slowdowns with MTU > 8k

Greg Dickie greg at
Thu Jul 26 11:59:13 GMT 2001

Hi Chris,

I don't think so, so what I just posted. We can do a ping of 9014 and this MTU
is supposed to be supported by the switch and all the other NICs. Every other
test we do we see a benefit in the bigger MTU, it just seems like a samba
specific thing. I just responded to a post by Anton because from some tests I
did yesterday it appears to be sendfile related....

Thanks for the reponse though it was a good idea,

On 25-Jul-01 Christopher R. Hertel wrote:
> Is it just Samba?
> I'm wondering if some device (your GIGE interface card, some intermediate 
> switch, something) has a lower limit and could be splitting your packets 
> in half on you.  That would slow things down a bit.
> Chris -)-----
>> Hi,
>>   We are playing with gigabit ethernet and we get quite good performance
>> when the MTU is set around 8k. If we set it at 9014 (max MTU on the switch
>> we use) the throughput from samba gets cut in half. Tried playing with
>> "max xmit" but no effect.
>>   Anyone have any ideas what the problem could be or have any tools to
>> dump the profile shared memory?
>> Thanks,
>> Greg
>> ---------------------------------------------------------------------
>> Greg Dickie
>> just a guy
>> greg at
> -- 
> Christopher R. Hertel -)-----                   University of Minnesota
> crh at              Networking and Telecommunications Services
>     Ideals are like stars; you will not succeed in touching them
>     with your choose them as your guides, and following
>     them you will reach your destiny.  --Carl Schultz

Greg Dickie
just a guy
greg at

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