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Commit 41be1f3b authored by Josef Bacik's avatar Josef Bacik Committed by Chris Mason
Browse files

Btrfs: optimize leaf_space_used 



This gets called at least 4 times for every level while adding an object,
and it involves 3 kmapping calls, which on my box take about 5us a piece.
So instead use a token, which brings us down to 1 kmap call and makes this
function take 1/3 of the time per call.  Thanks,

Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
Signed-off-by: default avatarChris Mason <chris.mason@fusionio.com>
parent ad914559

fs/btrfs/ctree.c

+9 −2
Original line number Diff line number Diff line
@@ -3298,14 +3298,21 @@ static noinline int split_node(struct btrfs_trans_handle *trans, 
 */

static int leaf_space_used(struct extent_buffer *l, int start, int nr)

{

	struct btrfs_item *start_item;

	struct btrfs_item *end_item;

	struct btrfs_map_token token;

	int data_len;

	int nritems = btrfs_header_nritems(l);

	int end = min(nritems, start + nr) - 1;



	if (!nr)

		return 0;

	data_len = btrfs_item_end_nr(l, start);

	data_len = data_len - btrfs_item_offset_nr(l, end);

	btrfs_init_map_token(&token);

	start_item = btrfs_item_nr(l, start);

	end_item = btrfs_item_nr(l, end);

	data_len = btrfs_token_item_offset(l, start_item, &token) +

		btrfs_token_item_size(l, start_item, &token);

	data_len = data_len - btrfs_token_item_offset(l, end_item, &token);

	data_len += sizeof(struct btrfs_item) * nr;

	WARN_ON(data_len < 0);

	return data_len;