Btrfs: Allocator improvements

Reduce CPU time searching for free blocks by optimizing find_first_extent_bit

Fix find_free_extent to make better use of the last_alloc hint.  Before it
was often finding blocks just before the hint.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

4 files changed, 70 insertions, 15 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 6f0825b617d1..88e21bdbc478 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -951,7 +951,7 @@ void btrfs_throttle(struct btrfs_root *root)
 void btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr)
 {
         balance_dirty_pages_ratelimited_nr(
-                        root->fs_info->btree_inode->i_mapping, 1);
+                                   root->fs_info->btree_inode->i_mapping, 1);
 }
 
 void btrfs_set_buffer_defrag(struct extent_buffer *buf)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index af5d4a085280..239e9d8669cb 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -188,9 +188,10 @@ static u64 noinline find_search_start(struct btrfs_root *root,
 {
         int ret;
         struct btrfs_block_group_cache *cache = *cache_ret;
+        struct extent_io_tree *free_space_cache;
+        struct extent_state *state;
         u64 last;
         u64 start = 0;
-        u64 end = 0;
         u64 cache_miss = 0;
         u64 total_fs_bytes;
         int wrapped = 0;
@@ -199,6 +200,8 @@ static u64 noinline find_search_start(struct btrfs_root *root,
                 goto out;
         }
         total_fs_bytes = btrfs_super_total_bytes(&root->fs_info->super_copy);
+        free_space_cache = &root->fs_info->free_space_cache;
+
 again:
         ret = cache_block_group(root, cache);
         if (ret)
@@ -206,22 +209,27 @@ again:
 
         last = max(search_start, cache->key.objectid);
 
+        spin_lock_irq(&free_space_cache->lock);
+        state = find_first_extent_bit_state(free_space_cache, last, EXTENT_DIRTY);
         while(1) {
-                ret = find_first_extent_bit(&root->fs_info->free_space_cache,
-                                            last, &start, &end, EXTENT_DIRTY);
-                if (ret) {
+                if (!state) {
                         if (!cache_miss)
                                 cache_miss = last;
+                        spin_unlock_irq(&free_space_cache->lock);
                         goto new_group;
                 }
 
-                start = max(last, start);
-                last = end + 1;
+                start = max(last, state->start);
+                last = state->end + 1;
                 if (last - start < num) {
                         if (last == cache->key.objectid + cache->key.offset)
                                 cache_miss = start;
+                        do {
+                                state = extent_state_next(state);
+                        } while(state && !(state->state & EXTENT_DIRTY));
                         continue;
                 }
+                spin_unlock_irq(&free_space_cache->lock);
                 if (data != BTRFS_BLOCK_GROUP_MIXED &&
                     start + num > cache->key.objectid + cache->key.offset)
                         goto new_group;
@@ -1420,6 +1428,7 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
         struct btrfs_block_group_cache *block_group;
         int full_scan = 0;
         int wrapped = 0;
+        int empty_cluster;
         u64 cached_start;
 
         WARN_ON(num_bytes < root->sectorsize);
@@ -1431,11 +1440,15 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
                 data = BTRFS_BLOCK_GROUP_MIXED;
         }
 
-        if (!data)
+        if (!data) {
                 last_ptr = &root->fs_info->last_alloc;
+                empty_cluster = 128 * 1024;
+        }
 
-        if (data && btrfs_test_opt(root, SSD))
+        if (data && btrfs_test_opt(root, SSD)) {
                 last_ptr = &root->fs_info->last_data_alloc;
+                empty_cluster = 2 * 1024 * 1024;
+        }
 
         if (last_ptr) {
                 if (*last_ptr)
@@ -1443,8 +1456,9 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
                 else {
                         hint_byte = hint_byte &
                                 ~((u64)BTRFS_BLOCK_GROUP_SIZE - 1);
-                        empty_size += 2 * 1024 * 1024;
+                        empty_size += empty_cluster;
                 }
+                search_start = max(search_start, hint_byte);
         }
 
         search_end = min(search_end,
@@ -1476,7 +1490,7 @@ check_failed:
         if (last_ptr && *last_ptr && search_start != *last_ptr) {
                 *last_ptr = 0;
                 if (!empty_size) {
-                        empty_size += 2 * 1024 * 1024;
+                        empty_size += empty_cluster;
                         total_needed += empty_size;
                 }
                 search_start = find_search_start(root, &block_group,
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 9262ab37a7cd..fb6400895ed6 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -255,7 +255,7 @@ static int merge_state(struct extent_io_tree *tree,
                         state->start = other->start;
                         other->tree = NULL;
                         if (tree->last == other)
-                                tree->last = NULL;
+                                tree->last = state;
                         rb_erase(&other->rb_node, &tree->state);
                         free_extent_state(other);
                 }
@@ -268,7 +268,7 @@ static int merge_state(struct extent_io_tree *tree,
                         other->start = state->start;
                         state->tree = NULL;
                         if (tree->last == state)
-                                tree->last = NULL;
+                                tree->last = other;
                         rb_erase(&state->rb_node, &tree->state);
                         free_extent_state(state);
                 }
@@ -397,8 +397,9 @@ static int clear_state_bit(struct extent_io_tree *tree,
         if (delete || state->state == 0) {
                 if (state->tree) {
                         clear_state_cb(tree, state, state->state);
-                        if (tree->last == state)
-                                tree->last = NULL;
+                        if (tree->last == state) {
+                                tree->last = extent_state_next(state);
+                        }
                         rb_erase(&state->rb_node, &tree->state);
                         state->tree = NULL;
                         free_extent_state(state);
@@ -962,6 +963,35 @@ out:
 }
 EXPORT_SYMBOL(find_first_extent_bit);
 
+struct extent_state *find_first_extent_bit_state(struct extent_io_tree *tree,
+                                                 u64 start, int bits)
+{
+        struct rb_node *node;
+        struct extent_state *state;
+
+        /*
+         * this search will find all the extents that end after
+         * our range starts.
+         */
+        node = tree_search(tree, start);
+        if (!node || IS_ERR(node)) {
+                goto out;
+        }
+
+        while(1) {
+                state = rb_entry(node, struct extent_state, rb_node);
+                if (state->end >= start && (state->state & bits)) {
+                        return state;
+                }
+                node = rb_next(node);
+                if (!node)
+                        break;
+        }
+out:
+        return NULL;
+}
+EXPORT_SYMBOL(find_first_extent_bit_state);
+
 u64 find_lock_delalloc_range(struct extent_io_tree *tree,
                              u64 *start, u64 *end, u64 max_bytes)
 {
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 151fdada4dc4..fcc4bb078c24 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -81,6 +81,15 @@ struct extent_buffer {
 
 struct extent_map_tree;
 
+static inline struct extent_state *extent_state_next(struct extent_state *state)
+{
+        struct rb_node *node;
+        node = rb_next(&state->rb_node);
+        if (!node)
+                return NULL;
+        return rb_entry(node, struct extent_state, rb_node);
+}
+
 typedef struct extent_map *(get_extent_t)(struct inode *inode,
                                           struct page *page,
                                           size_t page_offset,
@@ -122,6 +131,8 @@ int set_extent_delalloc(struct extent_io_tree *tree, u64 start, u64 end,
                      gfp_t mask);
 int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
                           u64 *start_ret, u64 *end_ret, int bits);
+struct extent_state *find_first_extent_bit_state(struct extent_io_tree *tree,
+                                                 u64 start, int bits);
 int extent_invalidatepage(struct extent_io_tree *tree,
                           struct page *page, unsigned long offset);
 int extent_write_full_page(struct extent_io_tree *tree, struct page *page,