From 5a4267ca20d4c452a97dace4612f1dfc04147fbd Mon Sep 17 00:00:00 2001 From: Filipe David Borba Manana Date: Mon, 25 Nov 2013 03:20:46 +0000 Subject: [PATCH] Btrfs: try harder to avoid btree node splits When attempting to move items from our target leaf to its neighbor leaves (right and left), we only need to free data_size - free_space bytes from our leaf in order to add the new item (which has size of data_size bytes). Therefore attempt to move items to the right and left leaves if they have at least data_size - free_space bytes free, instead of data_size bytes free. After 5 runs of the following test, I got a smaller number of btree node splits overall: sysbench --test=fileio --file-num=512 --file-total-size=5G \ --file-test-mode=seqwr --num-threads=512 \ --file-block-size=8192 --max-requests=100000 --file-io-mode=sync Before this change: * 6171 splits (average of 5 test runs) * 61.508Mb/sec of throughput (average of 5 test runs) After this change: * 6036 splits (average of 5 test runs) * 63.533Mb/sec of throughput (average of 5 test runs) An ideal test would not just have multiple threads/processes writing to a file (insertion of file extent items) but also do other operations that result in insertion of items with varied sizes, like file/directory creations, creation of links, symlinks, xattrs, etc. Signed-off-by: Filipe David Borba Manana Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/ctree.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 2262980..11f9a18 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -3929,14 +3929,17 @@ static noinline int push_for_double_split(struct btrfs_trans_handle *trans, int progress = 0; int slot; u32 nritems; + int space_needed = data_size; slot = path->slots[0]; + if (slot < btrfs_header_nritems(path->nodes[0])) + space_needed -= btrfs_leaf_free_space(root, path->nodes[0]); /* * try to push all the items after our slot into the * right leaf */ - ret = push_leaf_right(trans, root, path, 1, data_size, 0, slot); + ret = push_leaf_right(trans, root, path, 1, space_needed, 0, slot); if (ret < 0) return ret; @@ -3956,7 +3959,7 @@ static noinline int push_for_double_split(struct btrfs_trans_handle *trans, /* try to push all the items before our slot into the next leaf */ slot = path->slots[0]; - ret = push_leaf_left(trans, root, path, 1, data_size, 0, slot); + ret = push_leaf_left(trans, root, path, 1, space_needed, 0, slot); if (ret < 0) return ret; @@ -4000,13 +4003,18 @@ static noinline int split_leaf(struct btrfs_trans_handle *trans, /* first try to make some room by pushing left and right */ if (data_size && path->nodes[1]) { - wret = push_leaf_right(trans, root, path, data_size, - data_size, 0, 0); + int space_needed = data_size; + + if (slot < btrfs_header_nritems(l)) + space_needed -= btrfs_leaf_free_space(root, l); + + wret = push_leaf_right(trans, root, path, space_needed, + space_needed, 0, 0); if (wret < 0) return wret; if (wret) { - wret = push_leaf_left(trans, root, path, data_size, - data_size, 0, (u32)-1); + wret = push_leaf_left(trans, root, path, space_needed, + space_needed, 0, (u32)-1); if (wret < 0) return wret; } -- 2.7.4