metaslab_impl.h revision 269773
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, 2014 by Delphix. All rights reserved. 28 */ 29 30#ifndef _SYS_METASLAB_IMPL_H 31#define _SYS_METASLAB_IMPL_H 32 33#include <sys/metaslab.h> 34#include <sys/space_map.h> 35#include <sys/range_tree.h> 36#include <sys/vdev.h> 37#include <sys/txg.h> 38#include <sys/avl.h> 39 40#ifdef __cplusplus 41extern "C" { 42#endif 43 44/* 45 * A metaslab class encompasses a category of allocatable top-level vdevs. 46 * Each top-level vdev is associated with a metaslab group which defines 47 * the allocatable region for that vdev. Examples of these categories include 48 * "normal" for data block allocations (i.e. main pool allocations) or "log" 49 * for allocations designated for intent log devices (i.e. slog devices). 50 * When a block allocation is requested from the SPA it is associated with a 51 * metaslab_class_t, and only top-level vdevs (i.e. metaslab groups) belonging 52 * to the class can be used to satisfy that request. Allocations are done 53 * by traversing the metaslab groups that are linked off of the mc_rotor field. 54 * This rotor points to the next metaslab group where allocations will be 55 * attempted. Allocating a block is a 3 step process -- select the metaslab 56 * group, select the metaslab, and then allocate the block. The metaslab 57 * class defines the low-level block allocator that will be used as the 58 * final step in allocation. These allocators are pluggable allowing each class 59 * to use a block allocator that best suits that class. 60 */ 61struct metaslab_class { 62 spa_t *mc_spa; 63 metaslab_group_t *mc_rotor; 64 metaslab_ops_t *mc_ops; 65 uint64_t mc_aliquot; 66 uint64_t mc_alloc_groups; /* # of allocatable groups */ 67 uint64_t mc_alloc; /* total allocated space */ 68 uint64_t mc_deferred; /* total deferred frees */ 69 uint64_t mc_space; /* total space (alloc + free) */ 70 uint64_t mc_dspace; /* total deflated space */ 71 uint64_t mc_minblocksize; 72 uint64_t mc_histogram[RANGE_TREE_HISTOGRAM_SIZE]; 73}; 74 75/* 76 * Metaslab groups encapsulate all the allocatable regions (i.e. metaslabs) 77 * of a top-level vdev. They are linked togther to form a circular linked 78 * list and can belong to only one metaslab class. Metaslab groups may become 79 * ineligible for allocations for a number of reasons such as limited free 80 * space, fragmentation, or going offline. When this happens the allocator will 81 * simply find the next metaslab group in the linked list and attempt 82 * to allocate from that group instead. 83 */ 84struct metaslab_group { 85 kmutex_t mg_lock; 86 avl_tree_t mg_metaslab_tree; 87 uint64_t mg_aliquot; 88 boolean_t mg_allocatable; /* can we allocate? */ 89 uint64_t mg_free_capacity; /* percentage free */ 90 int64_t mg_bias; 91 int64_t mg_activation_count; 92 metaslab_class_t *mg_class; 93 vdev_t *mg_vd; 94 taskq_t *mg_taskq; 95 metaslab_group_t *mg_prev; 96 metaslab_group_t *mg_next; 97 uint64_t mg_fragmentation; 98 uint64_t mg_histogram[RANGE_TREE_HISTOGRAM_SIZE]; 99}; 100 101/* 102 * This value defines the number of elements in the ms_lbas array. The value 103 * of 64 was chosen as it covers all power of 2 buckets up to UINT64_MAX. 104 * This is the equivalent of highbit(UINT64_MAX). 105 */ 106#define MAX_LBAS 64 107 108/* 109 * Each metaslab maintains a set of in-core trees to track metaslab operations. 110 * The in-core free tree (ms_tree) contains the current list of free segments. 