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4e21fd060a
This change introduces a new weighting algorithm to improve metaslab selection. The new weighting algorithm relies on the SPACEMAP_HISTOGRAM feature. As a result, the metaslab weight now encodes the type of weighting algorithm used (size-based vs segment-based). Porting Notes: The metaslab allocation tracing code is conditionally removed on linux (dependent on mdb debugger). Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Chris Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Pavel Zakharov pavel.zakharov@delphix.com Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Don Brady <don.brady@intel.com> OpenZFS-issue: https://www.illumos.org/issues/7303 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/d5190931bd Closes #5404
365 lines
14 KiB
C
365 lines
14 KiB
C
/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License (the "License").
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* You may not use this file except in compliance with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or http://www.opensolaris.org/os/licensing.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright 2009 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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/*
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* Copyright (c) 2011, 2016 by Delphix. All rights reserved.
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*/
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#ifndef _SYS_METASLAB_IMPL_H
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#define _SYS_METASLAB_IMPL_H
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#include <sys/metaslab.h>
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#include <sys/space_map.h>
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#include <sys/range_tree.h>
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#include <sys/vdev.h>
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#include <sys/txg.h>
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#include <sys/avl.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*
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* Metaslab allocation tracing record.
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*/
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typedef struct metaslab_alloc_trace {
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list_node_t mat_list_node;
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metaslab_group_t *mat_mg;
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metaslab_t *mat_msp;
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uint64_t mat_size;
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uint64_t mat_weight;
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uint32_t mat_dva_id;
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uint64_t mat_offset;
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} metaslab_alloc_trace_t;
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/*
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* Used by the metaslab allocation tracing facility to indicate
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* error conditions. These errors are stored to the offset member
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* of the metaslab_alloc_trace_t record and displayed by mdb.
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*/
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typedef enum trace_alloc_type {
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TRACE_ALLOC_FAILURE = -1ULL,
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TRACE_TOO_SMALL = -2ULL,
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TRACE_FORCE_GANG = -3ULL,
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TRACE_NOT_ALLOCATABLE = -4ULL,
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TRACE_GROUP_FAILURE = -5ULL,
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TRACE_ENOSPC = -6ULL,
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TRACE_CONDENSING = -7ULL,
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TRACE_VDEV_ERROR = -8ULL
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} trace_alloc_type_t;
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#define METASLAB_WEIGHT_PRIMARY (1ULL << 63)
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#define METASLAB_WEIGHT_SECONDARY (1ULL << 62)
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#define METASLAB_WEIGHT_TYPE (1ULL << 61)
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#define METASLAB_ACTIVE_MASK \
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(METASLAB_WEIGHT_PRIMARY | METASLAB_WEIGHT_SECONDARY)
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/*
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* The metaslab weight is used to encode the amount of free space in a
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* metaslab, such that the "best" metaslab appears first when sorting the
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* metaslabs by weight. The weight (and therefore the "best" metaslab) can
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* be determined in two different ways: by computing a weighted sum of all
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* the free space in the metaslab (a space based weight) or by counting only
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* the free segments of the largest size (a segment based weight). We prefer
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* the segment based weight because it reflects how the free space is
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* comprised, but we cannot always use it -- legacy pools do not have the
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* space map histogram information necessary to determine the largest
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* contiguous regions. Pools that have the space map histogram determine
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* the segment weight by looking at each bucket in the histogram and
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* determining the free space whose size in bytes is in the range:
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* [2^i, 2^(i+1))
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* We then encode the largest index, i, that contains regions into the
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* segment-weighted value.
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*
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* Space-based weight:
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*
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* 64 56 48 40 32 24 16 8 0
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* +-------+-------+-------+-------+-------+-------+-------+-------+
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* |PS1| weighted-free space |
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* +-------+-------+-------+-------+-------+-------+-------+-------+
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*
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* PS - indicates primary and secondary activation
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* space - the fragmentation-weighted space
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*
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* Segment-based weight:
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*
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* 64 56 48 40 32 24 16 8 0
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* +-------+-------+-------+-------+-------+-------+-------+-------+
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* |PS0| idx| count of segments in region |
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* +-------+-------+-------+-------+-------+-------+-------+-------+
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*
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* PS - indicates primary and secondary activation
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* idx - index for the highest bucket in the histogram
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* count - number of segments in the specified bucket
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*/
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#define WEIGHT_GET_ACTIVE(weight) BF64_GET((weight), 62, 2)
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#define WEIGHT_SET_ACTIVE(weight, x) BF64_SET((weight), 62, 2, x)
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#define WEIGHT_IS_SPACEBASED(weight) \
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((weight) == 0 || BF64_GET((weight), 61, 1))
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#define WEIGHT_SET_SPACEBASED(weight) BF64_SET((weight), 61, 1, 1)
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/*
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* These macros are only applicable to segment-based weighting.
