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 <jasowang@redhat.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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40d15cd06e
Коммит
10a8d94a95
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@ -508,6 +508,8 @@ static int macvtap_skb_to_vnet_hdr(const struct sk_buff *skb,
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vnet_hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
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vnet_hdr->csum_start = skb_checksum_start_offset(skb);
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vnet_hdr->csum_offset = skb->csum_offset;
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} else if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
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vnet_hdr->flags = VIRTIO_NET_HDR_F_DATA_VALID;
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} /* else everything is zero */
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return 0;
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@ -788,6 +788,8 @@ static ssize_t tun_put_user(struct tun_struct *tun,
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gso.flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
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gso.csum_start = skb_checksum_start_offset(skb);
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gso.csum_offset = skb->csum_offset;
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} else if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
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gso.flags = VIRTIO_NET_HDR_F_DATA_VALID;
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} /* else everything is zero */
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if (unlikely(memcpy_toiovecend(iv, (void *)&gso, total,
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@ -274,6 +274,8 @@ static void receive_buf(struct net_device *dev, void *buf, unsigned int len)
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hdr->hdr.csum_start,
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hdr->hdr.csum_offset))
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goto frame_err;
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} else if (hdr->hdr.flags & VIRTIO_NET_HDR_F_DATA_VALID) {
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skb->ip_summed = CHECKSUM_UNNECESSARY;
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}
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skb->protocol = eth_type_trans(skb, dev);
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@ -63,6 +63,7 @@ struct virtio_net_config {
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* specify GSO or CSUM features, you can simply ignore the header. */
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struct virtio_net_hdr {
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#define VIRTIO_NET_HDR_F_NEEDS_CSUM 1 // Use csum_start, csum_offset
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#define VIRTIO_NET_HDR_F_DATA_VALID 2 // Csum is valid
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__u8 flags;
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#define VIRTIO_NET_HDR_GSO_NONE 0 // Not a GSO frame
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#define VIRTIO_NET_HDR_GSO_TCPV4 1 // GSO frame, IPv4 TCP (TSO)
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@ -1685,6 +1685,8 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
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vnet_hdr.flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
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vnet_hdr.csum_start = skb_checksum_start_offset(skb);
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vnet_hdr.csum_offset = skb->csum_offset;
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} else if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
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vnet_hdr.flags = VIRTIO_NET_HDR_F_DATA_VALID;
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} /* else everything is zero */
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err = memcpy_toiovec(msg->msg_iov, (void *)&vnet_hdr,
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