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: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 8af25a0..7233c88 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -30,37 +30,6 @@
#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()
*
diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index d025c83..8b91947 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -428,6 +428,24 @@
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,
struct vmpacket_descriptor *packet)
{
@@ -455,6 +473,8 @@
complete(&net_device->channel_init_wait);
} else if (nvsp_packet->hdr.msg_type ==
NVSP_MSG1_TYPE_SEND_RNDIS_PKT_COMPLETE) {
+ int num_outstanding_sends;
+
/* Get the send context */
nvsc_packet = (struct hv_netvsc_packet *)(unsigned long)
packet->trans_id;
@@ -463,10 +483,14 @@
nvsc_packet->completion.send.send_completion(
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)
- netif_wake_queue(ndev);
+ 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);
} else {
netdev_err(ndev, "Unknown send completion packet type- "
"%d received!!\n", nvsp_packet->hdr.msg_type);
@@ -519,10 +543,19 @@
if (ret == 0) {
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) {
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);
+ ret = -ENOSPC;
+ }
} else {
netdev_err(ndev, "Unable to send packet %p ret %d\n",
packet, ret);
diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index dd29478..a0cc127 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -224,9 +224,13 @@
net->stats.tx_packets++;
} else {
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;
}
/*