linux-ext4 - Re: [PATCH RFC 1/2] ext4: speed-up truncate/unlink

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Message-ID: <20120918041006.GC32195@thunk.org>
Date:	Tue, 18 Sep 2012 00:10:06 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Andrey Sidorov <qrxd43@...orola.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH RFC 1/2] ext4: speed-up truncate/unlink

On Tue, Sep 18, 2012 at 01:00:30AM +0400, Andrey Sidorov wrote:
> Do not iterate over data blocks scanning for bh's to forget as they're
> never exist. This improves time taken by unlink / truncate syscall.
> Tested by continuously truncating file that is being written by dd.
> Another test is rm -rf of linux tree while tar unpacks it. With
> ordered data mode condition unlikely(!tbh) was always met in
> ext4_free_blocks. With journal data mode tbh was found only few times,
> so optimisation is also possible.

Thanks for this patch.  It's good you did the testing, although from a
theoretical point of view I'm sure it's sound because the only case
where journal=data mode will there be data blocks in the buffer cache.
In the other cases, the data is cached in the page cache, so it's a
waste of time looking up the blocks so they can be bforgotten.

The one thing which is missing from your patch is a Signed-off-by:
footer.  This has a specific legal meaning.  See:

	http://elinux.org/Developer_Certificate_Of_Origin

You don't need to resend this patch, though; just reply with an
acknowledgement that you agree to add your DCO to the patch:

Signed-off-by: Andrey Sidorov <qrxd43@...orola.com>

Thanks for contributing to the ext4 file system!

						- Ted
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