Reduce loaded range tree memory usage

This patch implements a new tree structure for ZFS, and uses it to 
store range trees more efficiently.

The new structure is approximately a B-tree, though there are some 
small differences from the usual characterizations. The tree has core 
nodes and leaf nodes; each contain data elements, which the elements 
in the core nodes acting as separators between its children. The 
difference between core and leaf nodes is that the core nodes have an 
array of children, while leaf nodes don't. Every node in the tree may 
be only partially full; in most cases, they are all at least 50% full 
(in terms of element count) except for the root node, which can be 
less full. Underfull nodes will steal from their neighbors or merge to 
remain full enough, while overfull nodes will split in two. The data 
elements are contained in tree-controlled buffers; they are copied 
into these on insertion, and overwritten on deletion. This means that 
the elements are not independently allocated, which reduces overhead, 
but also means they can't be shared between trees (and also that 
pointers to them are only valid until a side-effectful tree operation 
occurs). The overhead varies based on how dense the tree is, but is 
usually on the order of about 50% of the element size; the per-node 
overheads are very small, and so don't make a significant difference. 
The trees can accept arbitrary records; they accept a size and a 
comparator to allow them to be used for a variety of purposes.

The new trees replace the AVL trees used in the range trees today. 
Currently, the range_seg_t structure contains three 8 byte integers 
of payload and two 24 byte avl_tree_node_ts to handle its storage in 
both an offset-sorted tree and a size-sorted tree (total size: 64 
bytes). In the new model, the range seg structures are usually two 4 
byte integers, but a separate one needs to exist for the size-sorted 
and offset-sorted tree. Between the raw size, the 50% overhead, and 
the double storage, the new btrees are expected to use 8*1.5*2 = 24 
bytes per record, or 33.3% as much memory as the AVL trees (this is 
for the purposes of storing metaslab range trees; for other purposes, 
like scrubs, they use ~50% as much memory).

We reduced the size of the payload in the range segments by teaching 
range trees about starting offsets and shifts; since metaslabs have a 
fixed starting offset, and they all operate in terms of disk sectors, 
we can store the ranges using 4-byte integers as long as the size of 
the metaslab divided by the sector size is less than 2^32. For 512-byte
sectors, this is a 2^41 (or 2TB) metaslab, which with the default
settings corresponds to a 256PB disk. 4k sector disks can handle 
metaslabs up to 2^46 bytes, or 2^63 byte disks. Since we do not 
anticipate disks of this size in the near future, there should be 
almost no cases where metaslabs need 64-byte integers to store their 
ranges. We do still have the capability to store 64-byte integer ranges 
to account for cases where we are storing per-vdev (or per-dnode) trees, 
which could reasonably go above the limits discussed. We also do not 
store fill information in the compact version of the node, since it 
is only used for sorted scrub.

We also optimized the metaslab loading process in various other ways
to offset some inefficiencies in the btree model. While individual
operations (find, insert, remove_from) are faster for the btree than 
they are for the avl tree, remove usually requires a find operation, 
while in the AVL tree model the element itself suffices. Some clever 
changes actually caused an overall speedup in metaslab loading; we use 
approximately 40% less cpu to load metaslabs in our tests on Illumos.

Another memory and performance optimization was achieved by changing 
what is stored in the size-sorted trees. When a disk is heavily 
fragmented, the df algorithm used by default in ZFS will almost always 
find a number of small regions in its initial cursor-based search; it 
will usually only fall back to the size-sorted tree to find larger 
regions. If we increase the size of the cursor-based search slightly, 
and don't store segments that are smaller than a tunable size floor 
in the size-sorted tree, we can further cut memory usage down to 
below 20% of what the AVL trees store. This also results in further 
reductions in CPU time spent loading metaslabs.

The 16KiB size floor was chosen because it results in substantial memory 
usage reduction while not usually resulting in situations where we can't 
find an appropriate chunk with the cursor and are forced to use an 
oversized chunk from the size-sorted tree. In addition, even if we do 
have to use an oversized chunk from the size-sorted tree, the chunk 
would be too small to use for ZIL allocations, so it isn't as big of a 
loss as it might otherwise be. And often, more small allocations will 
follow the initial one, and the cursor search will now find the 
remainder of the chunk we didn't use all of and use it for subsequent 
allocations. Practical testing has shown little or no change in 
fragmentation as a result of this change.

If the size-sorted tree becomes empty while the offset sorted one still 
has entries, it will load all the entries from the offset sorted tree 
and disregard the size floor until it is unloaded again. This operation 
occurs rarely with the default setting, only on incredibly thoroughly 
fragmented pools.

