sync(metaslab_t *msp, uint64_t txg)
1902 metaslab_group_t *mg = msp->ms_group;
1903 vdev_t *vd = mg->mg_vd;
1904 spa_t *spa = vd->vdev_spa;
1905 objset_t *mos = spa_meta_objset(spa);
1906 range_tree_t *alloctree = msp->ms_alloctree[txg & TXG_MASK];
1907 range_tree_t **freetree = &msp->ms_freetree[txg & TXG_MASK];
1908 range_tree_t **freed_tree =
1909 &msp->ms_freetree[TXG_CLEAN(txg) & TXG_MASK];
1911 uint64_t object = space_map_object(msp->ms_sm);
1913 ASSERT(!vd->vdev_ishole);
1916 * This metaslab has just been added so there's no work to do now.
1918 if (*freetree == NULL) {
1919 ASSERT3P(alloctree, ==, NULL);
1923 ASSERT3P(alloctree, !=, NULL);
1924 ASSERT3P(*freetree, !=, NULL);
1925 ASSERT3P(*freed_tree, !=, NULL);
1928 * Normally, we don't want to process a metaslab if there
1929 * are no allocations or frees to perform. However, if the metaslab
1930 * is being forced to condense we need to let it through.
1932 if (range_tree_space(alloctree) == 0 &&
1933 range_tree_space(*freetree) == 0 &&
1934 !msp->ms_condense_wanted)
1938 * The only state that can actually be changing concurrently with
1939 * metaslab_sync() is the metaslab's ms_tree. No other thread can
1940 * be modifying this txg's alloctree, freetree, freed_tree, or
1941 * space_map_phys_t. Therefore, we only hold ms_lock to satify
1942 * space_map ASSERTs. We drop it whenever we call into the DMU,
1943 * because the DMU can call down to us (e.g. via zio_free()) at
1947 tx = dmu_tx_create_assigned(spa_get_dsl(spa), txg);
1949 if (msp->ms_sm == NULL) {
1950 uint64_t new_object;
1952 new_object = space_map_alloc(mos, tx);
1953 VERIFY3U(new_object, !=, 0);
1955 VERIFY0(space_map_open(&msp->ms_sm, mos, new_object,
1956 msp->ms_start, msp->ms_size, vd->vdev_ashift,
1958 ASSERT(msp->ms_sm != NULL);
1961 mutex_enter(&msp->ms_lock);
1964 * Note: metaslab_condense() clears the space_map's histogram.
1965 * Therefore we muse verify and remove this histogram before
1968 metaslab_group_histogram_verify(mg);
1969 metaslab_class_histogram_verify(mg->mg_class);
1970 metaslab_group_histogram_remove(mg, msp);
1972 if (msp->ms_loaded && spa_sync_pass(spa) == 1 &&
1973 metaslab_should_condense(msp)) {
1974 metaslab_condense(msp, txg, tx);
1976 space_map_write(msp->ms_sm, alloctree, SM_ALLOC, tx);
1977 space_map_write(msp->ms_sm, *freetree, SM_FREE, tx);
1980 if (msp->ms_loaded) {
1982 * When the space map is loaded, we have an accruate
1983 * histogram in the range tree. This gives us an opportunity
1984 * to bring the space map's histogram up-to-date so we clear
1985 * it first before updating it.
1987 space_map_histogram_clear(msp->ms_sm);
1988 space_map_histogram_add(msp->ms_sm, msp->ms_tree, tx);
1991 * Since the space map is not loaded we simply update the
1992 * exisiting histogram with what was freed in this txg. This
1993 * means that the on-disk histogram may not have an accurate
1994 * view of the free space but it's close enough to allow
1995 * us to make allocation decisions.
1997 space_map_histogram_add(msp->ms_sm, *freetree, tx);
1999 metaslab_group_histogram_add(mg, msp);
2000 metaslab_group_histogram_verify(mg);
2001 metaslab_class_histogram_verify(mg->mg_class);
2004 * For sync pass 1, we avoid traversing this txg's free range tree
2005 * and instead will just swap the pointers for freetree and
2006 * freed_tree. We can safely do this since the freed_tree is
2007 * guaranteed to be empty on the initial pass.
2009 if (spa_sync_pass(spa) == 1) {
2010 range_tree_swap(freetree, freed_tree);
2012 range_tree_vacate(*freetree, range_tree_add, *freed_tree);
2014 range_tree_vacate(alloctree, NULL, NULL);
2016 ASSERT0(range_tree_space(msp->ms_alloctree[txg & TXG_MASK]));
2017 ASSERT0(range_tree_space(msp->ms_freetree[txg & TXG_MASK]));
2019 mutex_exit(&msp->ms_lock);
2021 if (object != space_map_object(msp->ms_sm)) {
2022 object = space_map_object(msp->ms_sm);
2023 dmu_write(mos, vd->vdev_ms_array, sizeof (uint64_t) *
2024 msp->ms_id, sizeof (uint64_t), &object, tx);
2030 * Called after a transaction group has completely synced to mark
2031 * all of the metaslab's free space as usable.
