/* * CDDL HEADER START * * The contents of this file are subject to the terms of the * Common Development and Distribution License (the "License"). * You may not use this file except in compliance with the License. * * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE * or http://www.opensolaris.org/os/licensing. * See the License for the specific language governing permissions * and limitations under the License. * * When distributing Covered Code, include this CDDL HEADER in each * file and include the License file at usr/src/OPENSOLARIS.LICENSE. * If applicable, add the following below this CDDL HEADER, with the * fields enclosed by brackets "[]" replaced with your own identifying * information: Portions Copyright [yyyy] [name of copyright owner] * * CDDL HEADER END */ /* * Copyright 2009 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. */ /* * Copyright (c) 2011, 2015 by Delphix. All rights reserved. */ #ifndef _SYS_METASLAB_IMPL_H #define _SYS_METASLAB_IMPL_H #include #include #include #include #include #include #ifdef __cplusplus extern "C" { #endif /* * A metaslab class encompasses a category of allocatable top-level vdevs. * Each top-level vdev is associated with a metaslab group which defines * the allocatable region for that vdev. Examples of these categories include * "normal" for data block allocations (i.e. main pool allocations) or "log" * for allocations designated for intent log devices (i.e. slog devices). * When a block allocation is requested from the SPA it is associated with a * metaslab_class_t, and only top-level vdevs (i.e. metaslab groups) belonging * to the class can be used to satisfy that request. Allocations are done * by traversing the metaslab groups that are linked off of the mc_rotor field. * This rotor points to the next metaslab group where allocations will be * attempted. Allocating a block is a 3 step process -- select the metaslab * group, select the metaslab, and then allocate the block. The metaslab * class defines the low-level block allocator that will be used as the * final step in allocation. These allocators are pluggable allowing each class * to use a block allocator that best suits that class. */ struct metaslab_class { kmutex_t mc_lock; spa_t *mc_spa; metaslab_group_t *mc_rotor; metaslab_ops_t *mc_ops; uint64_t mc_aliquot; /* * Track the number of metaslab groups that have been initialized * and can accept allocations. An initialized metaslab group is * one has been completely added to the config (i.e. we have * updated the MOS config and the space has been added to the pool). */ uint64_t mc_groups; /* * Toggle to enable/disable the allocation throttle. */ boolean_t mc_alloc_throttle_enabled; /* * The allocation throttle works on a reservation system. Whenever * an asynchronous zio wants to perform an allocation it must * first reserve the number of blocks that it wants to allocate. * If there aren't sufficient slots available for the pending zio * then that I/O is throttled until more slots free up. The current * number of reserved allocations is maintained by the mc_alloc_slots * refcount. The mc_alloc_max_slots value determines the maximum * number of allocations that the system allows. Gang blocks are * allowed to reserve slots even if we've reached the maximum * number of allocations allowed. */ uint64_t mc_alloc_max_slots; refcount_t mc_alloc_slots; uint64_t mc_alloc_groups; /* # of allocatable groups */ uint64_t mc_alloc; /* total allocated space */ uint64_t mc_deferred; /* total deferred frees */ uint64_t mc_space; /* total space (alloc + free) */ uint64_t mc_dspace; /* total deflated space */ uint64_t mc_histogram[RANGE_TREE_HISTOGRAM_SIZE]; }; /* * Metaslab groups encapsulate all the allocatable regions (i.e. metaslabs) * of a top-level vdev. They are linked togther to form a circular linked * list and can belong to only one metaslab class. Metaslab groups may become * ineligible for allocations for a number of reasons such as limited free * space, fragmentation, or going offline. When this happens the allocator will * simply find the next metaslab group in the linked list and attempt * to allocate from that group instead. */ struct metaslab_group { kmutex_t mg_lock; avl_tree_t mg_metaslab_tree; uint64_t mg_aliquot; boolean_t mg_allocatable; /* can we allocate? */ /* * A metaslab group is considered to be initialized only after * we have updated the MOS config and added the space to the pool. * We only allow allocation attempts to a metaslab group if it * has been initialized. */ boolean_t mg_initialized; uint64_t mg_free_capacity; /* percentage free */ int64_t mg_bias; int64_t mg_activation_count; metaslab_class_t *mg_class; vdev_t *mg_vd; taskq_t *mg_taskq; metaslab_group_t *mg_prev; metaslab_group_t *mg_next; /* * Each metaslab group can handle mg_max_alloc_queue_depth allocations * which are tracked by mg_alloc_queue_depth. It's possible for a * metaslab group to handle more allocations than its max. This * can occur when gang blocks are required or when other groups * are unable to handle their share of allocations. */ uint64_t mg_max_alloc_queue_depth; refcount_t mg_alloc_queue_depth; /* * A metalab group that can no longer allocate the minimum block * size will set mg_no_free_space. Once a metaslab group is out * of space then its share of work must be distributed to other * groups. */ boolean_t mg_no_free_space; uint64_t mg_allocations; uint64_t mg_failed_allocations; uint64_t mg_fragmentation; uint64_t mg_histogram[RANGE_TREE_HISTOGRAM_SIZE]; }; /* * This value defines the number of elements in the ms_lbas array. The value * of 64 was chosen as it covers all power of 2 buckets up to UINT64_MAX. * This is the equivalent of highbit(UINT64_MAX). */ #define MAX_LBAS 64 /* * Each metaslab maintains a set of in-core trees to track metaslab operations. * The in-core free tree (ms_tree) contains the current list of free segments. * As blocks are allocated, the allocated segment are removed from the ms_tree * and added to a per txg allocation tree (ms_alloctree). As blocks are freed, * they are added to the per txg free tree (ms_freetree). These per txg * trees allow us to process all allocations and frees in syncing context * where it is safe to update the on-disk space maps. One additional in-core * tree is maintained to track deferred frees (ms_defertree). Once a block * is freed it will move from the ms_freetree to the ms_defertree. A deferred * free means that a block has been freed but cannot be used by the pool * until TXG_DEFER_SIZE transactions groups later. For example, a block * that is freed in txg 50 will not be available for reallocation until * txg 52 (50 + TXG_DEFER_SIZE). This provides a safety net for uberblock * rollback. A pool could be safely rolled back TXG_DEFERS_SIZE * transactions groups and ensure that no block has been reallocated. * * The simplified transition diagram looks like this: * * * ALLOCATE * | * V * free segment (ms_tree) --------> ms_alloctree ----> (write to space map) * ^ * | * | ms_freetree <--- FREE * | | * | | * | | * +----------- ms_defertree <-------+---------> (write to space map) * * * Each metaslab's space is tracked in a single space map in the MOS, * which is only updated in syncing context. Each time we sync a txg, * we append the allocs and frees from that txg to the space map. * The pool space is only updated once all metaslabs have finished syncing. * * To load the in-core free tree we read the space map from disk. * This object contains a series of alloc and free records that are * combined to make up the list of all free segments in this metaslab. These * segments are represented in-core by the ms_tree and are stored in an * AVL tree. * * As the space map grows (as a result of the appends) it will * eventually become space-inefficient. When the metaslab's in-core free tree * is zfs_condense_pct/100 times the size of the minimal on-disk * representation, we rewrite it in its minimized form. If a metaslab * needs to condense then we must set the ms_condensing flag to ensure * that allocations are not performed on the metaslab that is being written. */ struct metaslab { kmutex_t ms_lock; kcondvar_t ms_load_cv; space_map_t *ms_sm; metaslab_ops_t *ms_ops; uint64_t ms_id; uint64_t ms_start; uint64_t ms_size; uint64_t ms_fragmentation; range_tree_t *ms_alloctree[TXG_SIZE]; range_tree_t *ms_freetree[TXG_SIZE]; range_tree_t *ms_defertree[TXG_DEFER_SIZE]; range_tree_t *ms_tree; boolean_t ms_condensing; /* condensing? */ boolean_t ms_condense_wanted; boolean_t ms_loaded; boolean_t ms_loading; int64_t ms_deferspace; /* sum of ms_defermap[] space */ uint64_t ms_weight; /* weight vs. others in group */ uint64_t ms_access_txg; /* * The metaslab block allocators can optionally use a size-ordered * range tree and/or an array of LBAs. Not all allocators use * this functionality. The ms_size_tree should always contain the * same number of segments as the ms_tree. The only difference * is that the ms_size_tree is ordered by segment sizes. */ avl_tree_t ms_size_tree; uint64_t ms_lbas[MAX_LBAS]; metaslab_group_t *ms_group; /* metaslab group */ avl_node_t ms_group_node; /* node in metaslab group tree */ txg_node_t ms_txg_node; /* per-txg dirty metaslab links */ }; #ifdef __cplusplus } #endif #endif /* _SYS_METASLAB_IMPL_H */