There are some other small changes to zdb to teach it to handle btrees, 
but nothing major.
                                           
Reviewed-by: George Wilson <[email protected]>
Reviewed-by: Matt Ahrens <[email protected]>
Reviewed by: Sebastien Roy [email protected]
Reviewed-by: Igor Kozhukhov <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Paul Dagnelie <[email protected]>
Closes #9181 

11 files changed, 564 insertions, 82 deletions

diff --git a/include/sys/Makefile.am b/include/sys/Makefile.am
index 734d5c161..5785bfd55 100644
--- a/include/sys/Makefile.am
+++ b/include/sys/Makefile.am
@@ -7,10 +7,12 @@ COMMON_H = \
 	$(top_srcdir)/include/sys/arc_impl.h \
 	$(top_srcdir)/include/sys/avl.h \
 	$(top_srcdir)/include/sys/avl_impl.h \
+	$(top_srcdir)/include/sys/bitops.h \
 	$(top_srcdir)/include/sys/blkptr.h \
 	$(top_srcdir)/include/sys/bplist.h \
 	$(top_srcdir)/include/sys/bpobj.h \
 	$(top_srcdir)/include/sys/bptree.h \
+	$(top_srcdir)/include/sys/btree.h \
 	$(top_srcdir)/include/sys/bqueue.h \
 	$(top_srcdir)/include/sys/cityhash.h \
 	$(top_srcdir)/include/sys/dataset_kstats.h \
diff --git a/include/sys/avl.h b/include/sys/avl.h
index 962e8b1cf..6c4e7ed5c 100644
--- a/include/sys/avl.h
+++ b/include/sys/avl.h
@@ -108,9 +108,9 @@ extern "C" {
 /*
  * AVL comparator helpers
  */
-#define	AVL_ISIGN(a)	(((a) > 0) - ((a) < 0))
-#define	AVL_CMP(a, b)	(((a) > (b)) - ((a) < (b)))
-#define	AVL_PCMP(a, b)	\
+#define	TREE_ISIGN(a)	(((a) > 0) - ((a) < 0))
+#define	TREE_CMP(a, b)	(((a) > (b)) - ((a) < (b)))
+#define	TREE_PCMP(a, b)	\
 	(((uintptr_t)(a) > (uintptr_t)(b)) - ((uintptr_t)(a) < (uintptr_t)(b)))
 