2034 metaslab_sync_done(metaslab_t *msp, uint64_t txg)
2036 metaslab_group_t *mg = msp->ms_group;
2037 vdev_t *vd = mg->mg_vd;
2038 range_tree_t **freed_tree;
2039 range_tree_t **defer_tree;
2040 int64_t alloc_delta, defer_delta;
2043 ASSERT(!vd->vdev_ishole);
2045 mutex_enter(&msp->ms_lock);
2048 * If this metaslab is just becoming available, initialize its
2049 * alloctrees, freetrees, and defertree and add its capacity to
2052 if (msp->ms_freetree[TXG_CLEAN(txg) & TXG_MASK] == NULL) {
2053 for (t = 0; t < TXG_SIZE; t++) {
2054 ASSERT(msp->ms_alloctree[t] == NULL);
2055 ASSERT(msp->ms_freetree[t] == NULL);
2057 msp->ms_alloctree[t] = range_tree_create(NULL, msp,
2059 msp->ms_freetree[t] = range_tree_create(NULL, msp,
2063 for (t = 0; t < TXG_DEFER_SIZE; t++) {
2064 ASSERT(msp->ms_defertree[t] == NULL);
2066 msp->ms_defertree[t] = range_tree_create(NULL, msp,
2070 vdev_space_update(vd, 0, 0, msp->ms_size);
2073 freed_tree = &msp->ms_freetree[TXG_CLEAN(txg) & TXG_MASK];
2074 defer_tree = &msp->ms_defertree[txg % TXG_DEFER_SIZE];
2076 alloc_delta = space_map_alloc_delta(msp->ms_sm);
2077 defer_delta = range_tree_space(*freed_tree) -
2078 range_tree_space(*defer_tree);
2080 vdev_space_update(vd, alloc_delta + defer_delta, defer_delta, 0);
2082 ASSERT0(range_tree_space(msp->ms_alloctree[txg & TXG_MASK]));
2083 ASSERT0(range_tree_space(msp->ms_freetree[txg & TXG_MASK]));
2086 * If there's a metaslab_load() in progress, wait for it to complete
2087 * so that we have a consistent view of the in-core space map.
2089 metaslab_load_wait(msp);
2092 * Move the frees from the defer_tree back to the free
2093 * range tree (if it's loaded). Swap the freed_tree and the
2094 * defer_tree -- this is safe to do because we've just emptied out
2097 range_tree_vacate(*defer_tree,
2098 msp->ms_loaded ? range_tree_add : NULL, msp->ms_tree);
2099 range_tree_swap(freed_tree, defer_tree);
2101 space_map_update(msp->ms_sm);
2103 msp->ms_deferspace += defer_delta;
2104 ASSERT3S(msp->ms_deferspace, >=, 0);
2105 ASSERT3S(msp->ms_deferspace, <=, msp->ms_size);
2106 if (msp->ms_deferspace != 0) {
2108 * Keep syncing this metaslab until all deferred frees
2109 * are back in circulation.
