Date: Fri, 30 May 2008 13:42:07 +0900 From: Pyun YongHyeon <pyunyh@gmail.com> To: Arnaud Houdelette <arnaud.houdelette@tzim.net> Cc: freebsd-stable@freebsd.org Subject: Re: Bad TCP performance with large MTU on 7-stable. Message-ID: <20080530044207.GH64177@cdnetworks.co.kr> In-Reply-To: <483EBCDD.2070408@tzim.net> References: <483EBCDD.2070408@tzim.net>
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On Thu, May 29, 2008 at 04:25:33PM +0200, Arnaud Houdelette wrote:
> 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@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 ?
>
It seems that handling jumbo frame in re(4) is one of trickiest
feature. Would you show me the following information?
- Captured tcpdump data on receiving side(i.e. host with re(4))
in your test.
- dmesg output of re(4)
- MTU size you've configured
- output of "netstat -nd -I re0"
- output of "ifconfig re0"
--
Regards,
Pyun YongHyeon
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