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hv_netvsc: Use the xmit_more skb flag to optimize signaling the host

PATCH Superseded K. Y. Srinivasan 3 participants 4 messages May 11, 2015

Subsystems (3)
Networking Network drivers Hyper-V/Azure core and drivers

v5 of 6 Superseded Latest is v6 →

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K. Y. Srinivasan

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#0 lore raw

PATCH v5 1/1 hv_netvsc: Use the xmit_more skb flag to optimize signaling the host

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 <[email protected]>

---
v2: Fixed up indentation based on feedback from David Miller.
v3,v4: If the queue could be stopped, deal with that condition: Eric Dumazet <[email protected]>
v5: Fixed up indentation based on feedback from David Miller.

 drivers/net/hyperv/netvsc.c |   41 +++++++++++++++++++++++++++--------------
 1 files changed, 27 insertions(+), 14 deletions(-)
drivers/net/hyperv/netvsc.c +27 -14
index ea091bc..7fdf3e8 100644
@@ -743,6 +743,8 @@ 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;
+	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) {

@@ -769,30 +771,41 @@ 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_flags,
+						      !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_flags, !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) {
+		if (ring_avail < RING_AVAIL_PERCENT_LOWATER) {
 			netif_tx_stop_queue(netdev_get_tx_queue(
 					    ndev, q_idx));
Signature · 1 line
1.7.4.1
#1 lore raw
Quoted 4 lines · 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.

trivia:

I think that indirecting VMBUS_DATA_PACKET_FLAG_COMPLETTION_REQUESTED into a non-const temporary isn't very useful.

Whenever overly long identifiers like VMBUS_<FOO> is used, I think that it'd be better to use it directly and ignore 80 column warnings.

Same with the "sizeof(struct nvsp_message)" on two lines.

drivers/net/hyperv/netvsc.c

Quoted 1 line
drivers/net/hyperv/netvsc.c +0 -0

[]

drivers/net/hyperv/netvsc.c static inline int netvsc_send_pkt( · line 747

Quoted 6 lines
drivers/net/hyperv/netvsc.c +2 -0
@@ -743,6 +743,8 @@ 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;
+	u32 ring_avail = hv_ringbuf_avail_percent(&out_channel->outbound);

[]

drivers/net/hyperv/netvsc.c static inline int netvsc_send_pkt(

Quoted 1 line
drivers/net/hyperv/netvsc.c +0 -0
@@ -769,30 +771,41 @@ static inline int netvsc_send_pkt(

[]

drivers/net/hyperv/netvsc.c static inline int netvsc_send_pkt( · line 795

Quoted 9 lines
drivers/net/hyperv/netvsc.c +9 -0
+		ret = vmbus_sendpacket_pagebuffer_ctl(out_channel,
+						      pgbuf,
+						      packet->page_buf_cnt,
+						      &nvmsg,
+						      sizeof(struct
+							     nvsp_message),
+						      req_id,
+						      vmbus_flags,
+						      !packet->xmit_more);

[]

drivers/net/hyperv/netvsc.c static inline int netvsc_send_pkt( · line 810

Quoted 2 lines
drivers/net/hyperv/netvsc.c +0 -0
 			netif_tx_stop_queue(netdev_get_tx_queue(
 					    ndev, q_idx));

This could be on one line too.

author
#2 lore raw
Quoted 22 lines

-----Original Message-----
From: Joe Perches [mailto:[email protected]]
Sent: Sunday, May 10, 2015 10:58 PM
To: KY Srinivasan
Cc: [email protected]; [email protected]; linux- [email protected]; [email protected]; [email protected]; [email protected]; [email protected]
Subject: Re: [PATCH V5 1/1] hv_netvsc: Use the xmit_more skb flag to optimize signaling the host

Quoted 2 lines · 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

Quoted 1 line

make the host more efficient since it can potentially process a larger batch

of

Quoted 1 line

packets. Implement this optimization.

trivia:

Quoted 7 lines

I think that indirecting
VMBUS_DATA_PACKET_FLAG_COMPLETTION_REQUESTED
into a non-const temporary isn't very useful.

Whenever overly long identifiers like VMBUS_<FOO> is used, I think that it'd be better to use it directly and ignore 80 column warnings.

Thanks Joe; if Dave agrees, I can send v6 of this patch out.

Regards,

K. Y

Quoted 33 lines

Same with the "sizeof(struct nvsp_message)" on two lines.

drivers/net/hyperv/netvsc.c

Quoted 1 line
drivers/net/hyperv/netvsc.c +0 -0

[]

drivers/net/hyperv/netvsc.c static inline int netvsc_send_pkt( · line 746

Quoted 5 lines
drivers/net/hyperv/netvsc.c +1 -0
@@ -743,6 +743,8 @@ 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;

drivers/net/hyperv/netvsc.c static inline int netvsc_send_pkt( · line 748

Quoted 2 lines
drivers/net/hyperv/netvsc.c +1 -0
+	u32 ring_avail = hv_ringbuf_avail_percent(&out_channel-
 outbound);

[]

drivers/net/hyperv/netvsc.c static inline int netvsc_send_pkt(

Quoted 1 line
drivers/net/hyperv/netvsc.c +0 -0
@@ -769,30 +771,41 @@ static inline int netvsc_send_pkt(

[]

drivers/net/hyperv/netvsc.c static inline int netvsc_send_pkt( · line 795

Quoted 9 lines
drivers/net/hyperv/netvsc.c +9 -0
+		ret = vmbus_sendpacket_pagebuffer_ctl(out_channel,
+						      pgbuf,
+						      packet->page_buf_cnt,
+						      &nvmsg,
+						      sizeof(struct
+							     nvsp_message),
+						      req_id,
+						      vmbus_flags,
+						      !packet->xmit_more);

[]

drivers/net/hyperv/netvsc.c static inline int netvsc_send_pkt( · line 810

Quoted 2 lines
drivers/net/hyperv/netvsc.c +0 -0
 			netif_tx_stop_queue(netdev_get_tx_queue(
 					    ndev, q_idx));

This could be on one line too.

maintainer
#3 lore raw

From: KY Srinivasan <[email protected]>
Date: Mon, 11 May 2015 08:59:53 +0000

Quoted 26 lines
Quoted 26 lines

-----Original Message-----
From: Joe Perches [mailto:[email protected]]
Sent: Sunday, May 10, 2015 10:58 PM
To: KY Srinivasan
Cc: [email protected]; [email protected]; linux- [email protected]; [email protected]; [email protected]; [email protected]; [email protected]
Subject: Re: [PATCH V5 1/1] hv_netvsc: Use the xmit_more skb flag to optimize signaling the host

Quoted 2 lines · 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

Quoted 1 line

make the host more efficient since it can potentially process a larger batch

of

Quoted 1 line

packets. Implement this optimization.

trivia:

I think that indirecting
VMBUS_DATA_PACKET_FLAG_COMPLETTION_REQUESTED
into a non-const temporary isn't very useful.

Quoted 5 lines
Quoted 3 lines

Whenever overly long identifiers like VMBUS_<FOO> is used, I think that it'd be better to use it directly and ignore 80 column warnings.

Thanks Joe; if Dave agrees, I can send v6 of this patch out.

Sure, respin a v6.