2111 vdev_dirty(vd, VDD_METASLAB, msp, txg + 1);
2114 if (msp->ms_loaded && msp->ms_access_txg < txg) {
2115 for (t = 1; t < TXG_CONCURRENT_STATES; t++) {
2116 VERIFY0(range_tree_space(
2117 msp->ms_alloctree[(txg + t) & TXG_MASK]));
2120 if (!metaslab_debug_unload)
2121 metaslab_unload(msp);
2124 metaslab_group_sort(mg, msp, metaslab_weight(msp));
2125 mutex_exit(&msp->ms_lock);
2129 metaslab_sync_reassess(metaslab_group_t *mg)
2131 metaslab_group_alloc_update(mg);
2132 mg->mg_fragmentation = metaslab_group_fragmentation(mg);
2135 * Preload the next potential metaslabs
2137 metaslab_group_preload(mg);
2141 metaslab_distance(metaslab_t *msp, dva_t *dva)
2143 uint64_t ms_shift = msp->ms_group->mg_vd->vdev_ms_shift;
2144 uint64_t offset = DVA_GET_OFFSET(dva) >> ms_shift;
2145 uint64_t start = msp->ms_id;
2147 if (msp->ms_group->mg_vd->vdev_id != DVA_GET_VDEV(dva))
2148 return (1ULL << 63);
2151 return ((start - offset) << ms_shift);
2153 return ((offset - start) << ms_shift);
2158 * ==========================================================================
2159 * Metaslab block operations
2160 * ==========================================================================
2164 metaslab_group_alloc_increment(spa_t *spa, uint64_t vdev, void *tag, int flags)
2166 metaslab_group_t *mg;
2168 if (!(flags & METASLAB_ASYNC_ALLOC) ||
2169 flags & METASLAB_DONT_THROTTLE)
2172 mg = vdev_lookup_top(spa, vdev)->vdev_mg;
2173 if (!mg->mg_class->mc_alloc_throttle_enabled)
2176 (void) refcount_add(&mg->mg_alloc_queue_depth, tag);
2180 metaslab_group_alloc_decrement(spa_t *spa, uint64_t vdev, void *tag, int flags)
2182 metaslab_group_t *mg;
2184 if (!(flags & METASLAB_ASYNC_ALLOC) ||
2185 flags & METASLAB_DONT_THROTTLE)
2188 mg = vdev_lookup_top(spa, vdev)->vdev_mg;
2189 if (!mg->mg_class->mc_alloc_throttle_enabled)
2192 (void) refcount_remove(&mg->mg_alloc_queue_depth, tag);
2196 metaslab_group_alloc_verify(spa_t *spa, const blkptr_t *bp, void *tag)
2199 const dva_t *dva = bp->blk_dva;
2200 int ndvas = BP_GET_NDVAS(bp);
2203 for (d = 0; d < ndvas; d++) {
2204 uint64_t vdev = DVA_GET_VDEV(&dva[d]);
2205 metaslab_group_t *mg = vdev_lookup_top(spa, vdev)->vdev_mg;
2206 VERIFY(refcount_not_held(&mg->mg_alloc_queue_depth, tag));
2212 metaslab_group_alloc(metaslab_group_t *mg, uint64_t asize,
2213 uint64_t txg, uint64_t min_distance, dva_t *dva, int d)
2215 spa_t *spa = mg->mg_vd->vdev_spa;
2216 metaslab_t *msp = NULL;
2217 uint64_t offset = -1ULL;
2218 avl_tree_t *t = &mg->mg_metaslab_tree;
2219 uint64_t activation_weight;
2220 uint64_t target_distance;
2223 activation_weight = METASLAB_WEIGHT_PRIMARY;
2224 for (i = 0; i < d; i++) {
2225 if (DVA_GET_VDEV(&dva[i]) == mg->mg_vd->vdev_id) {
2226 activation_weight = METASLAB_WEIGHT_SECONDARY;
2232 boolean_t was_active;
2234 mutex_enter(&mg->mg_lock);
2235 for (msp = avl_first(t); msp; msp = AVL_NEXT(t, msp)) {
2236 if (msp->ms_weight < asize) {
2237 spa_dbgmsg(spa, "%s: failed to meet weight "
2238 "requirement: vdev %llu, txg %llu, mg %p, "
2239 "msp %p, asize %llu, "
2240 "weight %llu", spa_name(spa),
2241 mg->mg_vd->vdev_id, txg,
2242 mg, msp, asize, msp->ms_weight);
2243 mutex_exit(&mg->mg_lock);
2248 * If the selected metaslab is condensing, skip it.
2250 if (msp->ms_condensing)
2253 was_active = msp->ms_weight & METASLAB_ACTIVE_MASK;
2254 if (activation_weight == METASLAB_WEIGHT_PRIMARY)
2257 target_distance = min_distance +
2258 (space_map_allocated(msp->ms_sm) != 0 ? 0 :
2261 for (i = 0; i < d; i++)
2262 if (metaslab_distance(msp, &dva[i]) <
2268 mutex_exit(&mg->mg_lock);
2272 mutex_enter(&msp->ms_lock);
2275 * Ensure that the metaslab we have selected is still
2276 * capable of handling our request. It's possible that
2277 * another thread may have changed the weight while we
2278 * were blocked on the metaslab lock.
