linux-ext4 - Re: [PATCH 3/3] Add inode table initialization code into Ext4

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Message-ID: <AANLkTimRZ5Cbi7k+=-fQzc8ywpb6u-s19f7UdFdpMJFt@mail.gmail.com>
Date:	Thu, 26 Aug 2010 19:03:22 +0800
From:	Peng Tao <bergwolf@...il.com>
To:	Lukas Czerner <lczerner@...hat.com>
Cc:	linux-ext4@...r.kernel.org, rwheeler@...hat.com,
	sandeen@...hat.com, jack@...e.cz, tytso@....edu, adilger@...ger.ca
Subject: Re: [PATCH 3/3] Add inode table initialization code into Ext4

Hi, all,

On Sat, Aug 21, 2010 at 1:51 AM, Lukas Czerner <lczerner@...hat.com> wrote:
> When lazy_itable_init extended option is passed to mke2fs, it
> considerably speed up filesystem creation because inode tables are left
> uninitialized, thus contains some old data. When this fs is mounted
> filesystem code should initialize (zero out) uninitialized inode table.
> So far this code was missing for ext4 and this patch adds this feature.
>
> When file system is mounted with "inititable" mount option, new thread
> (called itableinitd) is created. This thread walks through allocation
> groups searching for the group with not yet initialized inode table.
> When such a group is found it write zeroes through whole inode table and
> put itself into sleep for defined number of seconds to not disturb other
> ongoing I/O. This is repeated until it walks through every allocation group
> then the iitableinitd thread is stopped.
This will slow down e2fsck speed that is gained from uninitialized
italbe. Am I missing something? What about having another block group
flag to tell itable that is just zeroed but not used, from itable that
is already in use?


-- 
Thanks,
-Bergwolf
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