linux-ext4 - [PATCH] mk2fs lazy_journal

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Message-id: <13A447AA-31C7-4E02-8752-DFF75EA31C2E@sun.com>
Date:	Wed, 10 Feb 2010 04:44:46 -0700
From:	Andreas Dilger <adilger@....com>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	ext4 development <linux-ext4@...r.kernel.org>
Subject: [PATCH] mk2fs lazy_journal_init option

Attached is a patch to skip zeroing of the journal if the "-E  
lazy_journal_init" option is given to mke2fs (named to complement the  
"-E lazy_itable_init" option).  This can speed up format time  
significantly for large journal devices.  There is only a short-term  
risk of problems with the uninitialized journal, until such a time  
that the journal has been overwritten once.

To have any kind of problem with the uninitialized journal, the  
filesystem would have to have been newly reformatted twice nearly in a  
row, and then the node crashes before filling the journal even once,  
and the previously-written content would have to line up precisely on  
disk and also have the same transaction ID.

Patch has been lightly tested, showing mke2fs times steady at 14s for  
a 40GB filesystem, regardless of journal size, while previously it  
took up to 45s for an internal 2GB journal.

Signed-off-by: Andreas Dilger <adilger@....com>

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

Download attachment "e2fsprogs-lazy_journal_init.patch" of type "application/octet-stream" (6087 bytes)