Date: Wed, 26 Mar 2003 10:21:21 +0000 From: Ian Dowse <iedowse@maths.tcd.ie> To: Terry Lambert <tlambert2@mindspring.com> Cc: current@freebsd.org Subject: Re: NFS -current Message-ID: <200303261021.aa90692@salmon.maths.tcd.ie> In-Reply-To: Your message of "Tue, 25 Mar 2003 18:52:59 PST." <3E81160B.E5406C60@mindspring.com>
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In message <3E81160B.E5406C60@mindspring.com>, Terry Lambert writes: >Ian Dowse wrote: >> It is normal enough to get the above 'not responding' errors >> occasionally on a busy fileserver, but only if they are almost >> immediately followed by 'is alive again' messages. > >This is arguably a bug in the FreeBSD UDP packet reassembly code ... Actually, I was referring here to an effect that occurs when the time taken by the server to complete requests varies in a particular way. The NFS client may observe a large number of requests all answered within a few milliseconds, so it starts using short timeouts. Then for some reason (usually a long list of outstanding disk-intensive operations), the server takes a few seconds to complete the next request. Within this time, the client repeatedly times out, retransmits the request, backs off and repeats, and in extreme cases it is possible for the client to reach the limit that triggers the "not responding" warning. Ian
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