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Date: Fri, 18 Oct 2002 07:55:55 +1000
From: Nathan Scott <nathans@sgi.com>
To: Andreas Gruenbacher <agruen@suse.de>
Cc: "Theodore Ts'o" <tytso@mit.edu>, Christoph Hellwig <hch@infradead.org>,
       torvalds@transmeta.com, Andrew Morton <akpm@digeo.com>,
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Subject: Re: [PATCH 1/5] Add POSIX Access Control Lists to ext2/3
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On Thu, Oct 17, 2002 at 12:04:08PM +0200, Andreas Gruenbacher wrote:
> Hello Nathan,

hi there,

> On Thursday 17 October 2002 00:48, Nathan Scott wrote:
> > They are an optimisization for the one special case (posix acls),
> > and manage to pollute the VFS for that one special case ...
> ...
> As soon as any filesystem independent part of the kernel needs an interface 
> more efficient that pass-by-value we will again have exactly the same 
> problem.

My point is simply that a proposal to extend the VFS in this way needs
to be accompanied by a compelling argument showing the performance bump
that its providing.

> Going to disk and fetching EAs only causes disk accesses once; afterwards the 
> block is cached.

Good - this is true for both XFS and ext2/3 then.  So, we are talking about
using ref counting vs. copying for any in-kernel users of attrs, and you're
saying there is some significant overheads with copying and I'm saying show
me what kind of overheads we're talking about, please.

cheers.

-- 
Nathan
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