From 556b27abf73833923d5cd4be80006292e1b31662 Mon Sep 17 00:00:00 2001 From: Vivek Haldar Date: Wed, 25 May 2011 07:41:54 -0400 Subject: ext4: do not normalize block requests from fallocate() Currently, an fallocate request of size slightly larger than a power of 2 is turned into two block requests, each a power of 2, with the extra blocks pre-allocated for future use. When an application calls fallocate, it already has an idea about how large the file may grow so there is usually little benefit to reserve extra blocks on the preallocation list. This reduces disk fragmentation. Tested: fsstress. Also verified manually that fallocat'ed files are contiguously laid out with this change (whereas without it they begin at power-of-2 boundaries, leaving blocks in between). CPU usage of fallocate is not appreciably higher. In a tight fallocate loop, CPU usage hovers between 5%-8% with this change, and 5%-7% without it. Using a simulated file system aging program which the file system to 70%, the percentage of free extents larger than 8MB (as measured by e2freefrag) increased from 38.8% without this change, to 69.4% with this change. Signed-off-by: Vivek Haldar Signed-off-by: "Theodore Ts'o" --- fs/ext4/extents.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'fs/ext4/extents.c') diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 88ff3a74787..ae65f247ced 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3554,6 +3554,8 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, else /* disable in-core preallocation for non-regular files */ ar.flags = 0; + if (flags & EXT4_GET_BLOCKS_NO_NORMALIZE) + ar.flags |= EXT4_MB_HINT_NOPREALLOC; newblock = ext4_mb_new_blocks(handle, &ar, &err); if (!newblock) goto out2; @@ -3807,7 +3809,8 @@ retry: break; } ret = ext4_map_blocks(handle, inode, &map, - EXT4_GET_BLOCKS_CREATE_UNINIT_EXT); + EXT4_GET_BLOCKS_CREATE_UNINIT_EXT | + EXT4_GET_BLOCKS_NO_NORMALIZE); if (ret <= 0) { #ifdef EXT4FS_DEBUG WARN_ON(ret <= 0); -- cgit v1.2.3