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| author | Jason Wang <jasowang@redhat.com> | 2011-06-10 00:56:17 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2011-06-11 15:57:47 -0700 |
| commit | 10a8d94a95742bb15b4e617ee9884bb4381362be (patch) | |
| tree | 768f2d92be0e12bca791bcb901ad4bdedc7d8a76 /drivers/net/macvtap.c | |
| parent | 40d15cd06e87722b1cc27d56c8274617580f2c56 (diff) | |
| download | lwn-10a8d94a95742bb15b4e617ee9884bb4381362be.tar.gz lwn-10a8d94a95742bb15b4e617ee9884bb4381362be.zip | |
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>
Diffstat (limited to 'drivers/net/macvtap.c')
| -rw-r--r-- | drivers/net/macvtap.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index 6696e56e6320..ecee0fe65a97 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; |