Date: Thu, 26 Mar 2009 15:57:25 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>, Ingo Molnar <mingo@elte.hu>,
       Theodore Tso <tytso@mit.edu>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
       Arjan van de Ven <arjan@infradead.org>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, Nick Piggin <npiggin@suse.de>,
       Jens Axboe <jens.axboe@oracle.com>, David Rees <drees76@gmail.com>,
       Jesper Krogh <jesper@krogh.cc>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Oleg Nesterov <oleg@redhat.com>, Roland McGrath <roland@redhat.com>
Subject: Re: ext3 IO latency measurements (was: Linux 2.6.29)
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On Thu, 26 Mar 2009 15:39:53 -0700 (PDT) Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Thu, 26 Mar 2009, Jan Kara wrote:
> >
> >   Reads are measurably better with the patch - the test with cat you
> > describe below took ~0.5s per file without the patch and always less than
> > 0.02s with the patch. So it seems to help something.
> 
> That would seem to be a _huge_ improvement.

It's strange that we still don't have an ext3_writepages().  Open a
transaction, do a large pile of writes, close the transaction again. 
We don't even have a data=writeback writepages() implementation, which
should be fairly simple.

Bizarre.

Mingming had a shot at it a few years ago and I think Badari did as
well, but I guess it didn't work out.

Falling back to generic_writepages() on our main local fs is a bit lame.
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