Re: nfs performance: read only/gigE/nolock/1Tb per day

[Trond Myklebust <trond.myklebust@fys.uio.no>]

>>>>> " " == Bogdan Costescu <bogdan.costescu@iwr.uni-heidelberg.de> writes:

     > "max_interrupt_work" should not be modified unless a message
     > like "ethx: Too much work in interrupt!" is logged by the
     > kernel. In some cases, increasing "max_interrupt_work" without
     > also increasing the Rx ring size would not help...

So what would an avalanche of ICMP Time Exceeded messages usually
indicate as far as the driver/card is concerned?

At the networking levels, a single Time Exceeded message means that
some fragment(s) got dropped and/or lost, so some datagram never got
reassembled within /proc/sys/net/ipv4/ipfrag_low_thresh seconds
(as per RFC1122).

In the avalanching case that I've sometimes observed, then it looks as
if *no* datagrams are getting rebuilt.
IOW: the client is just sitting there sending off ICMP messages, and
never reading the reply. Changing card/driver did not help in the
cases I observed, but shutting down the network, and then bringing it
up again sometimes did. Any suggestions?

Cheers,
  Trond

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