Date: Fri, 13 Jan 2012 09:58:58 -0800 From: Jack Vogel <jfvogel@gmail.com> To: Iordan Iordanov <iordan@cdf.toronto.edu> Cc: freebsd-bugs@freebsd.org, CDF Admin <admin@cdf.toronto.edu> Subject: Re: unable to set mtu 9000 on Intel x520-t2 adapter Message-ID: <CAFOYbcnRc-K=dkym09eY%2BSk831%2BUhf==oGwWzHAmf82gy%2B5_gw@mail.gmail.com> In-Reply-To: <4F106861.80507@cdf.toronto.edu> References: <4F106861.80507@cdf.toronto.edu>
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Its a system resource thing, when you increase to a 9K mtu the driver will use 9K mbuf clusters, and with the queues and rings you have its unable to get enough. Very important to look at kern.ipc.nbm* In your case nmbjumbo9 is the pool, if you had 4K it would those clusters. Change the defaults in /etc/sysctl.conf. Cheers, Jack On Fri, Jan 13, 2012 at 9:22 AM, Iordan Iordanov <iordan@cdf.toronto.edu>wrote: > Hello, > > We are testing FreeBSD 9.0-RELEASE on a pair of machines with 10GBASE-T > Intel x520-t2 adapters interconnected with a straight-through cat6 rj45 > cable. With mtu 1500, we are achieving aproximately 4 gigabits/s both > directions as demonstrated with iperf. We wanted to test with mtu 9000 to > see whether there would be any difference, but we encountered a problem > setting it. We ran the following commands to alter the MTU to 9000 on the > two machines (fw3 and fw4): > > fw3# ifconfig ix1 192.168.1.100 mtu 9000 > fw4# ifconfig ix1 192.168.1.200 mtu 9000 > > However, instead of getting mtu set to 9000, what we see is the following > message in the kernel output of both machines: > > ix1: Could not setup receive structures > ix1: Could not setup receive structures > > and no traffic getting through. The moment we run: > > fw3# ifconfig ix1 192.168.1.100 mtu 1500 > fw4# ifconfig ix1 192.168.1.200 mtu 1500 > > we see: > > ix1: link state changed to DOWN > ix1: link state changed to UP > > and traffic starts getting through as before. More information about our > hardware is: > > Motherboard: Supermicro H8DGU-F > CPU: AMD 6128 8-core > Memory: 16GB DDR3 > NICs: Intel x520-t2 10GbaseT adapters > > An ifconfig ix1 output for one of the machines: > > fw4# ifconfig ix1 > ix1: flags=8843<UP,BROADCAST,**RUNNING,SIMPLEX,MULTICAST> metric 0 mtu > 1500 > > options=401bb<RXCSUM,TXCSUM,**VLAN_MTU,VLAN_HWTAGGING,JUMBO_** > MTU,VLAN_HWCSUM,TSO4,VLAN_**HWTSO> > ether 00:1b:21:d6:19:51 > inet 192.168.1.200 netmask 0xffffff00 broadcast 192.168.1.255 > nd6 options=29<PERFORMNUD,**IFDISABLED,AUTO_LINKLOCAL> > media: Ethernet autoselect (autoselect <full-duplex>) > status: active > > > Many thanks for any help/action on this! > > Sincerely, > > Iordan Iordanov > CDF System Administrator > University of Toronto > ______________________________**_________________ > freebsd-bugs@freebsd.org mailing list > http://lists.freebsd.org/**mailman/listinfo/freebsd-bugs<http://lists.freebsd.org/mailman/listinfo/freebsd-bugs>; > To unsubscribe, send any mail to "freebsd-bugs-unsubscribe@**freebsd.org<freebsd-bugs-unsubscribe@freebsd.org> > " >
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