Guest virtio_net receives packets from its pre-allocated vring buffers, then it delivers these packets to upper layer protocols as skb buffs. So it's not necessary to pre-allocate skb for each mergable buffer, then frees it when it's useless. This patch has deferred skb allocation when receiving packets for both big packets and mergeable buffers. It reduces skb pre-allocations and skb_frees. Based on Mickael & Avi's suggestion. A destroy function has been created to push virtio free buffs to vring for unused pages, and used page private to maintain page list. I didn't touch small packet skb allocation to avoid extra copies for small packets. This patch has tested and measured against 2.6.32-rc5 git. It is built again 2.6.32-rc7 kernel. Tests have been done for small packets, big packets and mergeable buffers. The single netperf TCP_STREAM performance improved for host to guest. It also reduces UDP packets drop rate. The netperf laptop results were: mtu=1500 netperf -H xxx -l 120 w/o patch w/i patch (two runs) guest to host: 3336.84Mb/s 3730.14Mb/s ~ 3582.88Mb/s host to guest: 3165.10Mb/s 3370.39Mb/s ~ 3407.96Mb/s -- 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
