linux-ext4 - Re: [PATCH] Add ext3 data=guarded mode

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Message-ID: <20090417201342.GF26479@mit.edu>
Date:	Fri, 17 Apr 2009 16:13:42 -0400
From:	Theodore Tso <tytso@....edu>
To:	Amit Shah <amit.shah@...hat.com>
Cc:	Chris Mason <chris.mason@...cle.com>, Jan Kara <jack@...e.cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Developers List <linux-kernel@...r.kernel.org>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] Add ext3 data=guarded mode

On Fri, Apr 17, 2009 at 11:39:06PM +0530, Amit Shah wrote:
> # 4GiB file, kernel 9f76208c33984ab777eace5d07a4e36e88703e02 + ext3-guarded
> 
> filesystem	posix-fallocate	mmap	chunk-4096	chunk-8192
> ext3-guarded	85		97	459		90
> ext3-writeback 86		95	140		94
> ext3-ordered	86		96	277		95
> 
> Running the test in single user mode, I get the following results:
> 
> # 4GiB file, kernel 9f76208c33984ab777eace5d07a4e36e88703e02 + ext3-guarded
> 
> filesystem	posix-fallocate	mmap	chunk-4096	chunk-8192
> ext3-guarded	84		86	163		91
> ext3-writeback 84		88	217		91
> ext3-ordered	84		86	226		91


The difference between guarded and writeback in chunk-4096 looking at
your desktop timings and your single user times is.... surprising. 

In particular, the fact that the guarded time is 3 times longer than
ext3-writeback when the desktop is running, and 20% faster in single
user mode.  Are these results reproducible?  And do you have any
thoughts as to what might be causing them?

					- Ted
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