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>

1 files changed, 24 insertions, 10 deletions

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,