2280 if (msp->ms_weight < asize || (was_active &&
2281 !(msp->ms_weight & METASLAB_ACTIVE_MASK) &&
2282 activation_weight == METASLAB_WEIGHT_PRIMARY)) {
2283 mutex_exit(&msp->ms_lock);
2287 if ((msp->ms_weight & METASLAB_WEIGHT_SECONDARY) &&
2288 activation_weight == METASLAB_WEIGHT_PRIMARY) {
2289 metaslab_passivate(msp,
2290 msp->ms_weight & ~METASLAB_ACTIVE_MASK);
2291 mutex_exit(&msp->ms_lock);
2295 if (metaslab_activate(msp, activation_weight) != 0) {
2296 mutex_exit(&msp->ms_lock);
2301 * If this metaslab is currently condensing then pick again as
2302 * we can't manipulate this metaslab until it's committed
2305 if (msp->ms_condensing) {
2306 mutex_exit(&msp->ms_lock);
2310 if ((offset = metaslab_block_alloc(msp, asize)) != -1ULL)
2313 metaslab_passivate(msp, metaslab_block_maxsize(msp));
2314 mutex_exit(&msp->ms_lock);
2317 if (range_tree_space(msp->ms_alloctree[txg & TXG_MASK]) == 0)
2318 vdev_dirty(mg->mg_vd, VDD_METASLAB, msp, txg);
2320 range_tree_add(msp->ms_alloctree[txg & TXG_MASK], offset, asize);
2321 msp->ms_access_txg = txg + metaslab_unload_delay;
2323 mutex_exit(&msp->ms_lock);
2328 * Allocate a block for the specified i/o.
2331 metaslab_alloc_dva(spa_t *spa, metaslab_class_t *mc, uint64_t psize,
2332 dva_t *dva, int d, dva_t *hintdva, uint64_t txg, int flags)
2334 metaslab_group_t *mg, *fast_mg, *rotor;
2338 int zio_lock = B_FALSE;
2339 boolean_t allocatable;
2343 ASSERT(!DVA_IS_VALID(&dva[d]));
2346 * For testing, make some blocks above a certain size be gang blocks.
2348 if (psize >= metaslab_gang_bang && (ddi_get_lbolt() & 3) == 0)
2349 return (SET_ERROR(ENOSPC));
2352 * Start at the rotor and loop through all mgs until we find something.
2353 * Note that there's no locking on mc_rotor or mc_aliquot because
2354 * nothing actually breaks if we miss a few updates -- we just won't
2355 * allocate quite as evenly. It all balances out over time.
2357 * If we are doing ditto or log blocks, try to spread them across
2358 * consecutive vdevs. If we're forced to reuse a vdev before we've
2359 * allocated all of our ditto blocks, then try and spread them out on
2360 * that vdev as much as possible. If it turns out to not be possible,
2361 * gradually lower our standards until anything becomes acceptable.
2362 * Also, allocating on consecutive vdevs (as opposed to random vdevs)
2363 * gives us hope of containing our fault domains to something we're
2364 * able to reason about. Otherwise, any two top-level vdev failures
2365 * will guarantee the loss of data. With consecutive allocation,
2366 * only two adjacent top-level vdev failures will result in data loss.
2368 * If we are doing gang blocks (hintdva is non-NULL), try to keep
2369 * ourselves on the same vdev as our gang block header. That
2370 * way, we can hope for locality in vdev_cache, plus it makes our
2371 * fault domains something tractable.
2374 vd = vdev_lookup_top(spa, DVA_GET_VDEV(&hintdva[d]));
2377 * It's possible the vdev we're using as the hint no
2378 * longer exists (i.e. removed). Consult the rotor when
2384 if (flags & METASLAB_HINTBP_AVOID &&
2385 mg->mg_next != NULL)
2390 } else if (d != 0) {
2391 vd = vdev_lookup_top(spa, DVA_GET_VDEV(&dva[d - 1]));
2392 mg = vd->vdev_mg->mg_next;
2393 } else if (flags & METASLAB_FASTWRITE) {
2394 mg = fast_mg = mc->mc_rotor;
2397 if (fast_mg->mg_vd->vdev_pending_fastwrite <
2398 mg->mg_vd->vdev_pending_fastwrite)
2400 } while ((fast_mg = fast_mg->mg_next) != mc->mc_rotor);
2407 * If the hint put us into the wrong metaslab class, or into a
2408 * metaslab group that has been passivated, just follow the rotor.
2410 if (mg->mg_class != mc || mg->mg_activation_count <= 0)
2419 ASSERT(mg->mg_activation_count == 1);
2423 * Don't allocate from faulted devices.
2426 spa_config_enter(spa, SCL_ZIO, FTAG, RW_READER);
2427 allocatable = vdev_allocatable(vd);
2428 spa_config_exit(spa, SCL_ZIO, FTAG);
2430 allocatable = vdev_allocatable(vd);
2434 * Determine if the selected metaslab group is eligible
2435 * for allocations. If we're ganging then don't allow
2436 * this metaslab group to skip allocations since that would
2437 * inadvertently return ENOSPC and suspend the pool
2438 * even though space is still available.
2440 if (allocatable && !GANG_ALLOCATION(flags) && !zio_lock) {
2441 allocatable = metaslab_group_allocatable(mg, rotor,
2448 ASSERT(mg->mg_initialized);
2451 * Avoid writing single-copy data to a failing vdev.
