4 files changed, 46 insertions, 4 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 3cebb4aeddc7..ca6bcc33d033 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1360,6 +1360,7 @@ struct btrfs_fs_info {
 
         u64 generation;
         u64 last_trans_committed;
+        u64 avg_delayed_ref_runtime;
 
         /*
          * this is updated to the current trans every time a full commit
@@ -3172,6 +3173,8 @@ static inline u64 btrfs_calc_trunc_metadata_size(struct btrfs_root *root,
 
 int btrfs_should_throttle_delayed_refs(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root);
+int btrfs_check_space_for_delayed_refs(struct btrfs_trans_handle *trans,
+                                       struct btrfs_root *root);
 void btrfs_put_block_group(struct btrfs_block_group_cache *cache);
 int btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,
                            struct btrfs_root *root, unsigned long count);
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index ed23127a4b02..f0e7bbe14823 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2185,7 +2185,7 @@ int open_ctree(struct super_block *sb,
         fs_info->free_chunk_space = 0;
         fs_info->tree_mod_log = RB_ROOT;
         fs_info->commit_interval = BTRFS_DEFAULT_COMMIT_INTERVAL;
-
+        fs_info->avg_delayed_ref_runtime = div64_u64(NSEC_PER_SEC, 64);
         /* readahead state */
         INIT_RADIX_TREE(&fs_info->reada_tree, GFP_NOFS & ~__GFP_WAIT);
         spin_lock_init(&fs_info->reada_lock);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index c77156c77de7..b5322596d60b 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2322,8 +2322,10 @@ static noinline int __btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,
         struct btrfs_delayed_ref_head *locked_ref = NULL;
         struct btrfs_delayed_extent_op *extent_op;
         struct btrfs_fs_info *fs_info = root->fs_info;
+        ktime_t start = ktime_get();
         int ret;
         unsigned long count = 0;
+        unsigned long actual_count = 0;
         int must_insert_reserved = 0;
 
         delayed_refs = &trans->transaction->delayed_refs;
@@ -2452,6 +2454,7 @@ static noinline int __btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,
                                  &delayed_refs->href_root);
                         spin_unlock(&delayed_refs->lock);
                 } else {
+                        actual_count++;
                         ref->in_tree = 0;
                         rb_erase(&ref->rb_node, &locked_ref->ref_root);
                 }
@@ -2502,6 +2505,26 @@ static noinline int __btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,
                 count++;
                 cond_resched();
         }
+
+        /*
+         * We don't want to include ref heads since we can have empty ref heads
+         * and those will drastically skew our runtime down since we just do
+         * accounting, no actual extent tree updates.
+         */
+        if (actual_count > 0) {
+                u64 runtime = ktime_to_ns(ktime_sub(ktime_get(), start));
+                u64 avg;
+
+                /*
+                 * We weigh the current average higher than our current runtime
+                 * to avoid large swings in the average.
+                 */
+                spin_lock(&delayed_refs->lock);
+                avg = fs_info->avg_delayed_ref_runtime * 3 + runtime;
+                avg = div64_u64(avg, 4);
+                fs_info->avg_delayed_ref_runtime = avg;
+                spin_unlock(&delayed_refs->lock);
+        }
         return 0;
 }
 
@@ -2600,7 +2623,7 @@ static inline u64 heads_to_leaves(struct btrfs_root *root, u64 heads)
         return div64_u64(num_bytes, BTRFS_LEAF_DATA_SIZE(root));
 }
 
-int btrfs_should_throttle_delayed_refs(struct btrfs_trans_handle *trans,
+int btrfs_check_space_for_delayed_refs(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root)
 {
         struct btrfs_block_rsv *global_rsv;
@@ -2629,6 +2652,22 @@ int btrfs_should_throttle_delayed_refs(struct btrfs_trans_handle *trans,
         return ret;
 }
 
+int btrfs_should_throttle_delayed_refs(struct btrfs_trans_handle *trans,
+                                       struct btrfs_root *root)
+{
+        struct btrfs_fs_info *fs_info = root->fs_info;
+        u64 num_entries =
+                atomic_read(&trans->transaction->delayed_refs.num_entries);
+        u64 avg_runtime;
+
+        smp_mb();
+        avg_runtime = fs_info->avg_delayed_ref_runtime;
+        if (num_entries * avg_runtime >= NSEC_PER_SEC)
+                return 1;
+
+        return btrfs_check_space_for_delayed_refs(trans, root);
+}
+
 /*
  * this starts processing the delayed reference count updates and
  * extent insertions we have queued up so far.  count can be
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index fd1446496fe8..5e2bfdaf8d14 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -645,7 +645,7 @@ static int should_end_transaction(struct btrfs_trans_handle *trans,
                                   struct btrfs_root *root)
 {
         if (root->fs_info->global_block_rsv.space_info->full &&
-            btrfs_should_throttle_delayed_refs(trans, root))
+            btrfs_check_space_for_delayed_refs(trans, root))
                 return 1;
 
         return !!btrfs_block_rsv_check(root, &root->fs_info->global_block_rsv, 5);
@@ -710,7 +710,7 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 
         trans->delayed_ref_updates = 0;
         if (!trans->sync && btrfs_should_throttle_delayed_refs(trans, root)) {
-                cur = max_t(unsigned long, cur, 1);
+                cur = max_t(unsigned long, cur, 32);
                 trans->delayed_ref_updates = 0;
                 btrfs_run_delayed_refs(trans, root, cur);
         }