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*/
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#define WEIGHT_GET_INDEX(weight) BF64_GET((weight), 55, 6)
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#define WEIGHT_SET_INDEX(weight, x) BF64_SET((weight), 55, 6, x)
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#define WEIGHT_GET_COUNT(weight) BF64_GET((weight), 0, 55)
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#define WEIGHT_SET_COUNT(weight, x) BF64_SET((weight), 0, 55, x)
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/*
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* A metaslab class encompasses a category of allocatable top-level vdevs.
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* Each top-level vdev is associated with a metaslab group which defines
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* the allocatable region for that vdev. Examples of these categories include
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* "normal" for data block allocations (i.e. main pool allocations) or "log"
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* for allocations designated for intent log devices (i.e. slog devices).
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* When a block allocation is requested from the SPA it is associated with a
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* metaslab_class_t, and only top-level vdevs (i.e. metaslab groups) belonging
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* to the class can be used to satisfy that request. Allocations are done
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* by traversing the metaslab groups that are linked off of the mc_rotor field.
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* This rotor points to the next metaslab group where allocations will be
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* attempted. Allocating a block is a 3 step process -- select the metaslab
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* group, select the metaslab, and then allocate the block. The metaslab
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* class defines the low-level block allocator that will be used as the
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* final step in allocation. These allocators are pluggable allowing each class
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* to use a block allocator that best suits that class.
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*/
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struct metaslab_class {
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kmutex_t mc_lock;
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spa_t *mc_spa;
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metaslab_group_t *mc_rotor;
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metaslab_ops_t *mc_ops;
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uint64_t mc_aliquot;
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/*
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* Track the number of metaslab groups that have been initialized
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* and can accept allocations. An initialized metaslab group is
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* one has been completely added to the config (i.e. we have
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* updated the MOS config and the space has been added to the pool).
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*/
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uint64_t mc_groups;
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/*
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* Toggle to enable/disable the allocation throttle.
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*/
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boolean_t mc_alloc_throttle_enabled;
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/*
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* The allocation throttle works on a reservation system. Whenever
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* an asynchronous zio wants to perform an allocation it must
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* first reserve the number of blocks that it wants to allocate.
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* If there aren't sufficient slots available for the pending zio
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* then that I/O is throttled until more slots free up. The current
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* number of reserved allocations is maintained by the mc_alloc_slots
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* refcount. The mc_alloc_max_slots value determines the maximum
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* number of allocations that the system allows. Gang blocks are
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* allowed to reserve slots even if we've reached the maximum
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* number of allocations allowed.
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*/
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uint64_t mc_alloc_max_slots;
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refcount_t mc_alloc_slots;
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uint64_t mc_alloc_groups; /* # of allocatable groups */
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uint64_t mc_alloc; /* total allocated space */
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uint64_t mc_deferred; /* total deferred frees */
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uint64_t mc_space; /* total space (alloc + free) */
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uint64_t mc_dspace; /* total deflated space */
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uint64_t mc_histogram[RANGE_TREE_HISTOGRAM_SIZE];
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};
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/*
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* Metaslab groups encapsulate all the allocatable regions (i.e. metaslabs)
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* of a top-level vdev. They are linked together to form a circular linked
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* list and can belong to only one metaslab class. Metaslab groups may become
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* ineligible for allocations for a number of reasons such as limited free
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* space, fragmentation, or going offline. When this happens the allocator will
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* simply find the next metaslab group in the linked list and attempt
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* to allocate from that group instead.
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*/
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struct metaslab_group {
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kmutex_t mg_lock;
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avl_tree_t mg_metaslab_tree;
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uint64_t mg_aliquot;
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boolean_t mg_allocatable; /* can we allocate? */
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/*
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* A metaslab group is considered to be initialized only after
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* we have updated the MOS config and added the space to the pool.
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* We only allow allocation attempts to a metaslab group if it
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* has been initialized.
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*/
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boolean_t mg_initialized;
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uint64_t mg_free_capacity; /* percentage free */
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int64_t mg_bias;
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int64_t mg_activation_count;
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metaslab_class_t *mg_class;
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vdev_t *mg_vd;
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taskq_t *mg_taskq;
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metaslab_group_t *mg_prev;
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metaslab_group_t *mg_next;
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/*
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* Each metaslab group can handle mg_max_alloc_queue_depth allocations
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* which are tracked by mg_alloc_queue_depth. It's possible for a
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* metaslab group to handle more allocations than its max. This
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* can occur when gang blocks are required or when other groups
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* are unable to handle their share of allocations.
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*/
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uint64_t mg_max_alloc_queue_depth;
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refcount_t mg_alloc_queue_depth;
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/*
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* A metalab group that can no longer allocate the minimum block
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* size will set mg_no_free_space. Once a metaslab group is out
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* of space then its share of work must be distributed to other
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* groups.
