Date: Fri, 9 Apr 2004 13:31:45 -0700 From: Mike Hunter <mhunter@berkeley.edu> To: freebsd-net@freebsd.org Subject: Re: Broadcom BCM5788 jumbo frames? (FBSD 5.2.1) Message-ID: <20040409203145.GC8722@ack.Berkeley.EDU> In-Reply-To: <20040406180020.GA21071@ack.Berkeley.EDU> References: <20040406180020.GA21071@ack.Berkeley.EDU>
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On Apr 06, "To freebsd-net@freebsd.org" wrote: > Hi, > > I have a Broadcom BCM5788 card that I'd like to use with jumboframes, but > it seems that the card (or the driver) only allows a max of 1500 MTU. > > ifconfig bge0 mtu 9000 > ifconfig: ioctl (set mtu): Invalid argument > > 1500 and less works. > > I had this problem with my BCM5707M, and lo and behold if you look in > if_bge.c it says it can't do it, but I looked and I can't find a similar > comment for the BCM5788. > > Any thoughts? The system in question is 5.2.1-RELEASE-p3. The bge card > is builtin to the motherboard (shuttle sb75g2 on 64 bit pci.) > > While I have everybody's attention, what's a reasonable goal for > throughput between two of these cards? I broke through the 33mhz pci > barrier and am now getting iperf results of: > > [ 6] 0.0-10.0 sec 535 MBytes 449 Mbits/sec > > ( Obviously, without jumbo frames.) > > I've increased the tcp send and recv space....Any other suggestions? I received this off-list: There's nothing to think about: Broadcom NICs based on the 5705 ASIC do not support jumbo frames. You did not bother to provide the dmesg output from your system, so I can't see the ASIC rev from the probe message, but I'm pretty sure it's in the 5705 family. Compare the output against the ASIC revision listing in if_bgereg.h. There's no driver jiggling involved: the hardware just won't do what you're trying to do. As far as expected performance goes, if you actually have a 64-bit NIC (or a 32-bit/66Mhz NIC), you should be able to reach 900Mbps speeds with TCP, although your chances of achieving this are better if you have checksum offload capability. Mike
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