This patchset add supports for TX zero-copy between guest and host kernel through vhost. It significantly reduces CPU utilization on the local host on which the guest is located (It reduced 30-50% CPU usage for vhost thread for single stream test). The patchset is based on previous submission and comments from the community regarding when/how to handle guest kernel buffers to be released. This is the simplest approach I can think of after comparing with several other solutions. This patchset includes: 1. Induce a new sock zero-copy flag, SOCK_ZEROCOPY; 2. Induce a new device flag, NETIF_F_ZEROCOPY for device can support zero-copy; 3. Add a new struct skb_ubuf_info in skb_share_info for userspace buffers release callback when device DMA has done for that skb; 4. Add vhost zero-copy callback in vhost when skb last refcnt is gone; add vhost_zerocopy_add_used_and_signal to notify guest to release TX skb buffers. 5. Add macvtap zero-copy in lower device when sending packet is greater than 128 bytes. The patchset has passed netperf/netserver test on Chelsio, and continuing test on other 10GbE NICs, like Intel ixgbe, Mellanox mlx4... I will provide guest to host, host to guest performance data next week. However when running stress test, vhost & virtio_net seems out of sync, and virito_net interrupt was disabled somehow, and it stopped to send any packet. This problem has bothered me for a long long time, I will continue to look at this. Please review this. Thanks Shirley -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
