linux-kernel - Re: [PATCH][RFC] fast file mapping for loop

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Date:	Thu, 10 Jan 2008 12:42:25 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	linux-kernel@...r.kernel.org, chris.mason@...cle.com,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH][RFC] fast file mapping for loop

On Wednesday 09 January 2008 19:52, Jens Axboe wrote:

> So how does it work? Instead of punting IO to a thread and passing it
> through the page cache, we instead attempt to send the IO directly to the
> filesystem block that it maps to.

You told Christoph that just using direct-IO from kernel still doesn't
give you the required behaviour... What about queueing the IO directly
*and* using direct-IO? I guess it still has to go through the underlying
filesystem, but that's probably a good thing.

> loop maintains a prio tree of known 
> extents in the file (populated lazily on demand, as needed).

Just a quick question (I haven't looked closely at the code): how come
you are using a prio tree for extents? I don't think they could be
overlapping?
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