 /*
diff --git a/include/sys/bitops.h b/include/sys/bitops.h
new file mode 100644
index 000000000..56d52073b
--- /dev/null
+++ b/include/sys/bitops.h
@@ -0,0 +1,90 @@
+/*
+ * 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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 2019 by Delphix. All rights reserved.
+ * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
+ * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
+ * Copyright 2013 Saso Kiselkov. All rights reserved.
+ * Copyright (c) 2014 Integros [integros.com]
+ * Copyright 2017 Joyent, Inc.
+ * Copyright (c) 2017 Datto Inc.
+ */
+
+#ifndef _SYS_BITOPS_H
+#define	_SYS_BITOPS_H
+
+#include <sys/zfs_context.h>
+
+#ifdef	__cplusplus
+extern "C" {
+#endif
+
+/*
+ * General-purpose 32-bit and 64-bit bitfield encodings.
+ */
+#define	BF32_DECODE(x, low, len)	P2PHASE((x) >> (low), 1U << (len))
+#define	BF64_DECODE(x, low, len)	P2PHASE((x) >> (low), 1ULL << (len))
+#define	BF32_ENCODE(x, low, len)	(P2PHASE((x), 1U << (len)) << (low))
+#define	BF64_ENCODE(x, low, len)	(P2PHASE((x), 1ULL << (len)) << (low))
+
+#define	BF32_GET(x, low, len)		BF32_DECODE(x, low, len)
+#define	BF64_GET(x, low, len)		BF64_DECODE(x, low, len)
+
+#define	BF32_SET(x, low, len, val) do { \
+	ASSERT3U(val, <, 1U << (len)); \
+	ASSERT3U(low + len, <=, 32); \
+	(x) ^= BF32_ENCODE((x >> low) ^ (val), low, len); \
+_NOTE(CONSTCOND) } while (0)
+
+#define	BF64_SET(x, low, len, val) do { \
+	ASSERT3U(val, <, 1ULL << (len)); \
+	ASSERT3U(low + len, <=, 64); \
+	((x) ^= BF64_ENCODE((x >> low) ^ (val), low, len)); \
+_NOTE(CONSTCOND) } while (0)
+
+#define	BF32_GET_SB(x, low, len, shift, bias)	\
+	((BF32_GET(x, low, len) + (bias)) << (shift))
+#define	BF64_GET_SB(x, low, len, shift, bias)	\
+	((BF64_GET(x, low, len) + (bias)) << (shift))
+
+/*
+ * We use ASSERT3U instead of ASSERT in these macros to prevent a lint error in
+ * the case where val is a constant.  We can't fix ASSERT because it's used as
+ * an expression in several places in the kernel; as a result, changing it to
+ * the do{} while() syntax to allow us to _NOTE the CONSTCOND is not an option.
+ */
+#define	BF32_SET_SB(x, low, len, shift, bias, val) do { \
+	ASSERT3U(IS_P2ALIGNED(val, 1U << shift), !=, B_FALSE); \
+	ASSERT3S((val) >> (shift), >=, bias); \
+	BF32_SET(x, low, len, ((val) >> (shift)) - (bias)); \
+_NOTE(CONSTCOND) } while (0)
+#define	BF64_SET_SB(x, low, len, shift, bias, val) do { \
+	ASSERT3U(IS_P2ALIGNED(val, 1ULL << shift), !=, B_FALSE); \
+	ASSERT3S((val) >> (shift), >=, bias); \
+	BF64_SET(x, low, len, ((val) >> (shift)) - (bias)); \
+_NOTE(CONSTCOND) } while (0)
+
+#ifdef	__cplusplus
+}
+#endif
+
+#endif /* _SYS_BITOPS_H */
diff --git a/include/sys/btree.h b/include/sys/btree.h
new file mode 100644
index 000000000..1673b5217
--- /dev/null
+++ b/include/sys/btree.h
@@ -0,0 +1,238 @@
+/*
+ * CDDL HEADER START
+ *
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright (c) 2019 by Delphix. All rights reserved.
+ */
+
+#ifndef	_BTREE_H
+#define	_BTREE_H
+
+#ifdef	__cplusplus
+extern "C" {
+#endif
+
+#include	<sys/zfs_context.h>
+
+/*
+ * This file defines the interface for a B-Tree implementation for ZFS. The
+ * tree can be used to store arbitrary sortable data types with low overhead
+ * and good operation performance. In addition the tree intelligently
+ * optimizes bulk in-order insertions to improve memory use and performance.
+ *
+ * Note that for all B-Tree functions, the values returned are pointers to the
+ * internal copies of the data in the tree. The internal data can only be
+ * safely mutated if the changes cannot change the ordering of the element
+ * with respect to any other elements in the tree.
+ *
+ * The major drawback of the B-Tree is that any returned elements or indexes
+ * are only valid until a side-effectful operation occurs, since these can
+ * result in reallocation or relocation of data. Side effectful operations are
+ * defined as insertion, removal, and zfs_btree_destroy_nodes.
+ *
+ * The B-Tree has two types of nodes: core nodes, and leaf nodes. Core
+ * nodes have an array of children pointing to other nodes, and an array of
+ * elements that act as separators between the elements of the subtrees rooted
+ * at its children. Leaf nodes only contain data elements, and form the bottom
+ * layer of the tree. Unlike B+ Trees, in this B-Tree implementation the
+ * elements in the core nodes are not copies of or references to leaf node
+ * elements.  Each element occcurs only once in the tree, no matter what kind
+ * of node it is in.
+ *
+ * The tree's height is the same throughout, unlike many other forms of search
+ * tree. Each node (except for the root) must be between half minus one and
+ * completely full of elements (and children) at all times. Any operation that
+ * would put the node outside of that range results in a rebalancing operation
+ * (taking, merging, or splitting).
+ *
+ * This tree was implemented using descriptions from Wikipedia's articles on
+ * B-Trees and B+ Trees.
+ */
+
+/*
+ * Decreasing these values results in smaller memmove operations, but more of
+ * them, and increased memory overhead. Increasing these values results in
+ * higher variance in operation time, and reduces memory overhead.
+ */
+#define	BTREE_CORE_ELEMS	128
