On 3/14/07, Michael S. Tsirkin <[EMAIL PROTECTED]> wrote:
> Quoting Moni Levy <[EMAIL PROTECTED]>:
> Subject: Re: [ofa-general] [Bug 450] New: IPoIB BW drop (measured with iperf)
with mtu=1500 on x86 RH4UP3
>
> On 3/13/07, Michael S. Tsirkin <[EMAIL PROTECTED]> wrote:
> >> >Why are you playing with ifc mtu?
> >>
> >> We needed to do some IP forwarding tests between IB and Ethernet and
> >> wanted to have the same MTU for the eth0 and ib0 interfaces, after
> >> that we reproduced that in a peer to peer configuration.
> >
> >OK but PMTU discovery would do this better, won't it?
>
> I'm not sure (it will probably drop some packets at the beginning).
Can you check pls?
> Anyway lower MTU should work.
Manually tweaking MTU seems to be broken in lots of systems -
I sometimes see the same behaviour with gigabit ethernet.
> >As a side note, with 1.5K MTU it's probably better to use datagram mode
> >anyway.
>
> Now I see that I missed that in the report. We used datagram mode.
Did you try checking ethernet BW on the same machine?
Ethernet seem to work fine.
I can't reproduce the bug in the last week. The only thing that I see
now is that at that same MTU and connected mode enabled I get the same
low BW. What version of tcpdump are You using ?
-- Moni
--
MST
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