On Sat, May 4, 2013 at 10:39 AM, Adrian Chadd <adr...@freebsd.org> wrote: > On 4 May 2013 06:52, Richard Sharpe <realrichardsha...@gmail.com> wrote: >> Hi folks, >> >> I understand better why I am seeing EINVAL intermittently when sending >> data from Samba via SMB2. >> >> The ixgbe driver, for TSO reasons, limits the amount of data that can >> be DMA'd to 65535 bytes. It returns EINVAL for any mbuf chain larger >> than that. >> >> The SO_SNDBUF for that socket is set to 131972. Mostly there is less >> than 64kiB of space available, so that is all TCP etc can put into the >> socket in one chain of mbufs. However, every now and then there is >> more than 65535 bytes available in the socket buffers, and we have an >> SMB packet that is larger than 65535 bytes, and we get hit. >> >> To confirm this I am going to set SO_SNDBUF back to the default of >> 65536 and test again. My repros are very reliable. >> >> However, I wondered if my only way around this if I want to continue >> to use SO_SNDBUF sizes larger than 65536 is to fragment large mbuf >> chains in the driver? > > Hm, is this is a problem without TSO?
We are using the card without TSO, so I am thinking of changing that limit to 131072 and retesting. I am currently testing with SO_SNDBUF=32768 and have not hit the problem. > Is the problem that the NIC can't handle a frame that big, or a buffer that > big? > Ie - if you handed the hardware two descriptors of 64k each, for the > same IP datagram, will it complain? I can't find any documentation, but it seems that with TSO it cannot handle a frame that big. Actually, since we are not using TSO, there really should not be a problem with larger frames. > Or do you need to break it up into two separate IP datagrams, facing > the driver, with a maximum size of 64k each? Not sure, but it looks like we need to do that. -- Regards, Richard Sharpe (何以解憂？唯有杜康。--曹操) _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