+#define	BTREE_LEAF_SIZE		4096
+
+extern kmem_cache_t *zfs_btree_leaf_cache;
+
+typedef struct zfs_btree_hdr {
+	struct zfs_btree_core	*bth_parent;
+	boolean_t		bth_core;
+	/*
+	 * For both leaf and core nodes, represents the number of elements in
+	 * the node. For core nodes, they will have bth_count + 1 children.
+	 */
+	uint32_t		bth_count;
+} zfs_btree_hdr_t;
+
+typedef struct zfs_btree_core {
+	zfs_btree_hdr_t	btc_hdr;
+	zfs_btree_hdr_t	*btc_children[BTREE_CORE_ELEMS + 1];
+	uint8_t		btc_elems[];
+} zfs_btree_core_t;
+
+typedef struct zfs_btree_leaf {
+	zfs_btree_hdr_t	btl_hdr;
+	uint8_t		btl_elems[];
+} zfs_btree_leaf_t;
+
+typedef struct zfs_btree_index {
+	zfs_btree_hdr_t	*bti_node;
+	uint64_t	bti_offset;
+	/*
+	 * True if the location is before the list offset, false if it's at
+	 * the listed offset.
+	 */
+	boolean_t	bti_before;
+} zfs_btree_index_t;
+
+typedef struct btree {
+	zfs_btree_hdr_t		*bt_root;
+	int64_t			bt_height;
+	size_t			bt_elem_size;
+	uint64_t		bt_num_elems;
+	uint64_t		bt_num_nodes;
+	zfs_btree_leaf_t	*bt_bulk; // non-null if bulk loading
+	int (*bt_compar) (const void *, const void *);
+} zfs_btree_t;
+
+/*
+ * Allocate and deallocate caches for btree nodes.
+ */
+void zfs_btree_init(void);
+void zfs_btree_fini(void);
+
+/*
+ * Initialize an B-Tree. Arguments are:
+ *
+ * tree   - the tree to be initialized
+ * compar - function to compare two nodes, it must return exactly: -1, 0, or +1
+ *          -1 for <, 0 for ==, and +1 for >
+ * size   - the value of sizeof(struct my_type)
+ */
+void zfs_btree_create(zfs_btree_t *, int (*) (const void *, const void *),
+    size_t);
+
+/*
+ * Find a node with a matching value in the tree. Returns the matching node
+ * found. If not found, it returns NULL and then if "where" is not NULL it sets
+ * "where" for use with zfs_btree_insert() or zfs_btree_nearest().
+ *
+ * node   - node that has the value being looked for
+ * where  - position for use with zfs_btree_nearest() or zfs_btree_insert(),
+ *          may be NULL
+ */
+void *zfs_btree_find(zfs_btree_t *, const void *, zfs_btree_index_t *);
+
+/*
+ * Insert a node into the tree.
+ *
+ * node   - the node to insert
+ * where  - position as returned from zfs_btree_find()
+ */
+void zfs_btree_insert(zfs_btree_t *, const void *, const zfs_btree_index_t *);
+
+/*
+ * Return the first or last valued node in the tree. Will return NULL
+ * if the tree is empty.
+ */
+void *zfs_btree_first(zfs_btree_t *, zfs_btree_index_t *);
+void *zfs_btree_last(zfs_btree_t *, zfs_btree_index_t *);
+
+/*
+ * Return the next or previous valued node in the tree.
+ */
+void *zfs_btree_next(zfs_btree_t *, const zfs_btree_index_t *,
+    zfs_btree_index_t *);
+void *zfs_btree_prev(zfs_btree_t *, const zfs_btree_index_t *,
+    zfs_btree_index_t *);
+
+/*
+ * Get a value from a tree and an index.
+ */
+void *zfs_btree_get(zfs_btree_t *, zfs_btree_index_t *);
+
+/*
+ * Add a single value to the tree. The value must not compare equal to any
+ * other node already in the tree.
+ */
+void zfs_btree_add(zfs_btree_t *, const void *);
+
+/*
+ * Remove a single value from the tree.  The value must be in the tree. The
+ * pointer passed in may be a pointer into a tree-controlled buffer, but it
+ * need not be.
+ */
+void zfs_btree_remove(zfs_btree_t *, const void *);
+
+/*
+ * Remove the value at the given location from the tree.
+ */
+void zfs_btree_remove_from(zfs_btree_t *, zfs_btree_index_t *);
+
+/*
+ * Return the number of nodes in the tree
+ */
+ulong_t zfs_btree_numnodes(zfs_btree_t *);
+
+/*
+ * Used to destroy any remaining nodes in a tree. The cookie argument should
+ * be initialized to NULL before the first call. Returns a node that has been
+ * removed from the tree and may be free()'d. Returns NULL when the tree is
+ * empty.
+ *
+ * Once you call zfs_btree_destroy_nodes(), you can only continuing calling it
+ * and finally zfs_btree_destroy(). No other B-Tree routines will be valid.
+ *
+ * cookie - an index used to save state between calls to
+ * zfs_btree_destroy_nodes()
+ *
+ * EXAMPLE:
+ *	zfs_btree_t *tree;
+ *	struct my_data *node;
+ *	zfs_btree_index_t *cookie;
+ *
+ *	cookie = NULL;
+ *	while ((node = zfs_btree_destroy_nodes(tree, &cookie)) != NULL)
+ *		data_destroy(node);
+ *	zfs_btree_destroy(tree);
+ */
+void *zfs_btree_destroy_nodes(zfs_btree_t *, zfs_btree_index_t **);
+
+/*
+ * Destroys all nodes in the tree quickly. This doesn't give the caller an
+ * opportunity to iterate over each node and do its own cleanup; for that, use
+ * zfs_btree_destroy_nodes().
+ */
+void zfs_btree_clear(zfs_btree_t *);
+
+/*
+ * Final destroy of an B-Tree. Arguments are:
+ *
+ * tree   - the empty tree to destroy
+ */
+void zfs_btree_destroy(zfs_btree_t *tree);
+
+/* Runs a variety of self-checks on the btree to verify integrity. */
+void zfs_btree_verify(zfs_btree_t *tree);
+
+#ifdef	__cplusplus
+}
+#endif
+
+#endif	/* _BTREE_H */
diff --git a/include/sys/metaslab.h b/include/sys/metaslab.h
index 00b8b4758..f8d9c6a82 100644
--- a/include/sys/metaslab.h
+++ b/include/sys/metaslab.h
@@ -95,8 +95,8 @@ void metaslab_check_free(spa_t *, const blkptr_t *);
 void metaslab_fastwrite_mark(spa_t *, const blkptr_t *);
 void metaslab_fastwrite_unmark(spa_t *, const blkptr_t *);
 