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*/
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boolean_t mg_no_free_space;
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uint64_t mg_allocations;
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uint64_t mg_failed_allocations;
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uint64_t mg_fragmentation;
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uint64_t mg_histogram[RANGE_TREE_HISTOGRAM_SIZE];
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};
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/*
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* This value defines the number of elements in the ms_lbas array. The value
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* of 64 was chosen as it covers all power of 2 buckets up to UINT64_MAX.
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* This is the equivalent of highbit(UINT64_MAX).
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*/
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#define MAX_LBAS 64
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/*
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* Each metaslab maintains a set of in-core trees to track metaslab operations.
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* The in-core free tree (ms_tree) contains the current list of free segments.
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* As blocks are allocated, the allocated segment are removed from the ms_tree
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* and added to a per txg allocation tree (ms_alloctree). As blocks are freed,
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* they are added to the per txg free tree (ms_freetree). These per txg
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* trees allow us to process all allocations and frees in syncing context
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* where it is safe to update the on-disk space maps. One additional in-core
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* tree is maintained to track deferred frees (ms_defertree). Once a block
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* is freed it will move from the ms_freetree to the ms_defertree. A deferred
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* free means that a block has been freed but cannot be used by the pool
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* until TXG_DEFER_SIZE transactions groups later. For example, a block
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* that is freed in txg 50 will not be available for reallocation until
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* txg 52 (50 + TXG_DEFER_SIZE). This provides a safety net for uberblock
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* rollback. A pool could be safely rolled back TXG_DEFERS_SIZE
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* transactions groups and ensure that no block has been reallocated.
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*
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* The simplified transition diagram looks like this:
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*
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*
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* ALLOCATE
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* |
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* V
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* free segment (ms_tree) --------> ms_alloctree ----> (write to space map)
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* ^
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* |
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* | ms_freetree <--- FREE
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* | |
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* | |
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* | |
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* +----------- ms_defertree <-------+---------> (write to space map)
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*
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*
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* Each metaslab's space is tracked in a single space map in the MOS,
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* which is only updated in syncing context. Each time we sync a txg,
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* we append the allocs and frees from that txg to the space map.
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* The pool space is only updated once all metaslabs have finished syncing.
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*
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* To load the in-core free tree we read the space map from disk.
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* This object contains a series of alloc and free records that are
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* combined to make up the list of all free segments in this metaslab. These
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* segments are represented in-core by the ms_tree and are stored in an
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* AVL tree.
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*
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* As the space map grows (as a result of the appends) it will
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* eventually become space-inefficient. When the metaslab's in-core free tree
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* is zfs_condense_pct/100 times the size of the minimal on-disk
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* representation, we rewrite it in its minimized form. If a metaslab
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* needs to condense then we must set the ms_condensing flag to ensure
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* that allocations are not performed on the metaslab that is being written.
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*/
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struct metaslab {
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kmutex_t ms_lock;
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kcondvar_t ms_load_cv;
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space_map_t *ms_sm;
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uint64_t ms_id;
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uint64_t ms_start;
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uint64_t ms_size;
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uint64_t ms_fragmentation;
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range_tree_t *ms_alloctree[TXG_SIZE];
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range_tree_t *ms_freetree[TXG_SIZE];
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range_tree_t *ms_defertree[TXG_DEFER_SIZE];
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range_tree_t *ms_tree;
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boolean_t ms_condensing; /* condensing? */
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boolean_t ms_condense_wanted;
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/*
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* We must hold both ms_lock and ms_group->mg_lock in order to
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* modify ms_loaded.
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*/
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boolean_t ms_loaded;
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boolean_t ms_loading;
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int64_t ms_deferspace; /* sum of ms_defermap[] space */
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uint64_t ms_weight; /* weight vs. others in group */
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uint64_t ms_activation_weight; /* activation weight */
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/*
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* Track of whenever a metaslab is selected for loading or allocation.
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* We use this value to determine how long the metaslab should
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* stay cached.
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*/
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uint64_t ms_selected_txg;
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uint64_t ms_alloc_txg; /* last successful alloc (debug only) */
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uint64_t ms_max_size; /* maximum allocatable size */
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/*
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* The metaslab block allocators can optionally use a size-ordered
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* range tree and/or an array of LBAs. Not all allocators use
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* this functionality. The ms_size_tree should always contain the
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* same number of segments as the ms_tree. The only difference
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* is that the ms_size_tree is ordered by segment sizes.
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*/
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avl_tree_t ms_size_tree;
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uint64_t ms_lbas[MAX_LBAS];
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metaslab_group_t *ms_group; /* metaslab group */
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avl_node_t ms_group_node; /* node in metaslab group tree */
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txg_node_t ms_txg_node; /* per-txg dirty metaslab links */
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};
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#ifdef __cplusplus
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}
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#endif
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#endif /* _SYS_METASLAB_IMPL_H */
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