linux-kernel - Re: New filesystem for Linux

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Message-ID: <454E46A8.20106@zytor.com>
Date:	Sun, 05 Nov 2006 12:16:40 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Maurizio Lombardi <m.lombardi85@...il.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: New filesystem for Linux

Maurizio Lombardi wrote:
> On 11/4/06, Mikulas Patocka <mikulas@...ax.karlin.mff.cuni.cz> wrote:
> 
>> free space is organized in lists of free runs
>> and converted to bitmap only in case of
>> extreme fragmentation.
> 
> There is a performance reason to prefer lists of free blocks rather than 
> bitmap?
> 
> I read from [Tanenbaum: Operating System, Design and Implementation II
> ed. ] that lists are better than bitmap only when disk is almost full.
> 

Yes, if you have a truly random access medium.

If you have media like physical disks, where fragmentation costs you, 
the lists will kill you dead in no time at all.

	-hpa
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