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author | Filipe David Borba Manana <fdmanana@gmail.com> | 2013-11-25 03:20:46 +0000 |
---|---|---|
committer | Chris Mason <clm@fb.com> | 2014-01-28 13:19:46 -0800 |
commit | 5a4267ca20d4c452a97dace4612f1dfc04147fbd (patch) | |
tree | f3dbf5aaf55c935410943ed6af031641e892b5c1 | |
parent | 1b8e7e45e57cc98bf6c8ab9b3087d634636ba2e6 (diff) | |
download | linux-5a4267ca20d4c452a97dace4612f1dfc04147fbd.tar.bz2 |
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 <fdmanana@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
-rw-r--r-- | fs/btrfs/ctree.c | 20 |
1 files changed, 14 insertions, 6 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 22629809c9c4..11f9a1848c7b 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; } |