linux-kernel - Re: [PATCH] Use extents for recording what swap is allocated.

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Date:	Tue, 31 Oct 2006 22:38:08 +1100
From:	Nigel Cunningham <ncunningham@...uxmail.org>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Andrew Morton <akpm@...l.org>, "Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Use extents for recording what swap is allocated.

Hi.

On Tue, 2006-10-24 at 21:42 +0100, Christoph Hellwig wrote:
> On Mon, Oct 23, 2006 at 02:14:17PM +1000, Nigel Cunningham wrote:
> > Switch from bitmaps to using extents to record what swap is allocated;
> > they make more efficient use of memory, particularly where the allocated
> > storage is small and the swap space is large.
> >     
> > This is also part of the ground work for implementing support for
> > supporting multiple swap devices.
> 
> In addition to the very useful comments from Rafael there's some observations
> of my own:
> 
>  - there's an awful lot of opencoded list manipulation, any chance you
>    could use list.h instead?

Further to this, I gave using list.h a go. Unfortunately it doesn't look
to me like it is a good idea: in adding a range, I'm comparing the new
range to the maximum of one extent and the minimum of the next, so
finding the minimum of the next extent becomes a lot uglier than it
currently is. Currently it's just ->next->minimum, but with list.h, I'd
need container_of(current->list.next)->minimum. Or am I missing
something?

Regards,

Nigel

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