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

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Message-ID: <20061101123603.GA7195@atrey.karlin.mff.cuni.cz>
Date:	Wed, 1 Nov 2006 13:36:03 +0100
From:	Pavel Machek <pavel@....cz>
To:	Nigel Cunningham <ncunningham@...uxmail.org>
Cc:	Christoph Hellwig <hch@...radead.org>,
	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?

That does not look that scary... just do it.
				Pavel

-- 
Thanks, Sharp!
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