From 10a8d94a95742bb15b4e617ee9884bb4381362be Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Fri, 10 Jun 2011 00:56:17 +0000 Subject: virtio_net: introduce VIRTIO_NET_HDR_F_DATA_VALID There's no need for the guest to validate the checksum if it have been validated by host nics. So this patch introduces a new flag - VIRTIO_NET_HDR_F_DATA_VALID which is used to bypass the checksum examing in guest. The backend (tap/macvtap) may set this flag when met skbs with CHECKSUM_UNNECESSARY to save cpu utilization. No feature negotiation is needed as old driver just ignore this flag. Iperf shows 12%-30% performance improvement for UDP traffic. For TCP, when gro is on no difference as it produces skb with partial checksum. But when gro is disabled, 20% or even higher improvement could be measured by netperf. Signed-off-by: Jason Wang Acked-by: Michael S. Tsirkin Signed-off-by: David S. Miller diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index 6696e56..ecee0fe 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -508,6 +508,8 @@ static int macvtap_skb_to_vnet_hdr(const struct sk_buff *skb, vnet_hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM; vnet_hdr->csum_start = skb_checksum_start_offset(skb); vnet_hdr->csum_offset = skb->csum_offset; + } else if (skb->ip_summed == CHECKSUM_UNNECESSARY) { + vnet_hdr->flags = VIRTIO_NET_HDR_F_DATA_VALID; } /* else everything is zero */ return 0; diff --git a/drivers/net/tun.c b/drivers/net/tun.c index ef68e13..4dab85e 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -788,6 +788,8 @@ static ssize_t tun_put_user(struct tun_struct *tun, gso.flags = VIRTIO_NET_HDR_F_NEEDS_CSUM; gso.csum_start = skb_checksum_start_offset(skb); gso.csum_offset = skb->csum_offset; + } else if (skb->ip_summed == CHECKSUM_UNNECESSARY) { + gso.flags = VIRTIO_NET_HDR_F_DATA_VALID; } /* else everything is zero */ if (unlikely(memcpy_toiovecend(iv, (void *)&gso, total, diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index f685324..be3686a 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -274,6 +274,8 @@ static void receive_buf(struct net_device *dev, void *buf, unsigned int len) hdr->hdr.csum_start, hdr->hdr.csum_offset)) goto frame_err; + } else if (hdr->hdr.flags & VIRTIO_NET_HDR_F_DATA_VALID) { + skb->ip_summed = CHECKSUM_UNNECESSARY; } skb->protocol = eth_type_trans(skb, dev); diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h index 136040b..970d5a2 100644 --- a/include/linux/virtio_net.h +++ b/include/linux/virtio_net.h @@ -63,6 +63,7 @@ struct virtio_net_config { * specify GSO or CSUM features, you can simply ignore the header. */ struct virtio_net_hdr { #define VIRTIO_NET_HDR_F_NEEDS_CSUM 1 // Use csum_start, csum_offset +#define VIRTIO_NET_HDR_F_DATA_VALID 2 // Csum is valid __u8 flags; #define VIRTIO_NET_HDR_GSO_NONE 0 // Not a GSO frame #define VIRTIO_NET_HDR_GSO_TCPV4 1 // GSO frame, IPv4 TCP (TSO) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 67f6749..b54ec41 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1685,6 +1685,8 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock, vnet_hdr.flags = VIRTIO_NET_HDR_F_NEEDS_CSUM; vnet_hdr.csum_start = skb_checksum_start_offset(skb); vnet_hdr.csum_offset = skb->csum_offset; + } else if (skb->ip_summed == CHECKSUM_UNNECESSARY) { + vnet_hdr.flags = VIRTIO_NET_HDR_F_DATA_VALID; } /* else everything is zero */ err = memcpy_toiovec(msg->msg_iov, (void *)&vnet_hdr, -- cgit v0.10.2