From 32c5483a8a13a43264809144210ec114dd70b611 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Tue, 29 Oct 2013 22:11:46 +1100 Subject: xfs: abstract the differences in dir2/dir3 via an ops vector Lots of the dir code now goes through switches to determine what is the correct on-disk format to parse. It generally involves a "xfs_sbversion_hasfoo" check, deferencing the superblock version and feature fields and hence touching several cache lines per operation in the process. Some operations do multiple checks because they nest conditional operations and they don't pass the information in a direct fashion between each other. Hence, add an ops vector to the xfs_inode structure that is configured when the inode is initialised to point to all the correct decode and encoding operations. This will significantly reduce the branchiness and cacheline footprint of the directory object decoding and encoding. This is the first patch in a series of conversion patches. It will introduce the ops structure, the setup of it and add the first operation to the vector. Subsequent patches will convert directory ops one at a time to keep the changes simple and obvious. Just this patch shows the benefit of such an approach on code size. Just converting the two shortform dir operations as this patch does decreases the built binary size by ~1500 bytes: $ size fs/xfs/xfs.o.orig fs/xfs/xfs.o.p1 text data bss dec hex filename 794490 96802 1096 892388 d9de4 fs/xfs/xfs.o.orig 792986 96802 1096 890884 d9804 fs/xfs/xfs.o.p1 $ That's a significant decrease in the instruction cache footprint of the directory code for such a simple change, and indicates that this approach is definitely worth pursuing further. Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig Signed-off-by: Ben Myers --- fs/xfs/Makefile | 1 + 1 file changed, 1 insertion(+) (limited to 'fs/xfs/Makefile') diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile index 33a69fabfd83..c21f43506661 100644 --- a/fs/xfs/Makefile +++ b/fs/xfs/Makefile @@ -66,6 +66,7 @@ xfs-y += xfs_alloc.o \ xfs_bmap_btree.o \ xfs_btree.o \ xfs_da_btree.o \ + xfs_da_format.o \ xfs_dir2.o \ xfs_dir2_block.o \ xfs_dir2_data.o \ -- cgit v1.2.1