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Re: htree 2.4.19-dxdir patch

On Mon, Sep 23, 2002 at 01:28:56PM +0200, Marc-Christian Petersen wrote:
> On Monday 23 September 2002 01:33, Theodore Ts'o wrote:
> Hi Theodore,
> > These times don't look right.  Are you sure you created the filesystem
> > was using directorying indexing turned on?  With it turned on,
> > creating 100,000 files should take 10-20 seconds depending on the
> > speed of your system and hard disks.
> hmm, I thought this will also work if I just mount with index option on my 
> already working filesystems. But I was wrong, obviously.

I've never liked the index mount option, and I'm going to be taking
that out of the patch that I send to Linus.  It's just too confusing,
and its effects were not what I would consider consistent.

> Can you tell me why this only works with new created filesystems with index 
> and not with already created filesystems just using the index mount option?

It works with already created filesystems, but just don't use the
index mount option.  As I said, it confuses people....

If you want to convert any filesystem to use directory indexing, all
you need to do is use the following commands:

	debugfs -w -R "features dir_index" /dev/hdXXX
	debugfs -w -R "ssv def_hash_version tea" /dev/hdXXX
	debugfs -w -R "ssv hash_seed random" /dev/hdXXX

or if you prefer...

	% debugfs -w test.img
	debugfs: features dir_index
	debugfs: ssv def_hash_version tea
	debugfs: ssv hash_seed random
	debugfs: quit

With the soon-to-be-released e2fsprogs 1.29, you'll be able to do this
via the single command:

	tune2fs -O dir_index /dev/hdXXX

... but this won't work e2fsprogs 1.28.  

You will need to remount the filesystem before the dir_index option
will take effect.  (Umount followed by mount will definitely work.
Using mount -o remount should work, but I haven't had a chance to test
that kernel code path yet.)

> > On my system, creating the files in the test3 directory takes 11.408
> > seconds real time, with 6.221 seconds of system time with the
> > directory indexing.  If I comment out the debugfs line which activates
> > the "dir_index" filesystem feature flag, then directory indexing is
> > turned off, and the script takes 38:07 minutes of real time, with
> > 38:05 of it being system time.
> jep, exakt. with index, your script took 15 seconds! FAAST :)

Well, yes, that's the point of the dir_index feature.  :-)

						- Ted

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