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Subject[PATCH V6 net-next 1/1] hv_netvsc: Use the xmit_more skb flag to optimize signaling the host
Date
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.
v3,v4: If the queue could be stopped, deal with that condition: Eric Dumazet <eric.dumazet@gmail.com>
v5: Fixed up indentation based on feedback from David Miller.
V6: Fixed additional indentation/formatting: Joe Perches <joe@perches.com>

drivers/net/hyperv/netvsc.c | 43 +++++++++++++++++++++++++++----------------
1 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index ea091bc..b024968 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 ring_avail = hv_ringbuf_avail_percent(&out_channel->outbound);

nvmsg.hdr.msg_type = NVSP_MSG1_TYPE_SEND_RNDIS_PKT;
if (packet->is_data_pkt) {
@@ -769,32 +770,42 @@ static inline int netvsc_send_pkt(
if (out_channel->rescind)
return -ENODEV;

+ /*
+ * It is possible that once we successfully place this packet
+ * on the ringbuffer, we may stop the queue. In that case, we want
+ * to notify the host independent of the xmit_more flag. We don't
+ * need to be precise here; in the worst case we may signal the host
+ * unnecessarily.
+ */
+ if (ring_avail < (RING_AVAIL_PERCENT_LOWATER + 1))
+ packet->xmit_more = false;
+
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_DATA_PACKET_FLAG_COMPLETION_REQUESTED,
+ !packet->xmit_more);
} else {
- ret = vmbus_sendpacket(
- out_channel, &nvmsg,
- sizeof(struct nvsp_message),
- req_id,
- VM_PKT_DATA_INBAND,
- VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+ ret = vmbus_sendpacket_ctl(out_channel, &nvmsg,
+ sizeof(struct nvsp_message),
+ req_id,
+ VM_PKT_DATA_INBAND,
+ VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED,
+ !packet->xmit_more);
}

if (ret == 0) {
atomic_inc(&net_device->num_outstanding_sends);
atomic_inc(&net_device->queue_sends[q_idx]);

- if (hv_ringbuf_avail_percent(&out_channel->outbound) <
- RING_AVAIL_PERCENT_LOWATER) {
- netif_tx_stop_queue(netdev_get_tx_queue(
- ndev, q_idx));
+ if (ring_avail < RING_AVAIL_PERCENT_LOWATER) {
+ netif_tx_stop_queue(netdev_get_tx_queue(ndev, q_idx));

if (atomic_read(&net_device->
queue_sends[q_idx]) < 1)
--
1.7.4.1


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