* [PATCH] virtio_net: introduce VIRTIO_NET_HDR_F_DATA_VALID
@ 2011-06-10 10:56 Jason Wang
2011-06-10 11:28 ` Michael S. Tsirkin
0 siblings, 1 reply; 3+ messages in thread
From: Jason Wang @ 2011-06-10 10:56 UTC (permalink / raw)
To: rusty, mst, davem, netdev, linux-kernel, virtualization
Cc: yvugenfi, kvm, herbert, Jason Wang
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>
---
drivers/net/macvtap.c | 2 ++
drivers/net/tun.c | 2 ++
drivers/net/virtio_net.c | 2 ++
include/linux/virtio_net.h | 1 +
net/packet/af_packet.c | 2 ++
5 files changed, 9 insertions(+), 0 deletions(-)
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 74e9405..f43fa45 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -788,6 +788,8 @@ static __inline__ 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 c0c3cda..99ca471 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1681,6 +1681,8 @@ 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,
--
1.7.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] virtio_net: introduce VIRTIO_NET_HDR_F_DATA_VALID
2011-06-10 10:56 [PATCH] virtio_net: introduce VIRTIO_NET_HDR_F_DATA_VALID Jason Wang
@ 2011-06-10 11:28 ` Michael S. Tsirkin
2011-06-11 22:58 ` David Miller
0 siblings, 1 reply; 3+ messages in thread
From: Michael S. Tsirkin @ 2011-06-10 11:28 UTC (permalink / raw)
To: Jason Wang
Cc: rusty, davem, netdev, linux-kernel, virtualization, yvugenfi, kvm,
herbert
On Fri, Jun 10, 2011 at 06:56:17PM +0800, Jason Wang wrote:
> 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.
This wasn't required by the spec, but maybe it should be.
> 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>
> ---
> drivers/net/macvtap.c | 2 ++
> drivers/net/tun.c | 2 ++
> drivers/net/virtio_net.c | 2 ++
> include/linux/virtio_net.h | 1 +
> net/packet/af_packet.c | 2 ++
> 5 files changed, 9 insertions(+), 0 deletions(-)
>
> 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 74e9405..f43fa45 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -788,6 +788,8 @@ static __inline__ 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 c0c3cda..99ca471 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -1681,6 +1681,8 @@ 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,
> --
> 1.7.1
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] virtio_net: introduce VIRTIO_NET_HDR_F_DATA_VALID
2011-06-10 11:28 ` Michael S. Tsirkin
@ 2011-06-11 22:58 ` David Miller
0 siblings, 0 replies; 3+ messages in thread
From: David Miller @ 2011-06-11 22:58 UTC (permalink / raw)
To: mst
Cc: jasowang, rusty, netdev, linux-kernel, virtualization, yvugenfi,
kvm, herbert
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: Fri, 10 Jun 2011 14:28:28 +0300
> On Fri, Jun 10, 2011 at 06:56:17PM +0800, Jason Wang wrote:
>> 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.
>
> This wasn't required by the spec, but maybe it should be.
>
>> 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>
Applied to net-next-2.6
^ permalink raw reply [flat|nested] 3+ messages in thread
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2011-06-10 10:56 [PATCH] virtio_net: introduce VIRTIO_NET_HDR_F_DATA_VALID Jason Wang
2011-06-10 11:28 ` Michael S. Tsirkin
2011-06-11 22:58 ` David Miller
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