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authorTheodore Ts'o <tytso@mit.edu>2008-10-09 23:53:47 -0400
committerTheodore Ts'o <tytso@mit.edu>2008-10-09 23:53:47 -0400
commit240799cdf22bd789ea6852653c3b879d35ad0a6c (patch)
treee696b60cc103f23838b5c14d8d397f692abffbc3 /Documentation
parent37515facd001942221d68171c81c1f46d54ffdd0 (diff)
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>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/ext4.txt6
-rw-r--r--Documentation/filesystems/proc.txt3
2 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 0d5394920a3..289057958f9 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -177,6 +177,11 @@ barrier=<0|1(*)> This enables/disables the use of write barriers in
your disks are battery-backed in one way or another,
disabling barriers may safely improve performance.
+inode_readahead=n This tuning parameter controls the maximum
+ number of inode table blocks that ext4's inode
+ table readahead algorithm will pre-read into
+ the buffer cache. The default value is 32 blocks.
+
orlov (*) This enables the new Orlov block allocator. It is
enabled by default.
@@ -252,6 +257,7 @@ stripe=n Number of filesystem blocks that mballoc will try
delalloc (*) Deferring block allocation until write-out time.
nodelalloc Disable delayed allocation. Blocks are allocation
when data is copied from user to page cache.
+
Data Mode
=========
There are 3 different data modes:
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index d9ac9706735..d831d24d2a6 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -956,6 +956,9 @@ Table 1-10: Files in /proc/fs/ext4/<devname>
files are packed closely together. Each large file
will have its blocks allocated out of its own unique
preallocation pool.
+inode_readahead Tuning parameter which controls the maximum number of
+ inode table blocks that ext4's inode table readahead
+ algorithm will pre-read into the buffer cache
..............................................................................