Date: Thu, 26 Mar 2009 19:00:10 +0000 (GMT)
From: Hugh Dickins <hugh@veritas.com>
To: Jens Axboe <jens.axboe@oracle.com>
cc: Ric Wheeler <rwheeler@redhat.com>, Jeff Garzik <jeff@garzik.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Theodore Tso <tytso@mit.edu>, Ingo Molnar <mingo@elte.hu>,
       Alan Cox <alan@lxorguk.ukuu.org.uk>,
       Arjan van de Ven <arjan@infradead.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, Nick Piggin <npiggin@suse.de>,
       David Rees <drees76@gmail.com>, Jesper Krogh <jesper@krogh.cc>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Linux 2.6.29
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On Thu, 26 Mar 2009, Jens Axboe wrote:
> On Thu, Mar 26 2009, Hugh Dickins wrote:
> > 
> > So, directing a barrier (WRITE_BARRIER or DISCARD_BARRIER) to a range
> > of sectors in one partition interposes a barrier into the queue of I/O
> > across (all partitions of) that whole device.
> 
> Correct
> 
> > I think that's not how filesystems really want barriers to behave,
> > and might tend to discourage us from using barriers more freely.
> > But I have zero appreciation of whether it's a significant issue
> > worth non-trivial change - just wanted to get it out into the open.
> 
> Per-partition definitely makes sense. The problem is that we do sorting
> on a per-device basis right now. But it's a good point, I'll try and
> take a look at how much work it would be to make it per-partition
> instead. It wont be trivial :-)

Thanks, that would be interesting.
Trivial bores you anyway, doesn't it?

Hugh
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