-void metaslab_alloc_trace_init(void);
-void metaslab_alloc_trace_fini(void);
+void metaslab_stat_init(void);
+void metaslab_stat_fini(void);
 void metaslab_trace_init(zio_alloc_list_t *);
 void metaslab_trace_fini(zio_alloc_list_t *);
 
diff --git a/include/sys/metaslab_impl.h b/include/sys/metaslab_impl.h
index 3ce39183e..d140f741d 100644
--- a/include/sys/metaslab_impl.h
+++ b/include/sys/metaslab_impl.h
@@ -509,8 +509,8 @@ struct metaslab {
 	 * only difference is that the ms_allocatable_by_size is ordered by
 	 * segment sizes.
 	 */
-	avl_tree_t	ms_allocatable_by_size;
-	avl_tree_t	ms_unflushed_frees_by_size;
+	zfs_btree_t		ms_allocatable_by_size;
+	zfs_btree_t		ms_unflushed_frees_by_size;
 	uint64_t	ms_lbas[MAX_LBAS];
 
 	metaslab_group_t *ms_group;	/* metaslab group		*/
diff --git a/include/sys/range_tree.h b/include/sys/range_tree.h
index e299613b8..d80faa933 100644
--- a/include/sys/range_tree.h
+++ b/include/sys/range_tree.h
@@ -30,7 +30,7 @@
 #ifndef _SYS_RANGE_TREE_H
 #define	_SYS_RANGE_TREE_H
 
-#include <sys/avl.h>
+#include <sys/btree.h>
 #include <sys/dmu.h>
 
 #ifdef	__cplusplus
@@ -41,20 +41,35 @@ extern "C" {
 
 typedef struct range_tree_ops range_tree_ops_t;
 
+typedef enum range_seg_type {
+	RANGE_SEG32,
+	RANGE_SEG64,
+	RANGE_SEG_GAP,
+	RANGE_SEG_NUM_TYPES,
+} range_seg_type_t;
+
 /*
  * Note: the range_tree may not be accessed concurrently; consumers
  * must provide external locking if required.
  */
 typedef struct range_tree {
-	avl_tree_t	rt_root;	/* offset-ordered segment AVL tree */
+	zfs_btree_t	rt_root;	/* offset-ordered segment b-tree */
 	uint64_t	rt_space;	/* sum of all segments in the map */
-	uint64_t	rt_gap;		/* allowable inter-segment gap */
+	range_seg_type_t rt_type;	/* type of range_seg_t in use */
+	/*
+	 * All data that is stored in the range tree must have a start higher
+	 * than or equal to rt_start, and all sizes and offsets must be
+	 * multiples of 1 << rt_shift.
+	 */
+	uint8_t		rt_shift;
+	uint64_t	rt_start;
 	range_tree_ops_t *rt_ops;
 
-	/* rt_avl_compare should only be set if rt_arg is an AVL tree */
+	/* rt_btree_compare should only be set if rt_arg is a b-tree */
 	void		*rt_arg;
-	int (*rt_avl_compare)(const void *, const void *);
+	int (*rt_btree_compare)(const void *, const void *);
 
+	uint64_t	rt_gap;		/* allowable inter-segment gap */
 
 	/*
 	 * The rt_histogram maintains a histogram of ranges. Each bucket,
@@ -64,36 +79,217 @@ typedef struct range_tree {
 	uint64_t	rt_histogram[RANGE_TREE_HISTOGRAM_SIZE];
 } range_tree_t;
 
-typedef struct range_seg {
-	avl_node_t	rs_node;	/* AVL node */
-	avl_node_t	rs_pp_node;	/* AVL picker-private node */
+typedef struct range_seg32 {
+	uint32_t	rs_start;	/* starting offset of this segment */
+	uint32_t	rs_end;		/* ending offset (non-inclusive) */
+} range_seg32_t;
+
+/*
+ * Extremely large metaslabs, vdev-wide trees, and dnode-wide trees may
+ * require 64-bit integers for ranges.
+ */
+typedef struct range_seg64 {
+	uint64_t	rs_start;	/* starting offset of this segment */
+	uint64_t	rs_end;		/* ending offset (non-inclusive) */
+} range_seg64_t;
+
+typedef struct range_seg_gap {
 	uint64_t	rs_start;	/* starting offset of this segment */
 	uint64_t	rs_end;		/* ending offset (non-inclusive) */
 	uint64_t	rs_fill;	/* actual fill if gap mode is on */
-} range_seg_t;
+} range_seg_gap_t;
+
+/*
+ * This type needs to be the largest of the range segs, since it will be stack
+ * allocated and then cast the actual type to do tree operations.
+ */
+typedef range_seg_gap_t range_seg_max_t;
+
+/*
+ * This is just for clarity of code purposes, so we can make it clear that a
+ * pointer is to a range seg of some type; when we need to do the actual math,
+ * we'll figure out the real type.
+ */
+typedef void range_seg_t;
 
 struct range_tree_ops {
 	void    (*rtop_create)(range_tree_t *rt, void *arg);
 	void    (*rtop_destroy)(range_tree_t *rt, void *arg);
-	void	(*rtop_add)(range_tree_t *rt, range_seg_t *rs, void *arg);
-	void    (*rtop_remove)(range_tree_t *rt, range_seg_t *rs, void *arg);
+	void	(*rtop_add)(range_tree_t *rt, void *rs, void *arg);
+	void    (*rtop_remove)(range_tree_t *rt, void *rs, void *arg);
 	void	(*rtop_vacate)(range_tree_t *rt, void *arg);
 };
 
