diff options
| author | Jason Wang <jasowang@redhat.com> | 2011-06-10 04:56:17 +0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2011-06-12 02:57:47 +0400 |
| commit | 10a8d94a95742bb15b4e617ee9884bb4381362be (patch) | |
| tree | 768f2d92be0e12bca791bcb901ad4bdedc7d8a76 /drivers/net/tun.c | |
| parent | 40d15cd06e87722b1cc27d56c8274617580f2c56 (diff) | |
| download | linux-10a8d94a95742bb15b4e617ee9884bb4381362be.tar.xz | |
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/tun.c')
| -rw-r--r-- | drivers/net/tun.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/net/tun.c b/drivers/net/tun.c index ef68e13c042d..4dab85eecb60 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, |