Bad TCP performance with large MTU on 7-stable.

[Steven Hartland]

Does the trace show the window size being negotiated correctly?

----- Original Message ----- 
From: "Arnaud Houdelette" <arnaud.houdelette at tzim.net>


>I got really poor performance when I try to upload files to the box (via 
> pureFTP or Samba) when using jumbo frames somewhat  above  2k.
> 
> uname -a :
> FreeBSD carenath.tzim.net 7.0-STABLE FreeBSD 7.0-STABLE #4: Wed May 28 
> 17:45:14 CEST 2008     
> tzim at carenath.tzim.net:/usr/obj/usr/src/sys/CARENATH  amd64
> 
> It seems that TCP acks are delayed for about a second, so the upload 
> rate nevers goes above 60kB/s. I can provide wireshark captures done on 
> the box uploading the files if necessary.
> The client is a Windows XP64 box, but I do not recall having the same 
> problem on 6.2. I did got about 100 MB/s for similar file transfers, but 
> I had to disable jumbo frames when I upgraded to 7.0-Release because of 
> some bug on txcsum/rxcsum on re(4) so I only noticed the issue recently.
> 
> The txcsum bug doesn't seem to occur anymore, but now I have this 
> strange rate issue, with or without checksum offloading disabled.
> I also tried with tso disabled. Same results. Is it related to the re(4) 
> driver ? Or to the TCP stack ?


================================================
This e.mail is private and confidential between Multiplay (UK) Ltd. and the person or entity to whom it is addressed. In the event of misdirection, the recipient is prohibited from using, copying, printing or otherwise disseminating it or any information contained in it. 

In the event of misdirection, illegible or incomplete transmission please telephone +44 845 868 1337
or return the E.mail to postmaster at multiplay.co.uk.