111 * As blocks are allocated, the allocated segment are removed from the ms_tree 112 * and added to a per txg allocation tree (ms_alloctree). As blocks are freed, 113 * they are added to the per txg free tree (ms_freetree). These per txg 114 * trees allow us to process all allocations and frees in syncing context 115 * where it is safe to update the on-disk space maps. One additional in-core 116 * tree is maintained to track deferred frees (ms_defertree). Once a block 117 * is freed it will move from the ms_freetree to the ms_defertree. A deferred 118 * free means that a block has been freed but cannot be used by the pool 119 * until TXG_DEFER_SIZE transactions groups later. For example, a block 120 * that is freed in txg 50 will not be available for reallocation until 121 * txg 52 (50 + TXG_DEFER_SIZE). This provides a safety net for uberblock 122 * rollback. A pool could be safely rolled back TXG_DEFERS_SIZE 123 * transactions groups and ensure that no block has been reallocated. 124 * 125 * The simplified transition diagram looks like this: 126 * 127 * 128 * ALLOCATE 129 * | 130 * V 131 * free segment (ms_tree) --------> ms_alloctree ----> (write to space map) 132 * ^ 133 * | 134 * | ms_freetree <--- FREE 135 * | | 136 * | | 137 * | | 138 * +----------- ms_defertree <-------+---------> (write to space map) 139 * 140 * 141 * Each metaslab's space is tracked in a single space map in the MOS, 142 * which is only updated in syncing context. Each time we sync a txg, 143 * we append the allocs and frees from that txg to the space map. 144 * The pool space is only updated once all metaslabs have finished syncing. 145 * 146 * To load the in-core free tree we read the space map from disk. 147 * This object contains a series of alloc and free records that are 148 * combined to make up the list of all free segments in this metaslab. These 149 * segments are represented in-core by the ms_tree and are stored in an 150 * AVL tree. 151 * 152 * As the space map grows (as a result of the appends) it will 153 * eventually become space-inefficient. When the metaslab's in-core free tree 154 * is zfs_condense_pct/100 times the size of the minimal on-disk 155 * representation, we rewrite it in its minimized form. If a metaslab 156 * needs to condense then we must set the ms_condensing flag to ensure 157 * that allocations are not performed on the metaslab that is being written. 158 */ 159struct metaslab { 160 kmutex_t ms_lock; 161 kcondvar_t ms_load_cv; 162 space_map_t *ms_sm; 163 metaslab_ops_t *ms_ops; 164 uint64_t ms_id; 165 uint64_t ms_start; 166 uint64_t ms_size; 167 uint64_t ms_fragmentation; 168 169 range_tree_t *ms_alloctree[TXG_SIZE]; 170 range_tree_t *ms_freetree[TXG_SIZE]; 171 range_tree_t *ms_defertree[TXG_DEFER_SIZE]; 172 range_tree_t *ms_tree; 173 174 boolean_t ms_condensing; /* condensing? */ 175 boolean_t ms_condense_wanted; 176 boolean_t ms_loaded; 177 boolean_t ms_loading; 178 179 int64_t ms_deferspace; /* sum of ms_defermap[] space */ 180 uint64_t ms_weight; /* weight vs. others in group */ 181 uint64_t ms_access_txg; 182 183 /* 184 * The metaslab block allocators can optionally use a size-ordered 185 * range tree and/or an array of LBAs. Not all allocators use 186 * this functionality. The ms_size_tree should always contain the 187 * same number of segments as the ms_tree. The only difference 188 * is that the ms_size_tree is ordered by segment sizes. 189 */ 190 avl_tree_t ms_size_tree; 191 uint64_t ms_lbas[MAX_LBAS]; 192 193 metaslab_group_t *ms_group; /* metaslab group */ 194 avl_node_t ms_group_node; /* node in metaslab group tree */ 195 txg_node_t ms_txg_node; /* per-txg dirty metaslab links */ 196}; 197 198#ifdef __cplusplus 199} 200#endif 201 202#endif /* _SYS_METASLAB_IMPL_H */ 203