[PATCH V2 net-next 1/1] hv_netvsc: Use the xmit_more skb flag to optimize signaling the host

[PATCH V2 net-next 1/1] hv_netvsc: Use the xmit_more skb flag to optimize signaling the host

[K. Y. Srinivasan]

Based on the information given to this driver (via the xmit_more skb flag),
we can defer signaling the host if more packets are on the way. This will help
make the host more efficient since it can potentially process a larger batch of
packets. Implement this optimization.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
	v2: Fixed up indentation based on feedback from David Miller.

 drivers/net/hyperv/netvsc.c |   20 ++++++++++++--------
 1 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 2e8ad06..5fdc5e1 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -743,6 +743,7 @@ static inline int netvsc_send_pkt(
 	u64 req_id;
 	int ret;
 	struct hv_page_buffer *pgbuf;
+	u32 vmbus_flags = VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED;
 
 	nvmsg.hdr.msg_type = NVSP_MSG1_TYPE_SEND_RNDIS_PKT;
 	if (packet->is_data_pkt) {
@@ -772,19 +773,22 @@ static inline int netvsc_send_pkt(
 	if (packet->page_buf_cnt) {
 		pgbuf = packet->cp_partial ? packet->page_buf +
 			packet->rmsg_pgcnt : packet->page_buf;
-		ret = vmbus_sendpacket_pagebuffer(out_channel,
-						  pgbuf,
-						  packet->page_buf_cnt,
-						  &nvmsg,
-						  sizeof(struct nvsp_message),
-						  req_id);
+		ret = vmbus_sendpacket_pagebuffer_ctl(out_channel,
+						      pgbuf,
+						      packet->page_buf_cnt,
+						      &nvmsg,
+						      sizeof(struct
+							     nvsp_message),
+						      req_id,
+						      vmbus_flags,
+						      !packet->xmit_more);
 	} else {
-		ret = vmbus_sendpacket(
+		ret = vmbus_sendpacket_ctl(
 				out_channel, &nvmsg,
 				sizeof(struct nvsp_message),
 				req_id,
 				VM_PKT_DATA_INBAND,
-				VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+				vmbus_flags, !packet->xmit_more);
 	}
 
 	if (ret == 0) {
-- 
1.7.4.1

Re: [PATCH V2 net-next 1/1] hv_netvsc: Use the xmit_more skb flag to optimize signaling the host

[Eric Dumazet]

On Thu, 2015-04-30 at 16:29 -0700, K. Y. Srinivasan wrote:
> Based on the information given to this driver (via the xmit_more skb flag),
> we can defer signaling the host if more packets are on the way. This will help
> make the host more efficient since it can potentially process a larger batch of
> packets. Implement this optimization.
> 
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> ---
> 	v2: Fixed up indentation based on feedback from David Miller.
> 
>  drivers/net/hyperv/netvsc.c |   20 ++++++++++++--------
>  1 files changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index 2e8ad06..5fdc5e1 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -743,6 +743,7 @@ static inline int netvsc_send_pkt(
>  	u64 req_id;
>  	int ret;
>  	struct hv_page_buffer *pgbuf;
> +	u32 vmbus_flags = VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED;
>  
>  	nvmsg.hdr.msg_type = NVSP_MSG1_TYPE_SEND_RNDIS_PKT;
>  	if (packet->is_data_pkt) {
> @@ -772,19 +773,22 @@ static inline int netvsc_send_pkt(
>  	if (packet->page_buf_cnt) {
>  		pgbuf = packet->cp_partial ? packet->page_buf +
>  			packet->rmsg_pgcnt : packet->page_buf;
> -		ret = vmbus_sendpacket_pagebuffer(out_channel,
> -						  pgbuf,
> -						  packet->page_buf_cnt,
> -						  &nvmsg,
> -						  sizeof(struct nvsp_message),
> -						  req_id);
> +		ret = vmbus_sendpacket_pagebuffer_ctl(out_channel,
> +						      pgbuf,
> +						      packet->page_buf_cnt,
> +						      &nvmsg,
> +						      sizeof(struct
> +							     nvsp_message),
> +						      req_id,
> +						      vmbus_flags,
> +						      !packet->xmit_more);
>  	} else {
> -		ret = vmbus_sendpacket(
> +		ret = vmbus_sendpacket_ctl(
>  				out_channel, &nvmsg,
>  				sizeof(struct nvsp_message),
>  				req_id,
>  				VM_PKT_DATA_INBAND,
> -				VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> +				vmbus_flags, !packet->xmit_more);
>  	}
>  
>  	if (ret == 0) {