+static inline uint64_t
+rs_get_start_raw(const range_seg_t *rs, const range_tree_t *rt)
+{
+	ASSERT3U(rt->rt_type, <=, RANGE_SEG_NUM_TYPES);
+	switch (rt->rt_type) {
+	case RANGE_SEG32:
+		return (((range_seg32_t *)rs)->rs_start);
+	case RANGE_SEG64:
+		return (((range_seg64_t *)rs)->rs_start);
+	case RANGE_SEG_GAP:
+		return (((range_seg_gap_t *)rs)->rs_start);
+	default:
+		VERIFY(0);
+		return (0);
+	}
+}
+
+static inline uint64_t
+rs_get_end_raw(const range_seg_t *rs, const range_tree_t *rt)
+{
+	ASSERT3U(rt->rt_type, <=, RANGE_SEG_NUM_TYPES);
+	switch (rt->rt_type) {
+	case RANGE_SEG32:
+		return (((range_seg32_t *)rs)->rs_end);
+	case RANGE_SEG64:
+		return (((range_seg64_t *)rs)->rs_end);
+	case RANGE_SEG_GAP:
+		return (((range_seg_gap_t *)rs)->rs_end);
+	default:
+		VERIFY(0);
+		return (0);
+	}
+}
+
+static inline uint64_t
+rs_get_fill_raw(const range_seg_t *rs, const range_tree_t *rt)
+{
+	ASSERT3U(rt->rt_type, <=, RANGE_SEG_NUM_TYPES);
+	switch (rt->rt_type) {
+	case RANGE_SEG32: {
+		const range_seg32_t *r32 = rs;
+		return (r32->rs_end - r32->rs_start);
+	}
+	case RANGE_SEG64: {
+		const range_seg64_t *r64 = rs;
+		return (r64->rs_end - r64->rs_start);
+	}
+	case RANGE_SEG_GAP:
+		return (((range_seg_gap_t *)rs)->rs_fill);
+	default:
+		VERIFY(0);
+		return (0);
+	}
+
+}
+
+static inline uint64_t
+rs_get_start(const range_seg_t *rs, const range_tree_t *rt)
+{
+	return ((rs_get_start_raw(rs, rt) << rt->rt_shift) + rt->rt_start);
+}
+
+static inline uint64_t
+rs_get_end(const range_seg_t *rs, const range_tree_t *rt)
+{
+	return ((rs_get_end_raw(rs, rt) << rt->rt_shift) + rt->rt_start);
+}
+
+static inline uint64_t
+rs_get_fill(const range_seg_t *rs, const range_tree_t *rt)
+{
+	return (rs_get_fill_raw(rs, rt) << rt->rt_shift);
+}
+
+static inline void
+rs_set_start_raw(range_seg_t *rs, range_tree_t *rt, uint64_t start)
+{
+	ASSERT3U(rt->rt_type, <=, RANGE_SEG_NUM_TYPES);
+	switch (rt->rt_type) {
+	case RANGE_SEG32:
+		ASSERT3U(start, <=, UINT32_MAX);
+		((range_seg32_t *)rs)->rs_start = (uint32_t)start;
+		break;
+	case RANGE_SEG64:
+		((range_seg64_t *)rs)->rs_start = start;
+		break;
+	case RANGE_SEG_GAP:
+		((range_seg_gap_t *)rs)->rs_start = start;
+		break;
+	default:
+		VERIFY(0);
+	}
+}
+
+static inline void
+rs_set_end_raw(range_seg_t *rs, range_tree_t *rt, uint64_t end)
+{
+	ASSERT3U(rt->rt_type, <=, RANGE_SEG_NUM_TYPES);
+	switch (rt->rt_type) {
+	case RANGE_SEG32:
+		ASSERT3U(end, <=, UINT32_MAX);
+		((range_seg32_t *)rs)->rs_end = (uint32_t)end;
+		break;
+	case RANGE_SEG64:
+		((range_seg64_t *)rs)->rs_end = end;
+		break;
+	case RANGE_SEG_GAP:
+		((range_seg_gap_t *)rs)->rs_end = end;
+		break;
+	default:
+		VERIFY(0);
+	}
+}
+
+static inline void
+rs_set_fill_raw(range_seg_t *rs, range_tree_t *rt, uint64_t fill)
+{
+	ASSERT3U(rt->rt_type, <=, RANGE_SEG_NUM_TYPES);
+	switch (rt->rt_type) {
+	case RANGE_SEG32:
+		/* fall through */
+	case RANGE_SEG64:
+		ASSERT3U(fill, ==, rs_get_end_raw(rs, rt) - rs_get_start_raw(rs,
+		    rt));
+		break;
+	case RANGE_SEG_GAP:
+		((range_seg_gap_t *)rs)->rs_fill = fill;
+		break;
+	default:
+		VERIFY(0);
+	}
+}
+
+static inline void
+rs_set_start(range_seg_t *rs, range_tree_t *rt, uint64_t start)
+{
+	ASSERT3U(start, >=, rt->rt_start);
+	ASSERT(IS_P2ALIGNED(start, 1ULL << rt->rt_shift));
+	rs_set_start_raw(rs, rt, (start - rt->rt_start) >> rt->rt_shift);
+}
+
+static inline void
+rs_set_end(range_seg_t *rs, range_tree_t *rt, uint64_t end)
+{
+	ASSERT3U(end, >=, rt->rt_start);
+	ASSERT(IS_P2ALIGNED(end, 1ULL << rt->rt_shift));
+	rs_set_end_raw(rs, rt, (end - rt->rt_start) >> rt->rt_shift);
+}
+
+static inline void
+rs_set_fill(range_seg_t *rs, range_tree_t *rt, uint64_t fill)
+{
+	ASSERT(IS_P2ALIGNED(fill, 1ULL << rt->rt_shift));
+	rs_set_fill_raw(rs, rt, fill >> rt->rt_shift);
+}
+
 typedef void range_tree_func_t(void *arg, uint64_t start, uint64_t size);
 
