Btrfs: More throttle tuning

* Make walk_down_tree wake up throttled tasks more often
* Make walk_down_tree call cond_resched during long loops
* As the size of the ref cache grows, wait longer in throttle
* Get rid of the reada code in walk_down_tree, the leaves don't get
  read anymore, thanks to the ref cache.

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

1 files changed, 12 insertions, 47 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 98a1c0faedae..1aeb695078b9 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2369,6 +2369,11 @@ static int noinline drop_leaf_ref_no_cache(struct btrfs_trans_handle *trans,
                                 leaf_owner, leaf_generation,
                                 key.objectid, key.offset, 0);
                 mutex_unlock(&root->fs_info->alloc_mutex);
+
+                atomic_inc(&root->fs_info->throttle_gen);
+                wake_up(&root->fs_info->transaction_throttle);
+                cond_resched();
+
                 BUG_ON(ret);
         }
         return 0;
@@ -2389,6 +2394,11 @@ static int noinline drop_leaf_ref(struct btrfs_trans_handle *trans,
                                         ref->owner, ref->generation,
                                         info->objectid, info->offset, 0);
                 mutex_unlock(&root->fs_info->alloc_mutex);
+
+                atomic_inc(&root->fs_info->throttle_gen);
+                wake_up(&root->fs_info->transaction_throttle);
+                cond_resched();
+
                 BUG_ON(ret);
                 info++;
         }
@@ -2396,51 +2406,6 @@ static int noinline drop_leaf_ref(struct btrfs_trans_handle *trans,
         return 0;
 }
 
-static void noinline reada_walk_down(struct btrfs_root *root,
-                                     struct extent_buffer *node,
-                                     int slot)
-{
-        u64 bytenr;
-        u64 last = 0;
-        u32 nritems;
-        u32 refs;
-        u32 blocksize;
-        int ret;
-        int i;
-        int level;
-        int skipped = 0;
-
-        nritems = btrfs_header_nritems(node);
-        level = btrfs_header_level(node);
-        if (level)
-                return;
-
-        for (i = slot; i < nritems && skipped < 32; i++) {
-                bytenr = btrfs_node_blockptr(node, i);
-                if (last && ((bytenr > last && bytenr - last > 32 * 1024) ||
-                             (last > bytenr && last - bytenr > 32 * 1024))) {
-                        skipped++;
-                        continue;
-                }
-                blocksize = btrfs_level_size(root, level - 1);
-                if (i != slot) {
-                        ret = lookup_extent_ref(NULL, root, bytenr,
-                                                blocksize, &refs);
-                        BUG_ON(ret);
-                        if (refs != 1) {
-                                skipped++;
-                                continue;
-                        }
-                }
-                ret = readahead_tree_block(root, bytenr, blocksize,
-                                           btrfs_node_ptr_generation(node, i));
-                last = bytenr + blocksize;
-                cond_resched();
-                if (ret)
-                        break;
-        }
-}
-
 int drop_snap_lookup_refcount(struct btrfs_root *root, u64 start, u64 len,
                               u32 *refs)
 {
@@ -2549,6 +2514,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
 
                         atomic_inc(&root->fs_info->throttle_gen);
                         wake_up(&root->fs_info->transaction_throttle);
+                        cond_resched();
 
                         continue;
                 }
@@ -2578,8 +2544,6 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
                 if (!next || !btrfs_buffer_uptodate(next, ptr_gen)) {
                         free_extent_buffer(next);
 
-                        if (path->slots[*level] == 0)
-                                reada_walk_down(root, cur, path->slots[*level]);
                         next = read_tree_block(root, bytenr, blocksize,
                                                ptr_gen);
                         cond_resched();
@@ -2601,6 +2565,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
                 path->nodes[*level-1] = next;
                 *level = btrfs_header_level(next);
                 path->slots[*level] = 0;
+                cond_resched();
         }
 out:
         WARN_ON(*level < 0);