From 52b029f42751d0aea2d9c05a584438f4f0dfc123 Mon Sep 17 00:00:00 2001 From: Ethan Lien Date: Fri, 19 Aug 2022 10:44:08 +0800 Subject: btrfs: remove unnecessary EXTENT_UPTODATE state in buffered I/O path After we copied data to page cache in buffered I/O, we 1. Insert a EXTENT_UPTODATE state into inode's io_tree, by endio_readpage_release_extent(), set_extent_delalloc() or set_extent_defrag(). 2. Set page uptodate before we unlock the page. But the only place we check io_tree's EXTENT_UPTODATE state is in btrfs_do_readpage(). We know we enter btrfs_do_readpage() only when we have a non-uptodate page, so it is unnecessary to set EXTENT_UPTODATE. For example, when performing a buffered random read: fio --rw=randread --ioengine=libaio --direct=0 --numjobs=4 \ --filesize=32G --size=4G --bs=4k --name=job \ --filename=/mnt/file --name=job Then check how many extent_state in io_tree: cat /proc/slabinfo | grep btrfs_extent_state | awk '{print $2}' w/o this patch, we got 640567 btrfs_extent_state. w/ this patch, we got 204 btrfs_extent_state. Maintaining such a big tree brings overhead since every I/O needs to insert EXTENT_LOCKED, insert EXTENT_UPTODATE, then remove EXTENT_LOCKED. And in every insert or remove, we need to lock io_tree, do tree search, alloc or dealloc extent states. By removing unnecessary EXTENT_UPTODATE, we keep io_tree in a minimal size and reduce overhead when performing buffered I/O. Reviewed-by: Filipe Manana Reviewed-by: Robbie Ko Signed-off-by: Ethan Lien Signed-off-by: David Sterba --- fs/btrfs/extent-io-tree.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'fs/btrfs/extent-io-tree.h') diff --git a/fs/btrfs/extent-io-tree.h b/fs/btrfs/extent-io-tree.h index c3eb52dbe61c..53ae849d0248 100644 --- a/fs/btrfs/extent-io-tree.h +++ b/fs/btrfs/extent-io-tree.h @@ -211,7 +211,7 @@ static inline int set_extent_delalloc(struct extent_io_tree *tree, u64 start, struct extent_state **cached_state) { return set_extent_bit(tree, start, end, - EXTENT_DELALLOC | EXTENT_UPTODATE | extra_bits, + EXTENT_DELALLOC | extra_bits, 0, NULL, cached_state, GFP_NOFS, NULL); } @@ -219,7 +219,7 @@ static inline int set_extent_defrag(struct extent_io_tree *tree, u64 start, u64 end, struct extent_state **cached_state) { return set_extent_bit(tree, start, end, - EXTENT_DELALLOC | EXTENT_UPTODATE | EXTENT_DEFRAG, + EXTENT_DELALLOC | EXTENT_DEFRAG, 0, NULL, cached_state, GFP_NOFS, NULL); } -- cgit v1.2.3-73-gaa49b