-void range_tree_init(void);
-void range_tree_fini(void);
-range_tree_t *range_tree_create_impl(range_tree_ops_t *ops, void *arg,
-    int (*avl_compare) (const void *, const void *), uint64_t gap);
-range_tree_t *range_tree_create(range_tree_ops_t *ops, void *arg);
+range_tree_t *range_tree_create_impl(range_tree_ops_t *ops,
+    range_seg_type_t type, void *arg, uint64_t start, uint64_t shift,
+    int (*zfs_btree_compare) (const void *, const void *), uint64_t gap);
+range_tree_t *range_tree_create(range_tree_ops_t *ops, range_seg_type_t type,
+    void *arg, uint64_t start, uint64_t shift);
 void range_tree_destroy(range_tree_t *rt);
 boolean_t range_tree_contains(range_tree_t *rt, uint64_t start, uint64_t size);
+range_seg_t *range_tree_find(range_tree_t *rt, uint64_t start, uint64_t size);
 boolean_t range_tree_find_in(range_tree_t *rt, uint64_t start, uint64_t size,
     uint64_t *ostart, uint64_t *osize);
 void range_tree_verify_not_present(range_tree_t *rt,
     uint64_t start, uint64_t size);
-range_seg_t *range_tree_find(range_tree_t *rt, uint64_t start, uint64_t size);
 void range_tree_resize_segment(range_tree_t *rt, range_seg_t *rs,
     uint64_t newstart, uint64_t newsize);
 uint64_t range_tree_space(range_tree_t *rt);
@@ -120,12 +316,12 @@ void range_tree_remove_xor_add_segment(uint64_t start, uint64_t end,
 void range_tree_remove_xor_add(range_tree_t *rt, range_tree_t *removefrom,
     range_tree_t *addto);
 
-void rt_avl_create(range_tree_t *rt, void *arg);
-void rt_avl_destroy(range_tree_t *rt, void *arg);
-void rt_avl_add(range_tree_t *rt, range_seg_t *rs, void *arg);
-void rt_avl_remove(range_tree_t *rt, range_seg_t *rs, void *arg);
-void rt_avl_vacate(range_tree_t *rt, void *arg);
-extern struct range_tree_ops rt_avl_ops;
+void rt_btree_create(range_tree_t *rt, void *arg);
+void rt_btree_destroy(range_tree_t *rt, void *arg);
+void rt_btree_add(range_tree_t *rt, range_seg_t *rs, void *arg);
+void rt_btree_remove(range_tree_t *rt, range_seg_t *rs, void *arg);
+void rt_btree_vacate(range_tree_t *rt, void *arg);
+extern range_tree_ops_t rt_btree_ops;
 
 #ifdef	__cplusplus
 }
diff --git a/include/sys/spa.h b/include/sys/spa.h
index caa2157b9..18933e0d4 100644
--- a/include/sys/spa.h
+++ b/include/sys/spa.h
@@ -43,6 +43,7 @@
 #include <sys/spa_checksum.h>
 #include <sys/dmu.h>
 #include <sys/space_map.h>
+#include <sys/bitops.h>
 
 #ifdef	__cplusplus
 extern "C" {
@@ -70,51 +71,6 @@ struct dsl_dataset;
 struct dsl_crypto_params;
 
