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SubjectRe: bizarre network timing problem
Felix von Leitner wrote:
> Thus spake Rick Jones (rick.jones2@hp.com):
>
>>>Oh I'm pretty sure it's not my application, because my application performs
>>>well over ethernet, which is after all its purpose. Also I see the
>>>write, the TCP uncork, then a pause, and then the packet leaving.
>>
>>Well, a wise old engineer tried to teach me that the proper spelling is
>>ass-u-me :) so just for grins, you might try the TCP_RR test anyway :) And
>>even if your application is correct (although I wonder why the receiver
>>isn't sucking data-out very quickly...) if you can reproduce the problem
>>with netperf it will be easier for others to do so.
>
>
> My application is only the server, the receiver is smbget from Samba, so
> I don't feel responsible for it :-)

Might want to strace it anyway... no good deed (such as reporting a potential
issue) goes unpunished :)

> Still, when run over Ethernet, it works fine without waiting for
> timeouts to expire.

Past performance is no guarantee of current correctness :) And over an
Ethernet, there will be a very different set of both timings and TCP segment
sizes compared to loopback.

My guess is that you will find setting the lo mtu to 1500 a very interesting
experiment.

>
> To reproduce this:
>
> - smbget is from samba, you probably already have this
> - gatling (my server) can be gotten from
> cvs -d :pserver:cvs@cvs.fefe.de:/cvs -z9 co dietlibc libowfat gatling
>
> dietlibc is not strictly needed, but it's my environment.
> First built dietlibc, then libowfat, then gatling.
>
> Felix

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