Re: 2.6.19-rc1-mm1

[Andrew Morton <akpm@osdl.org>]

On Tue, 10 Oct 2006 08:19:50 -0400
Theodore Tso <tytso@mit.edu> wrote:

> On Tue, Oct 10, 2006 at 12:09:28AM -0700, Andrew Morton wrote:
> > 
> > - Added the ext4 filesystem.  Quick usage instructions:
> > 
> >   - Grab updated e2fsprogs from
> >     ftp://ftp.kernel.org/pub/linux/kernel/people/tytso/e2fsprogs-interim/
> > 
> >   - It's still mke2fs -j /dev/hda1
> > 
> >   - mount /dev/hda1 /wherever -t ext4dev
> > 
> >   - To enable extents,
> > 
> > 	mount /dev/hda1 /wherever -t ext4dev -o extents
> 
> Looks like you didn't take the updated patch from Shaggy which
> requires that you use tune2fs -O extents first?

Nope.  That would have made extents inaccessible with the e2fsprogs I was
using and I didn't have time to test e2fsprogs-interim.

>  (This requires the
> e2fsprogs-interim patches.)

OK.

> The plan is that mount -o extents is not going to be the long-term way
> that extents will be enabled.  I can imagine a -o noextents option,
> which might be used with remount to do an on-line rollback from
> extents to non-extents, but normally you shouldn't need to use a mount
> option to enable a feature that are filesystem format-related.  Those
> should be implied by the appropriate flags in the superblock.
> 
> Mount -o nobh is a different story, since that's just a implementation
> detail --- although for ext4, maybe we should just make nobh a
> default, since that way more people will test it and hopefully,
> eventually nobh will be the only way of doing things, right?

nobh might be inefficient with large PAGE_SIZE and small files (or just
small writes).

> >     Making the journal larger than the mke2fs default often helps
> >     performance with metadata-intensive workloads.
> 
> The default was increased significantly in e2fsprogs 1.40; if someone
> who has their favorite metadata-intesive benchmark could test and see
> if we should be using even larger defaults for certain "mke2fs -T 
> <workload-type>" configurations, I'd really appreciate it.
> 
> 					- Ted