Commit 33be96e4 authored by Haiyang Zhang's avatar Haiyang Zhang Committed by David S. Miller
Browse files

net/hyperv: Add flow control based on hi/low watermark 



In the existing code, we only stop queue when the ringbuffer is full,
so the current packet has to be dropped or retried from upper layer.

This patch stops the tx queue when available ringbuffer is below
the low watermark. So the ringbuffer still has small amount of space
available for the current packet. This will reduce the overhead of
retries on sending.

Signed-off-by: default avatarHaiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: default avatarK. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ede7193d

drivers/hv/ring_buffer.c

+0 −31
Original line number Original line Diff line number Diff line
@@ -30,37 +30,6 @@ 
#include "hyperv_vmbus.h"

#include "hyperv_vmbus.h"









/* #defines */





/* Amount of space to write to */

#define BYTES_AVAIL_TO_WRITE(r, w, z) \

	((w) >= (r)) ? ((z) - ((w) - (r))) : ((r) - (w))





/*

 *

 * hv_get_ringbuffer_availbytes()

 *

 * Get number of bytes available to read and to write to

 * for the specified ring buffer

 */

static inline void

hv_get_ringbuffer_availbytes(struct hv_ring_buffer_info *rbi,

			  u32 *read, u32 *write)

{

	u32 read_loc, write_loc;



	smp_read_barrier_depends();



	/* Capture the read/write indices before they changed */

	read_loc = rbi->ring_buffer->read_index;

	write_loc = rbi->ring_buffer->write_index;



	*write = BYTES_AVAIL_TO_WRITE(read_loc, write_loc, rbi->ring_datasize);

	*read = rbi->ring_datasize - *write;

}



/*

/*

 * hv_get_next_write_location()

 * hv_get_next_write_location()

 *

 *

drivers/net/hyperv/netvsc.c

+37 −4
Original line number Original line Diff line number Diff line
@@ -428,6 +428,24 @@ int netvsc_device_remove(struct hv_device *device) 
	return 0;

	return 0;

}

}







#define RING_AVAIL_PERCENT_HIWATER 20

#define RING_AVAIL_PERCENT_LOWATER 10



/*

 * Get the percentage of available bytes to write in the ring.

 * The return value is in range from 0 to 100.

 */

static inline u32 hv_ringbuf_avail_percent(

		struct hv_ring_buffer_info *ring_info)

{

	u32 avail_read, avail_write;



	hv_get_ringbuffer_availbytes(ring_info, &avail_read, &avail_write);



	return avail_write * 100 / ring_info->ring_datasize;

}



static void netvsc_send_completion(struct hv_device *device,

static void netvsc_send_completion(struct hv_device *device,

				   struct vmpacket_descriptor *packet)

				   struct vmpacket_descriptor *packet)

{

{
@@ -455,6 +473,8 @@ static void netvsc_send_completion(struct hv_device *device, 
		complete(&net_device->channel_init_wait);

		complete(&net_device->channel_init_wait);

	} else if (nvsp_packet->hdr.msg_type ==

	} else if (nvsp_packet->hdr.msg_type ==

		   NVSP_MSG1_TYPE_SEND_RNDIS_PKT_COMPLETE) {

		   NVSP_MSG1_TYPE_SEND_RNDIS_PKT_COMPLETE) {

		int num_outstanding_sends;



		/* Get the send context */

		/* Get the send context */

		nvsc_packet = (struct hv_netvsc_packet *)(unsigned long)

		nvsc_packet = (struct hv_netvsc_packet *)(unsigned long)

			packet->trans_id;

			packet->trans_id;
@@ -463,9 +483,13 @@ static void netvsc_send_completion(struct hv_device *device, 
		nvsc_packet->completion.send.send_completion(

		nvsc_packet->completion.send.send_completion(

			nvsc_packet->completion.send.send_completion_ctx);

			nvsc_packet->completion.send.send_completion_ctx);





		atomic_dec(&net_device->num_outstanding_sends);

		num_outstanding_sends =

			atomic_dec_return(&net_device->num_outstanding_sends);





		if (netif_queue_stopped(ndev) && !net_device->start_remove)

		if (netif_queue_stopped(ndev) && !net_device->start_remove &&

			(hv_ringbuf_avail_percent(&device->channel->outbound)

			> RING_AVAIL_PERCENT_HIWATER ||

			num_outstanding_sends < 1))

				netif_wake_queue(ndev);

				netif_wake_queue(ndev);

	} else {

	} else {

		netdev_err(ndev, "Unknown send completion packet type- "

		netdev_err(ndev, "Unknown send completion packet type- "
@@ -519,10 +543,19 @@ int netvsc_send(struct hv_device *device, 




	if (ret == 0) {

	if (ret == 0) {

		atomic_inc(&net_device->num_outstanding_sends);

		atomic_inc(&net_device->num_outstanding_sends);

		if (hv_ringbuf_avail_percent(&device->channel->outbound) <

			RING_AVAIL_PERCENT_LOWATER) {

			netif_stop_queue(ndev);

			if (atomic_read(&net_device->

				num_outstanding_sends) < 1)

				netif_wake_queue(ndev);

		}

	} else if (ret == -EAGAIN) {

	} else if (ret == -EAGAIN) {

		netif_stop_queue(ndev);

		netif_stop_queue(ndev);

		if (atomic_read(&net_device->num_outstanding_sends) < 1)

		if (atomic_read(&net_device->num_outstanding_sends) < 1) {

			netif_wake_queue(ndev);

			netif_wake_queue(ndev);

			ret = -ENOSPC;

		}

	} else {

	} else {

		netdev_err(ndev, "Unable to send packet %p ret %d\n",

		netdev_err(ndev, "Unable to send packet %p ret %d\n",

			   packet, ret);

			   packet, ret);

drivers/net/hyperv/netvsc_drv.c

+5 −1
Original line number Original line Diff line number Diff line
@@ -224,9 +224,13 @@ static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net) 
		net->stats.tx_packets++;

		net->stats.tx_packets++;

	} else {

	} else {

		kfree(packet);

		kfree(packet);

		if (ret != -EAGAIN) {

			dev_kfree_skb_any(skb);

			net->stats.tx_dropped++;

		}

	}

	}





	return ret ? NETDEV_TX_BUSY : NETDEV_TX_OK;

	return (ret == -EAGAIN) ? NETDEV_TX_BUSY : NETDEV_TX_OK;

}

}





/*

/*

include/linux/hyperv.h

+27 −0
Original line number Original line Diff line number Diff line
@@ -274,6 +274,33 @@ struct hv_ring_buffer_debug_info { 
	u32 bytes_avail_towrite;

	u32 bytes_avail_towrite;

};

};







/*

 *

 * hv_get_ringbuffer_availbytes()

 *

 * Get number of bytes available to read and to write to

 * for the specified ring buffer

 */

static inline void

hv_get_ringbuffer_availbytes(struct hv_ring_buffer_info *rbi,

			  u32 *read, u32 *write)

{

	u32 read_loc, write_loc, dsize;



	smp_read_barrier_depends();



	/* Capture the read/write indices before they changed */

	read_loc = rbi->ring_buffer->read_index;

	write_loc = rbi->ring_buffer->write_index;

	dsize = rbi->ring_datasize;



	*write = write_loc >= read_loc ? dsize - (write_loc - read_loc) :

		read_loc - write_loc;

	*read = dsize - *write;

}





/*

/*

 * We use the same version numbering for all Hyper-V modules.

 * We use the same version numbering for all Hyper-V modules.

 *

 *

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