Btrfs: use a slab for ordered extents allocation

The ordered extent allocation is in the fast path of the IO, so use a slab
to improve the speed of the allocation.

 "Size of the struct is 280, so this will fall into the size-512 bucket,
  giving 8 objects per page, while own slab will pack 14 objects into a page.

  Another benefit I see is to check for leaked objects when the module is
  removed (and the cache destroy takes place)."
						-- David Sterba

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>

1 files changed, 21 insertions, 2 deletions

diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index cd8ecb73c05c..e2b3d994ec01 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -25,6 +25,8 @@
 #include "btrfs_inode.h"
 #include "extent_io.h"
 
+static struct kmem_cache *btrfs_ordered_extent_cache;
+
 static u64 entry_end(struct btrfs_ordered_extent *entry)
 {
         if (entry->file_offset + entry->len < entry->file_offset)
@@ -187,7 +189,7 @@ static int __btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
         struct btrfs_ordered_extent *entry;
 
         tree = &BTRFS_I(inode)->ordered_tree;
-        entry = kzalloc(sizeof(*entry), GFP_NOFS);
+        entry = kmem_cache_zalloc(btrfs_ordered_extent_cache, GFP_NOFS);
         if (!entry)
                 return -ENOMEM;
 
@@ -421,7 +423,7 @@ void btrfs_put_ordered_extent(struct btrfs_ordered_extent *entry)
                         list_del(&sum->list);
                         kfree(sum);
                 }
-                kfree(entry);
+                kmem_cache_free(btrfs_ordered_extent_cache, entry);
         }
 }
 
@@ -958,3 +960,20 @@ void btrfs_add_ordered_operation(struct btrfs_trans_handle *trans,
         }
         spin_unlock(&root->fs_info->ordered_extent_lock);
 }
+
+int __init ordered_data_init(void)
+{
+        btrfs_ordered_extent_cache = kmem_cache_create("btrfs_ordered_extent",
+                                     sizeof(struct btrfs_ordered_extent), 0,
+                                     SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
+                                     NULL);
+        if (!btrfs_ordered_extent_cache)
+                return -ENOMEM;
+        return 0;
+}
+
+void ordered_data_exit(void)
+{
+        if (btrfs_ordered_extent_cache)
+                kmem_cache_destroy(btrfs_ordered_extent_cache);
+}