Commit 32193c14 authored by Filipe David Borba Manana's avatar Filipe David Borba Manana Committed by Chris Mason
Browse files

Btrfs: faster and more efficient extent map insertion 



Before this change, adding an extent map to the extent map tree of an
inode required 2 tree nevigations:

1) doing a tree navigation to search for an existing extent map starting
   at the same offset or an extent map that overlaps the extent map we
   want to insert;

2) Another tree navigation to add the extent map to the tree (if the
   former tree search didn't found anything).

This change just merges these 2 steps into a single one.
While running first few btrfs xfstests I had noticed these trees easily
had a few hundred elements, and then with the following sysbench test it
reached over 1100 elements very often.

Test:

  sysbench --test=fileio --file-num=32 --file-total-size=10G \
    --file-test-mode=seqwr --num-threads=512 --file-block-size=8192 \
    --max-requests=1000000 --file-io-mode=sync [prepare|run]

(fs created with mkfs.btrfs -l 4096 -f /dev/sdb3 before each sysbench
prepare phase)

Before this patch:

run 1 - 41.894Mb/sec
run 2 - 40.527Mb/sec
run 3 - 40.922Mb/sec
run 4 - 49.433Mb/sec
run 5 - 40.959Mb/sec

average - 42.75Mb/sec

After this patch:

run 1 - 48.036Mb/sec
run 2 - 50.21Mb/sec
run 3 - 50.929Mb/sec
run 4 - 46.881Mb/sec
run 5 - 53.192Mb/sec

average - 49.85Mb/sec

Signed-off-by: default avatarFilipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent 68ba990f

fs/btrfs/extent_map.c

+41 −31
Original line number Diff line number Diff line
@@ -79,12 +79,21 @@ void free_extent_map(struct extent_map *em) 
	}

}



static struct rb_node *tree_insert(struct rb_root *root, u64 offset,

				   struct rb_node *node)

/* simple helper to do math around the end of an extent, handling wrap */

static u64 range_end(u64 start, u64 len)

{

	if (start + len < start)

		return (u64)-1;

	return start + len;

}



static int tree_insert(struct rb_root *root, struct extent_map *em)

{

	struct rb_node **p = &root->rb_node;

	struct rb_node *parent = NULL;

	struct extent_map *entry;

	struct extent_map *entry = NULL;

	struct rb_node *orig_parent = NULL;

	u64 end = range_end(em->start, em->len);



	while (*p) {

		parent = *p;
@@ -92,19 +101,37 @@ static struct rb_node *tree_insert(struct rb_root *root, u64 offset, 


		WARN_ON(!entry->in_tree);



		if (offset < entry->start)

		if (em->start < entry->start)

			p = &(*p)->rb_left;

		else if (offset >= extent_map_end(entry))

		else if (em->start >= extent_map_end(entry))

			p = &(*p)->rb_right;

		else

			return parent;

			return -EEXIST;

	}



	entry = rb_entry(node, struct extent_map, rb_node);

	entry->in_tree = 1;

	rb_link_node(node, parent, p);

	rb_insert_color(node, root);

	return NULL;

	orig_parent = parent;

	while (parent && em->start >= extent_map_end(entry)) {

		parent = rb_next(parent);

		entry = rb_entry(parent, struct extent_map, rb_node);

	}

	if (parent)

		if (end > entry->start && em->start < extent_map_end(entry))

			return -EEXIST;



	parent = orig_parent;

	entry = rb_entry(parent, struct extent_map, rb_node);

	while (parent && em->start < entry->start) {

		parent = rb_prev(parent);

		entry = rb_entry(parent, struct extent_map, rb_node);

	}

	if (parent)

		if (end > entry->start && em->start < extent_map_end(entry))

			return -EEXIST;



	em->in_tree = 1;

	rb_link_node(&em->rb_node, orig_parent, p);

	rb_insert_color(&em->rb_node, root);

	return 0;

}



/*
@@ -310,20 +337,11 @@ int add_extent_mapping(struct extent_map_tree *tree, 
		       struct extent_map *em, int modified)

{

	int ret = 0;

	struct rb_node *rb;

	struct extent_map *exist;



	exist = lookup_extent_mapping(tree, em->start, em->len);

	if (exist) {

		free_extent_map(exist);

		ret = -EEXIST;

	ret = tree_insert(&tree->map, em);

	if (ret)

		goto out;

	}

	rb = tree_insert(&tree->map, em->start, &em->rb_node);

	if (rb) {

		ret = -EEXIST;

		goto out;

	}



	atomic_inc(&em->refs);



	em->mod_start = em->start;
@@ -337,14 +355,6 @@ out: 
	return ret;

}



/* simple helper to do math around the end of an extent, handling wrap */

static u64 range_end(u64 start, u64 len)

{

	if (start + len < start)

		return (u64)-1;

	return start + len;

}



static struct extent_map *

__lookup_extent_mapping(struct extent_map_tree *tree,

			u64 start, u64 len, int strict)

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