From: Ted Ts'o <tytso@mit.edu>
To: Phillip Susi <psusi@ubuntu.com>
Cc: Andreas Dilger <adilger@dilger.ca>,
ext4 development <linux-ext4@vger.kernel.org>
Subject: Re: Status of META_BG?
Date: Sun, 18 Mar 2012 16:41:53 -0400 [thread overview]
Message-ID: <20120318204153.GA31682@thunk.org> (raw)
In-Reply-To: <4F622D18.3020805@ubuntu.com>
On Thu, Mar 15, 2012 at 01:55:36PM -0400, Phillip Susi wrote:
> >META_BG addresses both of these issues by distributing the group
> >descriptor blocks into the filesystem for each "meta group" (= the
> >number of groups whose descriptors fit into a single block).
>
> So it puts one GD block at the start of every several block groups?
> Wouldn't that drastically slow down opening/mounting the fs since
> the disk has to seek to every block group?
Not necessarily; right now we pull in every single block group
descriptor at mount time because we need to update s_free_inodes_count
and s_free_blocks_count. If we change things so that we only pull in
the block group descriptors at mount time after a journal replay (but
not after a clean umount, when the last inodes count and free blocks
count should be correctly updated), that would avoid seeking to every
16th block group at mount time.
- Ted
next prev parent reply other threads:[~2012-03-18 20:41 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-15 15:46 Status of META_BG? Phillip Susi
2012-03-15 16:25 ` Andreas Dilger
2012-03-15 17:55 ` Phillip Susi
2012-03-15 21:06 ` Andreas Dilger
2012-03-16 13:42 ` Phillip Susi
2012-03-18 20:41 ` Ted Ts'o [this message]
2012-03-18 23:20 ` Andreas Dilger
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