linux-ext4 - Bad performance results with the latest git patches

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Date:	Fri, 07 Sep 2007 14:24:47 +0200
From:	Valerie Clement <valerie.clement@...l.net>
To:	Alex Tomas <alex@...sterfs.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Bad performance results with the latest git patches

Hi Alex,

running ffsb tests (large files creation) on my system with the latest 
ext4 git patches against a 2.6.23-rc4 kernel, I've got very bad 
performance results: the I/O throughput measured on an ext4 filesystem 
is ten times lower than those measured on an XFS filesystem on the same 
machine.
I have mounted the ext4 filesytem with mballoc, delalloc and 
data=writeback options.

dmesg output shows plenty of error messages like this:

EXT4-fs error (device sdc): ext4_ext_search_right: bad header in inode 
#3745797: unexpected eh_depth - magic f30a, entries 81, max 84(0), depth 
0(1)
EXT4-fs error (device sdc): ext4_ext_search_right: bad header in inode 
#3745797: unexpected eh_depth - magic f30a, entries 81, max 84(0), depth 
0(1)
EXT4-fs error (device sdc): ext4_ext_search_right: bad header in inode 
#3745797: unexpected eh_depth - magic f30a, entries 81, max 84(0), depth 
0(1)
EXT4-fs error (device sdc): ext4_ext_search_right: bad header in inode 
#3745797: unexpected eh_depth - magic f30a, entries 81, max 84(0), depth 
0(1)

If I removed the second call to ext4_ext_check_header() in the 
ext4_ext_search_right() function, the problem disappears, no more error 
messages and better throughput values close to those measured on the XFS 
filesystem.
It seems that the depth value passed in argument is buggy.

In a previous line,
   while (++depth < path->p_depth) {
the depth value is incremented even if we don't enter the loop. Is it 
the problem ?

Could you check this?
Thanks,
   Valérie
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