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 <k...@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



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