ext4: Use readahead when reading an inode from the inode table
With modern hard drives, reading 64k takes roughly the same time as
reading a 4k block. So request readahead for adjacent inode table
blocks to reduce the time it takes when iterating over directories
(especially when doing this in htree sort order) in a cold cache case.
With this patch, the time it takes to run "git status" on a kernel
tree after flushing the caches via "echo 3 > /proc/sys/vm/drop_caches"
is reduced by 21%.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 163c4452..922d187 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -790,6 +790,8 @@
#define EXT4_DEF_RESUID 0
#define EXT4_DEF_RESGID 0
+#define EXT4_DEF_INODE_READAHEAD_BLKS 32
+
/*
* Default mount options
*/