Hi,

This patch speeds up e2fsck on Ext3 significantly using a technique 
called Metaclustering. Metaclustering is being discussed on LKML in some 
other threads, here is the latest patch against the 2.6.23.13 stable 
kernel, any help in testing and evaluating this will be greatly 
appreciated! While I'd direct anyone interested in details of 
metaclustering to other LKML threads discussing it, I've enclosed a brief 
description here:

Metaclustering refers to storing indirect blocks in clusters on a 
per-group basis instead of spreading them out along with the data blocks. 
This makes e2fsck faster since it can now read and verify all indirect 
blocks without much seeks. However, done naively it can affect IO 
performance, so we have built in some optimizations to prevent that from 
happening. Finally, the benefit in fsck performance is noticeable only 
when indirect block reads are the bottleneck which is not always the case, 
but quite frequently is, in the case of moderate to large disks with lot 
of data on them. However, when indirect block reads are not the
bottleneck, e2fsck is generally quite fast anyway to warrant any 
performance improvements.

Thanks!
Abhishek

Signed-off-by: Abhishek Rai <abhishekrai@google.com>

diff -rupdN linux-2.6.23.13-clean/fs/ext3/balloc.c linux-2.6.23.13-ext3mc/fs/ext3/balloc.c
--- linux-2.6.23.13-clean/fs/ext3/balloc.c	2008-01-09 12:18:17.000000000 -0500
+++ linux-2.6.23.13-ext3mc/fs/ext3/balloc.c	2008-01-12 23:59:36.000000000 -0500
@@ -33,6 +33,29 @@
   * super block.  Each descriptor contains the number of the bitmap block and
   * the free blocks count in the block.  The descriptors are loaded in memory
   * when a file system is mounted (see ext3_fill_super).
+ *
+ * A note on ext3 metaclustering:
+ *
+ * 	Start of						End of
+ * 	block group						block group
+ * 	 ________________________________________________________________
+ * 	|	NON-MC REGION			|	MC REGION	 |
+ * 	|					|Overflow		 |
+ * 	|Data blocks ...
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This patch does not apply to a clean 2.6.23.13 tree using either of
  patch -p1 <patch.ext3-fsck-faster
  patch -p1 -l <patch.ext3-fsck-faster

Best,
Michael
=2D-=20
 Michael Gerdau       email: mgerdau@tiscali.de
 GPG-keys available on request or at public keyserver
[ message continues ]

"Me too".  Extra spaces seem to have been inserted into the context 
lines.  Abhishek, how about trying this as an attachment while you sort 
out your mailer issues?

Regards,

Daniel
--

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