linux-kernel - Re: vfat file system extreme fragmentation on multiprocessor

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Message-ID: <20080911210908.GC31271@csclub.uwaterloo.ca>
Date:	Thu, 11 Sep 2008 17:09:08 -0400
From:	lsorense@...lub.uwaterloo.ca (Lennart Sorensen)
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Harun Scheutzow <harun04@...eutzow.de>,
	linux-kernel@...r.kernel.org
Subject: Re: vfat file system extreme fragmentation on multiprocessor

On Thu, Sep 11, 2008 at 12:36:24PM -0700, H. Peter Anvin wrote:
> Lennart Sorensen wrote:
> >
> >I don't think fat filesystems have any concept of reserving space for
> >expanding files.  It's a pretty simple filesystem after all designed for
> >a single cpu machine with a non-multitasking OS (if you can call DOS an
> >OS).  Space tends to be allocated from the start of the disk wherever
> >free space is found since otherwise you would have to go searching for
> >the free space, which isn't that efficient.
> >
> 
> Well, you can always do that in-memory.

It still involves searching no matter where you do it.  With FAT-16 that
means up to 2^16 clusters to search through.  With FAT-32 even more.  It
doesn't have a cluster bitmap to speed things up.

-- 
Len Sorensen
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