| Message ID | 20200527101059.7391-1-nborisov@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: remove redundant local var in read_block_for_search | expand |
Looks good,
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
On Wed, May 27, 2020 at 01:10:59PM +0300, Nikolay Borisov wrote: > The local 'b' variable is only used to directly read values from passed > extent buffer. So eliminate it and directly use the input parameter. Furthermore > this shrinks the size of the following functions: > > ./scripts/bloat-o-meter ctree.orig fs/btrfs/ctree.o > add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-73 (-73) > Function old new delta > read_block_for_search.isra 876 871 -5 > push_node_left 1112 1044 -68 > Total: Before=50348, After=50275, chg -0.14% > > Signed-off-by: Nikolay Borisov <nborisov@suse.com> Added to misc-next, thanks.
On Wed, May 27, 2020 at 01:10:59PM +0300, Nikolay Borisov wrote: > The local 'b' variable is only used to directly read values from passed > extent buffer. So eliminate it and directly use the input parameter. Furthermore > this shrinks the size of the following functions: > > ./scripts/bloat-o-meter ctree.orig fs/btrfs/ctree.o > add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-73 (-73) > Function old new delta > read_block_for_search.isra 876 871 -5 > push_node_left 1112 1044 -68 > - struct extent_buffer *b = *eb_ret; > - blocknr = btrfs_node_blockptr(b, slot); > - gen = btrfs_node_ptr_generation(b, slot); > - parent_level = btrfs_header_level(b); > - btrfs_node_key_to_cpu(b, &first_key, slot); > + blocknr = btrfs_node_blockptr(*eb_ret, slot); > + gen = btrfs_node_ptr_generation(*eb_ret, slot); > + parent_level = btrfs_header_level(*eb_ret); > + btrfs_node_key_to_cpu(*eb_ret, &first_key, slot); It's interesting how such trivial and obvious change can improve the code generation. The removed indirection resulted in smaller function push_node_left that is not even called directly, but as there are lot of static helpers it's some intra-procedural pass that can utilize the reduced variable indirection.
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 3ab307b4b294..72a3389d2d87 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -2335,16 +2335,15 @@ read_block_for_search(struct btrfs_root *root, struct btrfs_path *p, struct btrfs_fs_info *fs_info = root->fs_info; u64 blocknr; u64 gen; - struct extent_buffer *b = *eb_ret; struct extent_buffer *tmp; struct btrfs_key first_key; int ret; int parent_level; - blocknr = btrfs_node_blockptr(b, slot); - gen = btrfs_node_ptr_generation(b, slot); - parent_level = btrfs_header_level(b); - btrfs_node_key_to_cpu(b, &first_key, slot); + blocknr = btrfs_node_blockptr(*eb_ret, slot); + gen = btrfs_node_ptr_generation(*eb_ret, slot); + parent_level = btrfs_header_level(*eb_ret); + btrfs_node_key_to_cpu(*eb_ret, &first_key, slot); tmp = find_extent_buffer(fs_info, blocknr); if (tmp) {
The local 'b' variable is only used to directly read values from passed extent buffer. So eliminate it and directly use the input parameter. Furthermore this shrinks the size of the following functions: ./scripts/bloat-o-meter ctree.orig fs/btrfs/ctree.o add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-73 (-73) Function old new delta read_block_for_search.isra 876 871 -5 push_node_left 1112 1044 -68 Total: Before=50348, After=50275, chg -0.14% Signed-off-by: Nikolay Borisov <nborisov@suse.com> --- fs/btrfs/ctree.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) -- 2.17.1