2453 if ((vd->vdev_stat.vs_write_errors > 0 ||
2454 vd->vdev_state < VDEV_STATE_HEALTHY) &&
2455 d == 0 && dshift == 3 && vd->vdev_children == 0) {
2460 ASSERT(mg->mg_class == mc);
2462 distance = vd->vdev_asize >> dshift;
2463 if (distance <= (1ULL << vd->vdev_ms_shift))
2468 asize = vdev_psize_to_asize(vd, psize);
2469 ASSERT(P2PHASE(asize, 1ULL << vd->vdev_ashift) == 0);
2471 offset = metaslab_group_alloc(mg, asize, txg, distance, dva, d);
2473 mutex_enter(&mg->mg_lock);
2474 if (offset == -1ULL) {
2475 mg->mg_failed_allocations++;
2476 if (asize == SPA_GANGBLOCKSIZE) {
2478 * This metaslab group was unable to allocate
2479 * the minimum gang block size so it must be
2480 * out of space. We must notify the allocation
2481 * throttle to start skipping allocation
2482 * attempts to this metaslab group until more
2483 * space becomes available.
2485 * Note: this failure cannot be caused by the
2486 * allocation throttle since the allocation
2487 * throttle is only responsible for skipping
2488 * devices and not failing block allocations.
2490 mg->mg_no_free_space = B_TRUE;
2493 mg->mg_allocations++;
2494 mutex_exit(&mg->mg_lock);
2496 if (offset != -1ULL) {
2498 * If we've just selected this metaslab group,
2499 * figure out whether the corresponding vdev is
2500 * over- or under-used relative to the pool,
2501 * and set an allocation bias to even it out.
2503 * Bias is also used to compensate for unequally
2504 * sized vdevs so that space is allocated fairly.
2506 if (mc->mc_aliquot == 0 && metaslab_bias_enabled) {
2507 vdev_stat_t *vs = &vd->vdev_stat;
2508 int64_t vs_free = vs->vs_space - vs->vs_alloc;
2509 int64_t mc_free = mc->mc_space - mc->mc_alloc;
2513 * Calculate how much more or less we should
2514 * try to allocate from this device during
2515 * this iteration around the rotor.
2517 * This basically introduces a zero-centered
2518 * bias towards the devices with the most
2519 * free space, while compensating for vdev
2523 * vdev V1 = 16M/128M
2524 * vdev V2 = 16M/128M
2525 * ratio(V1) = 100% ratio(V2) = 100%
2527 * vdev V1 = 16M/128M
2528 * vdev V2 = 64M/128M
2529 * ratio(V1) = 127% ratio(V2) = 72%
2531 * vdev V1 = 16M/128M
2532 * vdev V2 = 64M/512M
2533 * ratio(V1) = 40% ratio(V2) = 160%
2535 ratio = (vs_free * mc->mc_alloc_groups * 100) /
2537 mg->mg_bias = ((ratio - 100) *
2538 (int64_t)mg->mg_aliquot) / 100;
2539 } else if (!metaslab_bias_enabled) {
2543 if ((flags & METASLAB_FASTWRITE) ||
2544 atomic_add_64_nv(&mc->mc_aliquot, asize) >=
2545 mg->mg_aliquot + mg->mg_bias) {
2546 mc->mc_rotor = mg->mg_next;
2550 DVA_SET_VDEV(&dva[d], vd->vdev_id);
2551 DVA_SET_OFFSET(&dva[d], offset);
2552 DVA_SET_GANG(&dva[d],
2553 ((flags & METASLAB_GANG_HEADER) ? 1 : 0));
2554 DVA_SET_ASIZE(&dva[d], asize);
2556 if (flags & METASLAB_FASTWRITE) {
2557 atomic_add_64(&vd->vdev_pending_fastwrite,
2564 mc->mc_rotor = mg->mg_next;
2566 } while ((mg = mg->mg_next) != rotor);
2570 ASSERT(dshift < 64);
2574 if (!allocatable && !zio_lock) {
2580 bzero(&dva[d], sizeof (dva_t));
2582 return (SET_ERROR(ENOSPC));
2586 * Free the block represented by DVA in the context of the specified
2587 * transaction group.