 /*
- * General-purpose 32-bit and 64-bit bitfield encodings.
- */
-#define	BF32_DECODE(x, low, len)	P2PHASE((x) >> (low), 1U << (len))
-#define	BF64_DECODE(x, low, len)	P2PHASE((x) >> (low), 1ULL << (len))
-#define	BF32_ENCODE(x, low, len)	(P2PHASE((x), 1U << (len)) << (low))
-#define	BF64_ENCODE(x, low, len)	(P2PHASE((x), 1ULL << (len)) << (low))
-
-#define	BF32_GET(x, low, len)		BF32_DECODE(x, low, len)
-#define	BF64_GET(x, low, len)		BF64_DECODE(x, low, len)
-
-#define	BF32_SET(x, low, len, val) do { \
-	ASSERT3U(val, <, 1U << (len)); \
-	ASSERT3U(low + len, <=, 32); \
-	(x) ^= BF32_ENCODE((x >> low) ^ (val), low, len); \
-_NOTE(CONSTCOND) } while (0)
-
-#define	BF64_SET(x, low, len, val) do { \
-	ASSERT3U(val, <, 1ULL << (len)); \
-	ASSERT3U(low + len, <=, 64); \
-	((x) ^= BF64_ENCODE((x >> low) ^ (val), low, len)); \
-_NOTE(CONSTCOND) } while (0)
-
-#define	BF32_GET_SB(x, low, len, shift, bias)	\
-	((BF32_GET(x, low, len) + (bias)) << (shift))
-#define	BF64_GET_SB(x, low, len, shift, bias)	\
-	((BF64_GET(x, low, len) + (bias)) << (shift))
-
-/*
- * We use ASSERT3U instead of ASSERT in these macros to prevent a lint error in
- * the case where val is a constant.  We can't fix ASSERT because it's used as
- * an expression in several places in the kernel; as a result, changing it to
- * the do{} while() syntax to allow us to _NOTE the CONSTCOND is not an option.
- */
-#define	BF32_SET_SB(x, low, len, shift, bias, val) do { \
-	ASSERT3U(IS_P2ALIGNED(val, 1U << shift), !=, B_FALSE); \
-	ASSERT3S((val) >> (shift), >=, bias); \
-	BF32_SET(x, low, len, ((val) >> (shift)) - (bias)); \
-_NOTE(CONSTCOND) } while (0)
-#define	BF64_SET_SB(x, low, len, shift, bias, val) do { \
-	ASSERT3U(IS_P2ALIGNED(val, 1ULL << shift), !=, B_FALSE); \
-	ASSERT3S((val) >> (shift), >=, bias); \
-	BF64_SET(x, low, len, ((val) >> (shift)) - (bias)); \
-_NOTE(CONSTCOND) } while (0)
-
-/*
  * We currently support block sizes from 512 bytes to 16MB.
  * The benefits of larger blocks, and thus larger IO, need to be weighed
  * against the cost of COWing a giant block to modify one byte, and the
diff --git a/include/sys/space_reftree.h b/include/sys/space_reftree.h
index 249b15be6..ca9d41dc1 100644
--- a/include/sys/space_reftree.h
+++ b/include/sys/space_reftree.h
@@ -31,7 +31,7 @@
 #define	_SYS_SPACE_REFTREE_H
 
 #include <sys/range_tree.h>
-
+#include <sys/avl.h>
 #ifdef	__cplusplus
 extern "C" {
 #endif
diff --git a/include/sys/vdev.h b/include/sys/vdev.h
index 0d0d0234e..c2fbcc549 100644
--- a/include/sys/vdev.h
+++ b/include/sys/vdev.h
@@ -96,8 +96,8 @@ extern void vdev_metaslab_set_size(vdev_t *);
 extern void vdev_expand(vdev_t *vd, uint64_t txg);
 extern void vdev_split(vdev_t *vd);
 extern void vdev_deadman(vdev_t *vd, char *tag);
-extern void vdev_xlate(vdev_t *vd, const range_seg_t *logical_rs,
-    range_seg_t *physical_rs);
+extern void vdev_xlate(vdev_t *vd, const range_seg64_t *logical_rs,
+    range_seg64_t *physical_rs);
 
 extern void vdev_get_stats_ex(vdev_t *vd, vdev_stat_t *vs, vdev_stat_ex_t *vsx);
 extern void vdev_get_stats(vdev_t *vd, vdev_stat_t *vs);
diff --git a/include/sys/vdev_impl.h b/include/sys/vdev_impl.h
index c179191e3..ae82b75c0 100644
--- a/include/sys/vdev_impl.h
+++ b/include/sys/vdev_impl.h
@@ -86,8 +86,8 @@ typedef void	vdev_remap_func_t(vdev_t *vd, uint64_t offset, uint64_t size,
  * Given a target vdev, translates the logical range "in" to the physical
  * range "res"
  */
-typedef void vdev_xlation_func_t(vdev_t *cvd, const range_seg_t *in,
-    range_seg_t *res);
+typedef void vdev_xlation_func_t(vdev_t *cvd, const range_seg64_t *in,
+    range_seg64_t *res);
 
 typedef const struct vdev_ops {
 	vdev_open_func_t		*vdev_op_open;
@@ -526,8 +526,8 @@ extern vdev_ops_t vdev_indirect_ops;
 /*
  * Common size functions
  */
-extern void vdev_default_xlate(vdev_t *vd, const range_seg_t *in,
-    range_seg_t *out);
+extern void vdev_default_xlate(vdev_t *vd, const range_seg64_t *in,
+    range_seg64_t *out);
 extern uint64_t vdev_default_asize(vdev_t *vd, uint64_t psize);
 extern uint64_t vdev_get_min_asize(vdev_t *vd);
 extern void vdev_set_min_asize(vdev_t *vd);