On Fri, Apr 24, 2015 at 9:12 AM, Luke Gorrie <luke@xxxxxxxx> wrote: > - How fast would the new design likely be? This proposal eliminates two things in the path: 1. Compared to vhost_net, it bypasses the host tun driver and network stack, replacing it with direct vhost_net <-> vhost_net data transfer. At this level it's compared to vhost-user, but it's not programmable in userspace! 2. Data copies are eliminated because the Shared Buffers BAR gives both VMs access to the packets. My concern is the overhead of the vhost_net component copying descriptors between NICs. In a 100% shared memory model, each VM only has a receive queue that the other VM places packets into. There are no tx queues. The notification mechanism is an event fd that is ioeventfd for VM1 and irqfd for VM2. In other words, when VM1 kicks the queue, VM2 receives an interrupt (of course polling the receive queue is also possible). It would be interesting to compare the two approaches. > Our recent experience in Snabb Switch land is that networking on x86 is now > more of a HPC problem than a system programming problem. The SIMD bandwidth > per core keeps increasing that this erodes the value of traditional (and > complex) system programming optimizations. I will be interested to compare > notes with others on this, already on Haswell but more so when we have > AVX512. > > Incidentally, we also did a pile of work last year on zero-copy NIC->VM > transfers and discovered a lot of interesting problems and edge cases where > Virtio-net spec and/or drivers are hard to match up with common NICs. Happy > to explain a bit about our experience if that would be valuable. That sounds interesting, can you describe the setup? Stefan _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