2590 metaslab_free_dva(spa_t *spa, const dva_t *dva, uint64_t txg, boolean_t now)
2592 uint64_t vdev = DVA_GET_VDEV(dva);
2593 uint64_t offset = DVA_GET_OFFSET(dva);
2594 uint64_t size = DVA_GET_ASIZE(dva);
2598 if (txg > spa_freeze_txg(spa))
2601 if ((vd = vdev_lookup_top(spa, vdev)) == NULL || !DVA_IS_VALID(dva) ||
2602 (offset >> vd->vdev_ms_shift) >= vd->vdev_ms_count) {
2603 zfs_panic_recover("metaslab_free_dva(): bad DVA %llu:%llu:%llu",
2604 (u_longlong_t)vdev, (u_longlong_t)offset,
2605 (u_longlong_t)size);
2609 msp = vd->vdev_ms[offset >> vd->vdev_ms_shift];
2611 if (DVA_GET_GANG(dva))
2612 size = vdev_psize_to_asize(vd, SPA_GANGBLOCKSIZE);
2614 mutex_enter(&msp->ms_lock);
2617 range_tree_remove(msp->ms_alloctree[txg & TXG_MASK],
2620 VERIFY(!msp->ms_condensing);
2621 VERIFY3U(offset, >=, msp->ms_start);
2622 VERIFY3U(offset + size, <=, msp->ms_start + msp->ms_size);
2623 VERIFY3U(range_tree_space(msp->ms_tree) + size, <=,
2625 VERIFY0(P2PHASE(offset, 1ULL << vd->vdev_ashift));
2626 VERIFY0(P2PHASE(size, 1ULL << vd->vdev_ashift));
2627 range_tree_add(msp->ms_tree, offset, size);
2629 if (range_tree_space(msp->ms_freetree[txg & TXG_MASK]) == 0)
2630 vdev_dirty(vd, VDD_METASLAB, msp, txg);
2631 range_tree_add(msp->ms_freetree[txg & TXG_MASK],
2635 mutex_exit(&msp->ms_lock);
2639 * Intent log support: upon opening the pool after a crash, notify the SPA
2640 * of blocks that the intent log has allocated for immediate write, but
2641 * which are still considered free by the SPA because the last transaction
2642 * group didn't commit yet.
2645 metaslab_claim_dva(spa_t *spa, const dva_t *dva, uint64_t txg)
2647 uint64_t vdev = DVA_GET_VDEV(dva);
2648 uint64_t offset = DVA_GET_OFFSET(dva);
2649 uint64_t size = DVA_GET_ASIZE(dva);
2654 ASSERT(DVA_IS_VALID(dva));
2656 if ((vd = vdev_lookup_top(spa, vdev)) == NULL ||
2657 (offset >> vd->vdev_ms_shift) >= vd->vdev_ms_count)
2658 return (SET_ERROR(ENXIO));
2660 msp = vd->vdev_ms[offset >> vd->vdev_ms_shift];
2662 if (DVA_GET_GANG(dva))
2663 size = vdev_psize_to_asize(vd, SPA_GANGBLOCKSIZE);
2665 mutex_enter(&msp->ms_lock);
2667 if ((txg != 0 && spa_writeable(spa)) || !msp->ms_loaded)
2668 error = metaslab_activate(msp, METASLAB_WEIGHT_SECONDARY);
2670 if (error == 0 && !range_tree_contains(msp->ms_tree, offset, size))
2671 error = SET_ERROR(ENOENT);
2673 if (error || txg == 0) { /* txg == 0 indicates dry run */
2674 mutex_exit(&msp->ms_lock);
2678 VERIFY(!msp->ms_condensing);
2679 VERIFY0(P2PHASE(offset, 1ULL << vd->vdev_ashift));
2680 VERIFY0(P2PHASE(size, 1ULL << vd->vdev_ashift));
2681 VERIFY3U(range_tree_space(msp->ms_tree) - size, <=, msp->ms_size);
2682 range_tree_remove(msp->ms_tree, offset, size);
2684 if (spa_writeable(spa)) { /* don't dirty if we're zdb(1M) */
2685 if (range_tree_space(msp->ms_alloctree[txg & TXG_MASK]) == 0)
2686 vdev_dirty(vd, VDD_METASLAB, msp, txg);
2687 range_tree_add(msp->ms_alloctree[txg & TXG_MASK], offset, size);
2690 mutex_exit(&msp->ms_lock);
2696 * Reserve some allocation slots. The reservation system must be called
2697 * before we call into the allocator. If there aren't any available slots
2698 * then the I/O will be throttled until an I/O completes and its slots are
2699 * freed up. The function returns true if it was successful in placing
2703 metaslab_class_throttle_reserve(metaslab_class_t *mc, int slots, zio_t *zio,
2706 uint64_t available_slots = 0;
2707 uint64_t reserved_slots;
2708 boolean_t slot_reserved = B_FALSE;
2710 ASSERT(mc->mc_alloc_throttle_enabled);
2711 mutex_enter(&mc->mc_lock);
2713 reserved_slots = refcount_count(&mc->mc_alloc_slots);
2714 if (reserved_slots < mc->mc_alloc_max_slots)
2715 available_slots = mc->mc_alloc_max_slots - reserved_slots;
2717 if (slots <= available_slots || GANG_ALLOCATION(flags)) {
2721 * We reserve the slots individually so that we can unreserve
2722 * them individually when an I/O completes.
