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Date: Fri, 14 Oct 2005 17:46:28 +0100
From: Brian Candler <B.Candler@pobox.com>
To: Eric Anderson <anderson@centtech.com>
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Cc: max@love2party.net, freebsd-current@freebsd.org,
	"M. Warner Losh" <imp@bsdimp.com>
Subject: Re: ufsstat - testers / feedback wanted!
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On Fri, Oct 14, 2005 at 11:20:02AM -0500, Eric Anderson wrote:
> For statistics gathering purposes though, should I worry about this, or 
> go for 'fast and imperfect' instead of 'perfect and slow'?  With 
> filesystems, I think it's more important to leave performance high and 
> get a notion of the statistics, rather than impact performance for 
> perfect stats (that you may only look at occasionally anyhow).

Losing the odd count probably isn't a problem, but I think there's the
possibility of a badly wrong value if you're updating a 64-bit word in two
halves. For example, it might be possible to wrap around from
00000000ffffffff to 0000000000000000 instead of 0000000100000000.