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15 * If applicable, add the following below this CDDL HEADER, with the
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22 * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
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27 * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
30 #ifndef _SYS_METASLAB_IMPL_H
31 #define _SYS_METASLAB_IMPL_H
33 #include <sys/metaslab.h>
34 #include <sys/space_map.h>
35 #include <sys/range_tree.h>
44 struct metaslab_class {
46 metaslab_group_t *mc_rotor;
47 metaslab_ops_t *mc_ops;
49 uint64_t mc_alloc_groups; /* # of allocatable groups */
50 uint64_t mc_alloc; /* total allocated space */
51 uint64_t mc_deferred; /* total deferred frees */
52 uint64_t mc_space; /* total space (alloc + free) */
53 uint64_t mc_dspace; /* total deflated space */
54 uint64_t mc_minblocksize;
57 struct metaslab_group {
59 avl_tree_t mg_metaslab_tree;
61 boolean_t mg_allocatable; /* can we allocate? */
62 uint64_t mg_free_capacity; /* percentage free */
64 int64_t mg_activation_count;
65 metaslab_class_t *mg_class;
68 metaslab_group_t *mg_prev;
69 metaslab_group_t *mg_next;
73 * This value defines the number of elements in the ms_lbas array. The value
74 * of 64 was chosen as it covers to cover all power of 2 buckets up to
75 * UINT64_MAX. This is the equivalent of highbit(UINT64_MAX).
80 * Each metaslab maintains a set of in-core trees to track metaslab operations.
81 * The in-core free tree (ms_tree) contains the current list of free segments.
82 * As blocks are allocated, the allocated segment are removed from the ms_tree
83 * and added to a per txg allocation tree (ms_alloctree). As blocks are freed,
84 * they are added to the per txg free tree (ms_freetree). These per txg
85 * trees allow us to process all allocations and frees in syncing context
86 * where it is safe to update the on-disk space maps. One additional in-core
87 * tree is maintained to track deferred frees (ms_defertree). Once a block
88 * is freed it will move from the ms_freetree to the ms_defertree. A deferred
89 * free means that a block has been freed but cannot be used by the pool
90 * until TXG_DEFER_SIZE transactions groups later. For example, a block
91 * that is freed in txg 50 will not be available for reallocation until
92 * txg 52 (50 + TXG_DEFER_SIZE). This provides a safety net for uberblock
93 * rollback. A pool could be safely rolled back TXG_DEFERS_SIZE
94 * transactions groups and ensure that no block has been reallocated.
96 * The simplified transition diagram looks like this:
102 * free segment (ms_tree) --------> ms_alloctree ----> (write to space map)
105 * | ms_freetree <--- FREE
109 * +----------- ms_defertree <-------+---------> (write to space map)
112 * Each metaslab's space is tracked in a single space map in the MOS,
113 * which is only updated in syncing context. Each time we sync a txg,
114 * we append the allocs and frees from that txg to the space map.
115 * The pool space is only updated once all metaslabs have finished syncing.
117 * To load the in-core free tree we read the space map from disk.
118 * This object contains a series of alloc and free records that are
119 * combined to make up the list of all free segments in this metaslab. These
120 * segments are represented in-core by the ms_tree and are stored in an
123 * As the space map grows (as a result of the appends) it will
124 * eventually become space-inefficient. When the metaslab's in-core free tree
125 * is zfs_condense_pct/100 times the size of the minimal on-disk
126 * representation, we rewrite it in its minimized form. If a metaslab
127 * needs to condense then we must set the ms_condensing flag to ensure
128 * that allocations are not performed on the metaslab that is being written.
132 kcondvar_t ms_load_cv;
134 metaslab_ops_t *ms_ops;
139 range_tree_t *ms_alloctree[TXG_SIZE];
140 range_tree_t *ms_freetree[TXG_SIZE];
141 range_tree_t *ms_defertree[TXG_DEFER_SIZE];
142 range_tree_t *ms_tree;
144 boolean_t ms_condensing; /* condensing? */
146 boolean_t ms_loading;
148 int64_t ms_deferspace; /* sum of ms_defermap[] space */
149 uint64_t ms_weight; /* weight vs. others in group */
151 uint64_t ms_access_txg;
154 * The metaslab block allocators can optionally use a size-ordered
155 * range tree and/or an array of LBAs. Not all allocators use
156 * this functionality. The ms_size_tree should always contain the
157 * same number of segments as the ms_tree. The only difference
158 * is that the ms_size_tree is ordered by segment sizes.
160 avl_tree_t ms_size_tree;
161 uint64_t ms_lbas[MAX_LBAS];
163 metaslab_group_t *ms_group; /* metaslab group */
164 avl_node_t ms_group_node; /* node in metaslab group tree */
165 txg_node_t ms_txg_node; /* per-txg dirty metaslab links */
172 #endif /* _SYS_METASLAB_IMPL_H */