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





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