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From: Daniel Phillips <phillips@arcor.de>
To: Chris Friesen <cfriesen@nortelnetworks.com>,
       Andrew Morton <akpm@digeo.com>
Subject: Re: The reason to call it 3.0 is the desktop (was Re: [OT] 2.6 not 3.0 -  (NUMA))
Date: Mon, 7 Oct 2002 21:21:28 +0200
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Cc: "Martin J. Bligh" <mbligh@aracnet.com>, Oliver Neukum <oliver@neukum.name>,
       Rob Landley <landley@trommello.org>,
       Linus Torvalds <torvalds@transmeta.com>, linux-kernel@vger.kernel.org
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On Monday 07 October 2002 20:58, Chris Friesen wrote:
> Andrew Morton wrote:
> 
> > Go into ext2_new_inode, replace the call to find_group_dir with
> > find_group_other.  Then untar a kernel tree, unmount the fs,
> > remount it and see how long it takes to do a
> > 
> > 	`find . -type f  xargs cat > /dev/null'
> > 
> > on that tree.  If your disk is like my disk, you will achieve
> > full disk bandwidth.
> 
> Pardon my ignorance, but what's the difference between find_group_dir 
> and find_group_other, and why aren't we using find_group_other already 
> if its so much faster?

These are the heuristics that determine where in the volume directory
inodes are allocated:

   http://lxr.linux.no/source/fs/ext2/ialloc.c#L221

Ext2 likes to spread directory inodes around the volume so that there is
room to keep the associated file blocks nearby.  This interacts rather
poorly with readahead.

-- 
Daniel
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