On Tue, 2007-07-03 at 22:20 -0400, jamal wrote: > On Tue, 2007-03-07 at 14:24 -0700, David Miller wrote: > [.. some useful stuff here deleted ..] > > > That's why you have to copy into a purpose-built set of memory > > that is composed of pages that _ONLY_ contain TX packet buffers > > and nothing else. > > > > The cost of going through the switch is too high, and the copies are > > necessary, so concentrate on allowing me to map the guest ports to the > > egress queues. Anything else is a waste of discussion time, I've been > > pouring over these issues endlessly for weeks, so if I'm saying doing > > copies and avoiding the switch is necessary I do in fact mean it. :-) > > ok, i get it Dave ;-> Thanks for your patience, that was useful. > Now that is clear for me, I will go back and look at your original email > and try to get back on track to what you really asked ;->
To expand on this, there are already "virtual" nic drivers in tree which do the demux based on dst mac and send to appropriate other guest (iseries_veth.c and Carsten Otte said the S/390 drivers do too). lguest and DaveM's LDOM make two more. There is currently no good way to write such a driver. If one recipient is full, you have to drop the packet: if you netif_stop_queue, it means a slow/buggy recipient blocks packets going to other recipients. But dropping packets makes networking suck. Some hypervisors (eg. Xen) only have a virtual NIC which is point-to-point: this sidesteps the issue, with the risk that you might need a huge number of virtual NICs if you wanted arbitrary guests to talk to each other (Xen doesn't support that, they route/bridge through dom0). Most hypervisors have a sensible maximum on the number of guests they could talk to, so I'm not too unhappy with a static number of queues. But the dstmac -> queue mapping changes in hypervisor-specific ways, so it really needs to be managed by the driver... Hope that adds something, Rusty. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
