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SubjectRe: [2.6.30.1] Significant latency playing video file from NFS4 share
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On Tue, 2009-07-21 at 19:31 +0200, Frans Pop wrote:
> Any suggestions based on the data below?

Yeah. Sorry for the delay.

> Is the problem maybe that the amount of data transferred each time is so
> big that the network speed becomes a bottleneck and causes the latency?
> I can reproduce the issue with both a 10MBit wired link and with a 54MBit
> wireless link.
>
> Is this a kernel bug or a configuration issue?

<snip>

> elrond:/david mounted on /srv/fjp/david:
>
> op/s rpc bklog
> 0.80 0.00
> read: ops/s kB/s kB/op retrans avg RTT (ms) avg exe (ms)
> 0.750 192.196 256.262 0 (0.0%) 1998.933 1999.200
> write: ops/s kB/s kB/op retrans avg RTT (ms) avg exe (ms)
> 0.000 0.000 0.000 0 (0.0%) 0.000 0.000

This would be where you are losing your performance. 1998.933 ms rtt
means that you are seeing a 2 second delay from the instant the RPC
client pushes the request into the socket to the moment that socket
receives a reply from the server.

Basically, you have either a _very_ slow server, or (more likely) a
networking problem. A tcpdump ought to be able to show what the problem
is: whether it is the packets getting ACKed very slowly, and/or if you
have dropped packet issues or if it is truly a problem with the server
taking a long time to reply.

Cheers
Trond



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