This might be problematic, if queue is stopped ( netif_tx_stop_queue())

You need to force a kick if we are about to stop the queue :

Random example : commit ddd0ca5d60b350bbfbfb60b25885a9779ce6d6c7

RE: [PATCH V2 net-next 1/1] hv_netvsc: Use the xmit_more skb flag to optimize signaling the host

[KY Srinivasan]

> -----Original Message-----
> From: Eric Dumazet [mailto:eric.dumazet@gmail.com]
> Sent: Thursday, April 30, 2015 9:37 PM
> To: KY Srinivasan
> Cc: davem@davemloft.net; netdev@vger.kernel.org; linux-
> kernel@vger.kernel.org; devel@linuxdriverproject.org; olaf@aepfle.de;
> apw@canonical.com; jasowang@redhat.com
> Subject: Re: [PATCH V2 net-next 1/1] hv_netvsc: Use the xmit_more skb flag
> to optimize signaling the host
> 
> On Thu, 2015-04-30 at 16:29 -0700, K. Y. Srinivasan wrote:
> > Based on the information given to this driver (via the xmit_more skb flag),
> > we can defer signaling the host if more packets are on the way. This will
> help
> > make the host more efficient since it can potentially process a larger batch
> of
> > packets. Implement this optimization.
> >
> > Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> > ---
> > 	v2: Fixed up indentation based on feedback from David Miller.
> >
> >  drivers/net/hyperv/netvsc.c |   20 ++++++++++++--------
> >  1 files changed, 12 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> > index 2e8ad06..5fdc5e1 100644
> > --- a/drivers/net/hyperv/netvsc.c
> > +++ b/drivers/net/hyperv/netvsc.c
> > @@ -743,6 +743,7 @@ static inline int netvsc_send_pkt(
> >  	u64 req_id;
> >  	int ret;
> >  	struct hv_page_buffer *pgbuf;
> > +	u32 vmbus_flags =
> VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED;
> >
> >  	nvmsg.hdr.msg_type = NVSP_MSG1_TYPE_SEND_RNDIS_PKT;
> >  	if (packet->is_data_pkt) {
> > @@ -772,19 +773,22 @@ static inline int netvsc_send_pkt(
> >  	if (packet->page_buf_cnt) {
> >  		pgbuf = packet->cp_partial ? packet->page_buf +
> >  			packet->rmsg_pgcnt : packet->page_buf;
> > -		ret = vmbus_sendpacket_pagebuffer(out_channel,
> > -						  pgbuf,
> > -						  packet->page_buf_cnt,
> > -						  &nvmsg,
> > -						  sizeof(struct
> nvsp_message),
> > -						  req_id);
> > +		ret = vmbus_sendpacket_pagebuffer_ctl(out_channel,
> > +						      pgbuf,
> > +						      packet->page_buf_cnt,
> > +						      &nvmsg,
> > +						      sizeof(struct
> > +							     nvsp_message),
> > +						      req_id,
> > +						      vmbus_flags,
> > +						      !packet->xmit_more);
> >  	} else {
> > -		ret = vmbus_sendpacket(
> > +		ret = vmbus_sendpacket_ctl(
> >  				out_channel, &nvmsg,
> >  				sizeof(struct nvsp_message),
> >  				req_id,
> >  				VM_PKT_DATA_INBAND,
> > -
> 	VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> > +				vmbus_flags, !packet->xmit_more);
> >  	}
> >
> >  	if (ret == 0) {
> 
> This might be problematic, if queue is stopped ( netif_tx_stop_queue())
> 
> You need to force a kick if we are about to stop the queue :
> 
> Random example : commit ddd0ca5d60b350bbfbfb60b25885a9779ce6d6c7

Thanks Eric; I will fix and resend.

Regards,

K. Y
> 
>