Btrfs: Throttle tuning

This avoids waiting for transactions with pages locked by breaking out
the code to wait for the current transaction to close into a function
called by btrfs_throttle.

It also lowers the limits for where we start throttling.

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

3 files changed, 31 insertions, 12 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 4765248000fd..b003b4364ddb 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2526,6 +2526,9 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
                                 *level = 0;
                                 break;
                         }
+                        if (printk_ratelimit())
+                                printk("leaf ref miss for bytenr %llu\n",
+                                       (unsigned long long)bytenr);
                 }
                 next = btrfs_find_tree_block(root, bytenr, blocksize);
                 if (!next || !btrfs_buffer_uptodate(next, ptr_gen)) {
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 388ac397c2c8..d3f2fe0b7c6c 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -253,7 +253,7 @@ static int noinline dirty_and_release_pages(struct btrfs_trans_handle *trans,
         end_of_last_block = start_pos + num_bytes - 1;
 
         lock_extent(io_tree, start_pos, end_of_last_block, GFP_NOFS);
-        trans = btrfs_start_transaction(root, 1);
+        trans = btrfs_join_transaction(root, 1);
         if (!trans) {
                 err = -ENOMEM;
                 goto out_unlock;
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 52c5524896a3..66af5140c8ce 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -124,17 +124,12 @@ static noinline int record_root_in_trans(struct btrfs_root *root)
         return 0;
 }
 
-struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
-                                             int num_blocks, int join)
+static void wait_current_trans(struct btrfs_root *root)
 {
-        struct btrfs_trans_handle *h =
-                kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
         struct btrfs_transaction *cur_trans;
-        int ret;
 
-        mutex_lock(&root->fs_info->trans_mutex);
         cur_trans = root->fs_info->running_transaction;
-        if (cur_trans && cur_trans->blocked && !join) {
+        if (cur_trans && cur_trans->blocked) {
                 DEFINE_WAIT(wait);
                 cur_trans->use_count++;
                 while(1) {
@@ -154,6 +149,18 @@ struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
                 }
                 put_transaction(cur_trans);
         }
+}
+
+struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
+                                             int num_blocks, int join)
+{
+        struct btrfs_trans_handle *h =
+                kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
+        int ret;
+
+        mutex_lock(&root->fs_info->trans_mutex);
+        if (!join)
+                wait_current_trans(root);
         ret = join_transaction(root);
         BUG_ON(ret);
 
@@ -200,7 +207,7 @@ static noinline int wait_for_commit(struct btrfs_root *root,
         return 0;
 }
 
-void btrfs_throttle(struct btrfs_root *root)
+static void throttle_on_drops(struct btrfs_root *root)
 {
         struct btrfs_fs_info *info = root->fs_info;
 
@@ -223,19 +230,28 @@ harder:
                 } while (thr == atomic_read(&info->throttle_gen));
 
                 if (harder_count < 5 &&
-                    info->total_ref_cache_size > 5 * 1024 * 1024) {
+                    info->total_ref_cache_size > 1 * 1024 * 1024) {
                         harder_count++;
                         goto harder;
                 }
 
                 if (harder_count < 10 &&
-                    info->total_ref_cache_size > 10 * 1024 * 1024) {
+                    info->total_ref_cache_size > 5 * 1024 * 1024) {
                         harder_count++;
                         goto harder;
                 }
         }
 }
 
+void btrfs_throttle(struct btrfs_root *root)
+{
+        mutex_lock(&root->fs_info->trans_mutex);
+        wait_current_trans(root);
+        mutex_unlock(&root->fs_info->trans_mutex);
+
+        throttle_on_drops(root);
+}
+
 static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root, int throttle)
 {
@@ -256,7 +272,7 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
         kmem_cache_free(btrfs_trans_handle_cachep, trans);
 
         if (throttle)
-                btrfs_throttle(root);
+                throttle_on_drops(root);
 
         return 0;
 }