From 12cfbad90e02793b7a71b7591ebd5c3f9228dc5d Mon Sep 17 00:00:00 2001 From: Filipe David Borba Manana Date: Tue, 26 Nov 2013 15:41:47 +0000 Subject: [PATCH] Btrfs: more efficient extent state insertions Currently we do 2 traversals of an inode's extent_io_tree before inserting an extent state structure: 1 to see if a matching extent state already exists and 1 to do the insertion if the fist traversal didn't found such extent state. This change just combines those tree traversals into a single one. While running sysbench tests (random writes) I captured the number of elements in extent_io_tree trees for a while (into a procfs file backed by a seq_list from seq_file module) and got this histogram: Count: 9310 Range: 51.000 - 21386.000; Mean: 11785.243; Median: 18743.500; Stddev: 8923.688 Percentiles: 90th: 20985.000; 95th: 21155.000; 99th: 21369.000 51.000 - 93.933: 693 ######## 93.933 - 172.314: 938 ########## 172.314 - 315.408: 856 ######### 315.408 - 576.646: 95 # 576.646 - 6415.830: 888 ########## 6415.830 - 11713.809: 1024 ########### 11713.809 - 21386.000: 4816 ##################################################### So traversing such trees can take some significant time that can easily be avoided. Ran the following sysbench tests, 5 times each, for sequential and random writes, and got the following results: sysbench --test=fileio --file-num=1 --file-total-size=2G \ --file-test-mode=seqwr --num-threads=16 --file-block-size=65536 \ --max-requests=0 --max-time=60 --file-io-mode=sync sysbench --test=fileio --file-num=1 --file-total-size=2G \ --file-test-mode=rndwr --num-threads=16 --file-block-size=65536 \ --max-requests=0 --max-time=60 --file-io-mode=sync Before this change: sequential writes: 69.28Mb/sec (average of 5 runs) random writes: 4.14Mb/sec (average of 5 runs) After this change: sequential writes: 69.91Mb/sec (average of 5 runs) random writes: 5.69Mb/sec (average of 5 runs) Signed-off-by: Filipe David Borba Manana Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/extent_io.c | 76 ++++++++++++++++++++++++++++++++------------ 1 file changed, 55 insertions(+), 21 deletions(-) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 01a141245862..5fc9481515f3 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -224,12 +224,20 @@ void free_extent_state(struct extent_state *state) } static struct rb_node *tree_insert(struct rb_root *root, u64 offset, - struct rb_node *node) + struct rb_node *node, + struct rb_node ***p_in, + struct rb_node **parent_in) { struct rb_node **p = &root->rb_node; struct rb_node *parent = NULL; struct tree_entry *entry; + if (p_in && parent_in) { + p = *p_in; + parent = *parent_in; + goto do_insert; + } + while (*p) { parent = *p; entry = rb_entry(parent, struct tree_entry, rb_node); @@ -242,35 +250,43 @@ static struct rb_node *tree_insert(struct rb_root *root, u64 offset, return parent; } +do_insert: rb_link_node(node, parent, p); rb_insert_color(node, root); return NULL; } static struct rb_node *__etree_search(struct extent_io_tree *tree, u64 offset, - struct rb_node **prev_ret, - struct rb_node **next_ret) + struct rb_node **prev_ret, + struct rb_node **next_ret, + struct rb_node ***p_ret, + struct rb_node **parent_ret) { struct rb_root *root = &tree->state; - struct rb_node *n = root->rb_node; + struct rb_node **n = &root->rb_node; struct rb_node *prev = NULL; struct rb_node *orig_prev = NULL; struct tree_entry *entry; struct tree_entry *prev_entry = NULL; - while (n) { - entry = rb_entry(n, struct tree_entry, rb_node); - prev = n; + while (*n) { + prev = *n; + entry = rb_entry(prev, struct tree_entry, rb_node); prev_entry = entry; if (offset < entry->start) - n = n->rb_left; + n = &(*n)->rb_left; else if (offset > entry->end) - n = n->rb_right; + n = &(*n)->rb_right; else - return n; + return *n; } + if (p_ret) + *p_ret = n; + if (parent_ret) + *parent_ret = prev; + if (prev_ret) { orig_prev = prev; while (prev && offset > prev_entry->end) { @@ -292,18 +308,27 @@ static struct rb_node *__etree_search(struct extent_io_tree *tree, u64 offset, return NULL; } -static inline struct rb_node *tree_search(struct extent_io_tree *tree, - u64 offset) +static inline struct rb_node * +tree_search_for_insert(struct extent_io_tree *tree, + u64 offset, + struct rb_node ***p_ret, + struct rb_node **parent_ret) { struct rb_node *prev = NULL; struct rb_node *ret; - ret = __etree_search(tree, offset, &prev, NULL); + ret = __etree_search(tree, offset, &prev, NULL, p_ret, parent_ret); if (!ret) return prev; return ret; } +static inline struct rb_node *tree_search(struct extent_io_tree *tree, + u64 offset) +{ + return tree_search_for_insert(tree, offset, NULL, NULL); +} + static void merge_cb(struct extent_io_tree *tree, struct extent_state *new, struct extent_state *other) { @@ -385,6 +410,8 @@ static void set_state_bits(struct extent_io_tree *tree, */ static int insert_state(struct extent_io_tree *tree, struct extent_state *state, u64 start, u64 end, + struct rb_node ***p, + struct rb_node **parent, unsigned long *bits) { struct rb_node *node; @@ -397,7 +424,7 @@ static int insert_state(struct extent_io_tree *tree, set_state_bits(tree, state, bits); - node = tree_insert(&tree->state, end, &state->rb_node); + node = tree_insert(&tree->state, end, &state->rb_node, p, parent); if (node) { struct extent_state *found; found = rb_entry(node, struct extent_state, rb_node); @@ -444,7 +471,8 @@ static int split_state(struct extent_io_tree *tree, struct extent_state *orig, prealloc->state = orig->state; orig->start = split; - node = tree_insert(&tree->state, prealloc->end, &prealloc->rb_node); + node = tree_insert(&tree->state, prealloc->end, &prealloc->rb_node, + NULL, NULL); if (node) { free_extent_state(prealloc); return -EEXIST; @@ -783,6 +811,8 @@ __set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, struct extent_state *state; struct extent_state *prealloc = NULL; struct rb_node *node; + struct rb_node **p; + struct rb_node *parent; int err = 0; u64 last_start; u64 last_end; @@ -809,11 +839,12 @@ again: * this search will find all the extents that end after * our range starts. */ - node = tree_search(tree, start); + node = tree_search_for_insert(tree, start, &p, &parent); if (!node) { prealloc = alloc_extent_state_atomic(prealloc); BUG_ON(!prealloc); - err = insert_state(tree, prealloc, start, end, &bits); + err = insert_state(tree, prealloc, start, end, + &p, &parent, &bits); if (err) extent_io_tree_panic(tree, err); @@ -920,7 +951,7 @@ hit_next: * the later extent. */ err = insert_state(tree, prealloc, start, this_end, - &bits); + NULL, NULL, &bits); if (err) extent_io_tree_panic(tree, err); @@ -1006,6 +1037,8 @@ int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, struct extent_state *state; struct extent_state *prealloc = NULL; struct rb_node *node; + struct rb_node **p; + struct rb_node *parent; int err = 0; u64 last_start; u64 last_end; @@ -1033,14 +1066,15 @@ again: * this search will find all the extents that end after * our range starts. */ - node = tree_search(tree, start); + node = tree_search_for_insert(tree, start, &p, &parent); if (!node) { prealloc = alloc_extent_state_atomic(prealloc); if (!prealloc) { err = -ENOMEM; goto out; } - err = insert_state(tree, prealloc, start, end, &bits); + err = insert_state(tree, prealloc, start, end, + &p, &parent, &bits); if (err) extent_io_tree_panic(tree, err); cache_state(prealloc, cached_state); @@ -1137,7 +1171,7 @@ hit_next: * the later extent. */ err = insert_state(tree, prealloc, start, this_end, - &bits); + NULL, NULL, &bits); if (err) extent_io_tree_panic(tree, err); cache_state(prealloc, cached_state);