2724 for (d = 0; d < slots; d++) {
2725 reserved_slots = refcount_add(&mc->mc_alloc_slots, zio);
2727 zio->io_flags |= ZIO_FLAG_IO_ALLOCATING;
2728 slot_reserved = B_TRUE;
2731 mutex_exit(&mc->mc_lock);
2732 return (slot_reserved);
2736 metaslab_class_throttle_unreserve(metaslab_class_t *mc, int slots, zio_t *zio)
2740 ASSERT(mc->mc_alloc_throttle_enabled);
2741 mutex_enter(&mc->mc_lock);
2742 for (d = 0; d < slots; d++) {
2743 (void) refcount_remove(&mc->mc_alloc_slots, zio);
2745 mutex_exit(&mc->mc_lock);
2749 metaslab_alloc(spa_t *spa, metaslab_class_t *mc, uint64_t psize, blkptr_t *bp,
2750 int ndvas, uint64_t txg, blkptr_t *hintbp, int flags, zio_t *zio)
2752 dva_t *dva = bp->blk_dva;
2753 dva_t *hintdva = hintbp->blk_dva;
2756 ASSERT(bp->blk_birth == 0);
2757 ASSERT(BP_PHYSICAL_BIRTH(bp) == 0);
2759 spa_config_enter(spa, SCL_ALLOC, FTAG, RW_READER);
2761 if (mc->mc_rotor == NULL) { /* no vdevs in this class */
2762 spa_config_exit(spa, SCL_ALLOC, FTAG);
2763 return (SET_ERROR(ENOSPC));
2766 ASSERT(ndvas > 0 && ndvas <= spa_max_replication(spa));
2767 ASSERT(BP_GET_NDVAS(bp) == 0);
2768 ASSERT(hintbp == NULL || ndvas <= BP_GET_NDVAS(hintbp));
2770 for (d = 0; d < ndvas; d++) {
2771 error = metaslab_alloc_dva(spa, mc, psize, dva, d, hintdva,
2774 for (d--; d >= 0; d--) {
2775 metaslab_free_dva(spa, &dva[d], txg, B_TRUE);
2776 metaslab_group_alloc_decrement(spa,
2777 DVA_GET_VDEV(&dva[d]), zio, flags);
2778 bzero(&dva[d], sizeof (dva_t));
2780 spa_config_exit(spa, SCL_ALLOC, FTAG);
2784 * Update the metaslab group's queue depth
2785 * based on the newly allocated dva.
2787 metaslab_group_alloc_increment(spa,
2788 DVA_GET_VDEV(&dva[d]), zio, flags);
2793 ASSERT(BP_GET_NDVAS(bp) == ndvas);
2795 spa_config_exit(spa, SCL_ALLOC, FTAG);
2797 BP_SET_BIRTH(bp, txg, 0);
2803 metaslab_free(spa_t *spa, const blkptr_t *bp, uint64_t txg, boolean_t now)
2805 const dva_t *dva = bp->blk_dva;
2806 int d, ndvas = BP_GET_NDVAS(bp);
2808 ASSERT(!BP_IS_HOLE(bp));
2809 ASSERT(!now || bp->blk_birth >= spa_syncing_txg(spa));
2811 spa_config_enter(spa, SCL_FREE, FTAG, RW_READER);
2813 for (d = 0; d < ndvas; d++)
2814 metaslab_free_dva(spa, &dva[d], txg, now);
2816 spa_config_exit(spa, SCL_FREE, FTAG);
2820 metaslab_claim(spa_t *spa, const blkptr_t *bp, uint64_t txg)
2822 const dva_t *dva = bp->blk_dva;
2823 int ndvas = BP_GET_NDVAS(bp);
2826 ASSERT(!BP_IS_HOLE(bp));
2830 * First do a dry run to make sure all DVAs are claimable,
2831 * so we don't have to unwind from partial failures below.
