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Date:      Wed, 18 Jul 2007 20:48:21 +0100 (BST)
From:      Robert Watson <rwatson@FreeBSD.org>
To:        Scott Bennett <bennett@cs.niu.edu>
Cc:        freebsd-net@freebsd.org, freebsd-current@freebsd.org, Max Laier <max@love2party.net>
Subject:   Re: Reminder: NET_NEEDS_GIANT, debug.mpsafenet going away in
Message-ID:  <20070718204552.G1096@fledge.watson.org>
In-Reply-To: <200707181807.l6II7twY010844@mp.cs.niu.edu>
References:  <200707181807.l6II7twY010844@mp.cs.niu.edu>

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On Wed, 18 Jul 2007, Scott Bennett wrote:

>  [Cc: list trimmed a bit more  --SB]
>     On Tue, 17 Jul 2007 23:42:14 +0200 Max Laier <max@love2party.net>
>
>> [ Excess CC-list ... testers needed!!! ]
>>
>> On Tuesday 17 July 2007, Robert Watson wrote:
>
>     I missed Robert Watson's start of thread, so I'm jumping in here
> with a question.
>
>>> This is a reminder e-mail that, in the very near future, Giant 
>>> compatibility shims for network protocols will be removed.
>
>     How, if at all, will this affect qemu users?  qemu exits unless AIO is 
> present in the kernel (or aio.ko has been kldload-ed).  In FreeBSD 6.2, AIO 
> results in a warning message at boot time that says AIO is not MPSAFE and 
> that therefore the networking stack will take a deep performance hit.

Per several earlier e-mails in the thread, AIO is MPSAFE in FreeBSD 7.0 and, 
as such, unaffected by this change.  As a result, I would expect that 
applications depending on AIO should now perform significantly better (but 
have done no measurement in this area).

Robert N M Watson
Computer Laboratory
University of Cambridge



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