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: 1/8: Add a new sock zero-copy flag, SOCK_ZEROCOPY; 2/8: Add a new device flag, NETIF_F_ZEROCOPY for lower level device support zero-copy; 3/8: Add a new struct skb_ubuf_info in skb_share_info for userspace buffers release callback when lower device DMA has done for that skb; 4/8: 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. 5/8: Add macvtap zero-copy in lower device when sending packet is greater than 128 bytes. 6/8: Add Chelsio 10Gb NIC to zero copy feature flag 7/8: Add Intel 10Gb NIC zero copy feature flag 8/8: Add Emulex 10Gb NIC zero copy feature flag The patchset is built against most recent linux 2.6.git. It has passed netperf/netserver multiple streams stress test on above NICs. The single stream test results from 2.6.37 kernel on Chelsio: 64K message size: copy_from_user dropped from 40% to 5%; vhost thread cpu utilization dropped from 76% to 28% I am collecting more test results against 2.6.39-rc3 kernel and will provide the test matrix later. 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
