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Date: Tue, 25 Jul 2006 11:09:43 +0100
From: "Peter Edwards" <peadar.edwards@gmail.com>
To: "Jim Rees" <rees@umich.edu>
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References: <200607241456.KAA63411@snowhite.cis.uoguelph.ca>
	<20060724152823.C32D81BB93@citi.umich.edu>
Cc: fs@freebsd.org, rick@snowhite.cis.uoguelph.ca
Subject: Re: freebsd4.11 patch for nfs over tcp
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On 7/24/06, Jim Rees <rees@umich.edu> wrote:
> Delayed acks when properly implemented should not cause a performance hit.
> The problem is that there are many buggy implementations.  If you have to
> turn off delayed acks to get good nfs performance, then there is a bug in
> the tcp stack.  See, for example, rfc 2525 page 40, "Stretch ACK violation."
> MacOS has this same problem.
>

"NODELAY" is to turn of the Nagle algorithm, not delayed acks, and
Nagle can interact badly with delayed acks on the peer for some
workloads/protocols. I'm not sure NFS is one of those cases, but I
suspect it probably is.