From: Trond Myklebust <trond.myklebust@fys.uio.no>
Subject: Re: [RFC,PATCH 11/15] knfsd: RDMA transport core
Date: Wed, 23 May 2007 11:37:19 -0400
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Cc: Tom Talpey <Thomas.Talpey@netapp.com>, Greg Banks <gnb@sgi.com>,
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On Wed, 2007-05-23 at 10:12 -0500, Tom Tucker wrote:
> Ah, this is a very good point. So then I think we need a transport
> specific deferral mechanism. 

No. I'm not sure that justifies a transport specific mechanism. It
rather calls for a more clever algorithm for deferring. Both NFSv3 and
NFSv4 have generic error messages that state 'I'm busy now, please try
again later'. As I said earlier, returning those errors are inevitably
more efficient than dropping.
Even for NFSv3 over TCP, dropping a single WRITE request will typically
cause a 60 second flat holdup instead of the more desirable retry +
exponential backoff.

Trond


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