2833 if ((error = metaslab_claim(spa, bp, 0)) != 0)
2837 spa_config_enter(spa, SCL_ALLOC, FTAG, RW_READER);
2839 for (d = 0; d < ndvas; d++)
2840 if ((error = metaslab_claim_dva(spa, &dva[d], txg)) != 0)
2843 spa_config_exit(spa, SCL_ALLOC, FTAG);
2845 ASSERT(error == 0 || txg == 0);
2851 metaslab_fastwrite_mark(spa_t *spa, const blkptr_t *bp)
2853 const dva_t *dva = bp->blk_dva;
2854 int ndvas = BP_GET_NDVAS(bp);
2855 uint64_t psize = BP_GET_PSIZE(bp);
2859 ASSERT(!BP_IS_HOLE(bp));
2860 ASSERT(!BP_IS_EMBEDDED(bp));
2863 spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
2865 for (d = 0; d < ndvas; d++) {
2866 if ((vd = vdev_lookup_top(spa, DVA_GET_VDEV(&dva[d]))) == NULL)
2868 atomic_add_64(&vd->vdev_pending_fastwrite, psize);
2871 spa_config_exit(spa, SCL_VDEV, FTAG);
2875 metaslab_fastwrite_unmark(spa_t *spa, const blkptr_t *bp)
2877 const dva_t *dva = bp->blk_dva;
2878 int ndvas = BP_GET_NDVAS(bp);
2879 uint64_t psize = BP_GET_PSIZE(bp);
2883 ASSERT(!BP_IS_HOLE(bp));
2884 ASSERT(!BP_IS_EMBEDDED(bp));
2887 spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
2889 for (d = 0; d < ndvas; d++) {
2890 if ((vd = vdev_lookup_top(spa, DVA_GET_VDEV(&dva[d]))) == NULL)
2892 ASSERT3U(vd->vdev_pending_fastwrite, >=, psize);
2893 atomic_sub_64(&vd->vdev_pending_fastwrite, psize);
2896 spa_config_exit(spa, SCL_VDEV, FTAG);
2900 metaslab_check_free(spa_t *spa, const blkptr_t *bp)
2904 if ((zfs_flags & ZFS_DEBUG_ZIO_FREE) == 0)
2907 spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
2908 for (i = 0; i < BP_GET_NDVAS(bp); i++) {
2909 uint64_t vdev = DVA_GET_VDEV(&bp->blk_dva[i]);
2910 vdev_t *vd = vdev_lookup_top(spa, vdev);
2911 uint64_t offset = DVA_GET_OFFSET(&bp->blk_dva[i]);
2912 uint64_t size = DVA_GET_ASIZE(&bp->blk_dva[i]);
2913 metaslab_t *msp = vd->vdev_ms[offset >> vd->vdev_ms_shift];
2916 range_tree_verify(msp->ms_tree, offset, size);
2918 for (j = 0; j < TXG_SIZE; j++)
2919 range_tree_verify(msp->ms_freetree[j], offset, size);
2920 for (j = 0; j < TXG_DEFER_SIZE; j++)
2921 range_tree_verify(msp->ms_defertree[j], offset, size);
2923 spa_config_exit(spa, SCL_VDEV, FTAG);
2926 #if defined(_KERNEL) && defined(HAVE_SPL)
2927 module_param(metaslab_aliquot, ulong, 0644);
2928 module_param(metaslab_debug_load, int, 0644);
2929 module_param(metaslab_debug_unload, int, 0644);
2930 module_param(metaslab_preload_enabled, int, 0644);
2931 module_param(zfs_mg_noalloc_threshold, int, 0644);
2932 module_param(zfs_mg_fragmentation_threshold, int, 0644);
2933 module_param(zfs_metaslab_fragmentation_threshold, int, 0644);
2934 module_param(metaslab_fragmentation_factor_enabled, int, 0644);
2935 module_param(metaslab_lba_weighting_enabled, int, 0644);
2936 module_param(metaslab_bias_enabled, int, 0644);
2938 MODULE_PARM_DESC(metaslab_aliquot,
2939 "allocation granularity (a.k.a. stripe size)");
2940 MODULE_PARM_DESC(metaslab_debug_load,
2941 "load all metaslabs when pool is first opened");
2942 MODULE_PARM_DESC(metaslab_debug_unload,
2943 "prevent metaslabs from being unloaded");
2944 MODULE_PARM_DESC(metaslab_preload_enabled,
2945 "preload potential metaslabs during reassessment");
2947 MODULE_PARM_DESC(zfs_mg_noalloc_threshold,
2948 "percentage of free space for metaslab group to allow allocation");
2949 MODULE_PARM_DESC(zfs_mg_fragmentation_threshold,
2950 "fragmentation for metaslab group to allow allocation");
2952 MODULE_PARM_DESC(zfs_metaslab_fragmentation_threshold,
2953 "fragmentation for metaslab to allow allocation");
2954 MODULE_PARM_DESC(metaslab_fragmentation_factor_enabled,
2955 "use the fragmentation metric to prefer less fragmented metaslabs");
2956 MODULE_PARM_DESC(metaslab_lba_weighting_enabled,
2957 "prefer metaslabs with lower LBAs");
2958 MODULE_PARM_DESC(metaslab_bias_enabled,
2959 "enable metaslab group biasing");
2960 #endif /* _KERNEL && HAVE_SPL */