Andrew Gallatin wrote: > > For the case where the mtu is larger than MCLBYTES (2048), FreeBSD's > TCP implementation restricts the mss to a multiple of MCLBYTES. This > appears to have been inherited from 4.4BSD-lite. > > On adapters with 9000 byte jumbo frames, this limits the mss to 8192 > bytes, and wastes nearly 1KB out of each frame. This is especially > annoying because many drivers for adapters which support 9000 byte mtus > allocate their own 9000 byte receive buffers and don't even use mbufs > which are MCLBYTES in length. In this case, the mss restriction guarantees > a nearly 1000 byte wastage per frame.
When I was implementing the tcp_hostcache I reorganized/redid the tcp_mss() function and wondered about that too. I don't know if this rounding to MCLBYTES is still the right thing to do. > Would it be OK if I made this code optional via a sysctl? Could you run some bechmarks with the current MCLBYTES rounding and without it on 100Mbit 1.5kMTU and GigE with 9k MTU? -- Andre _______________________________________________ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "[EMAIL PROTECTED]"
