hv_netvsc: Eliminate memory allocation in the packet send path
The network protocol used to communicate with the host is the remote ndis (rndis)
protocol. We need to decorate each outgoing packet with a rndis header and
additional rndis state (rndis per-packet state). To manage this state, we
currently allocate memory in the transmit path. Eliminate this allocation by
requesting additional head room in the skb.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 75beb89..f9db6bc 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -235,7 +235,8 @@
struct sk_buff *skb = (struct sk_buff *)
(unsigned long)packet->send_completion_tid;
- kfree(packet);
+ if (!packet->part_of_skb)
+ kfree(packet);
if (skb)
dev_kfree_skb_any(skb);
@@ -383,6 +384,9 @@
u32 net_trans_info;
u32 hash;
u32 skb_length = skb->len;
+ u32 head_room = skb_headroom(skb);
+ u32 pkt_sz;
+ struct hv_page_buffer page_buf[MAX_PAGE_BUFFER_COUNT];
/* We will atmost need two pages to describe the rndis
@@ -397,24 +401,32 @@
return NETDEV_TX_OK;
}
- /* Allocate a netvsc packet based on # of frags. */
- packet = kzalloc(sizeof(struct hv_netvsc_packet) +
- (num_data_pgs * sizeof(struct hv_page_buffer)) +
- sizeof(struct rndis_message) +
- NDIS_VLAN_PPI_SIZE + NDIS_CSUM_PPI_SIZE +
- NDIS_LSO_PPI_SIZE + NDIS_HASH_PPI_SIZE, GFP_ATOMIC);
- if (!packet) {
- /* out of memory, drop packet */
- netdev_err(net, "unable to allocate hv_netvsc_packet\n");
+ pkt_sz = sizeof(struct hv_netvsc_packet) +
+ sizeof(struct rndis_message) +
+ NDIS_VLAN_PPI_SIZE + NDIS_CSUM_PPI_SIZE +
+ NDIS_LSO_PPI_SIZE + NDIS_HASH_PPI_SIZE;
- dev_kfree_skb(skb);
- net->stats.tx_dropped++;
- return NETDEV_TX_OK;
+ if (head_room < pkt_sz) {
+ packet = kmalloc(pkt_sz, GFP_ATOMIC);
+ if (!packet) {
+ /* out of memory, drop packet */
+ netdev_err(net, "unable to alloc hv_netvsc_packet\n");
+ dev_kfree_skb(skb);
+ net->stats.tx_dropped++;
+ return NETDEV_TX_OK;
+ }
+ packet->part_of_skb = false;
+ } else {
+ /* Use the headroom for building up the packet */
+ packet = (struct hv_netvsc_packet *)skb->head;
+ packet->part_of_skb = true;
}
+ packet->status = 0;
packet->xmit_more = skb->xmit_more;
packet->vlan_tci = skb->vlan_tci;
+ packet->page_buf = page_buf;
packet->q_idx = skb_get_queue_mapping(skb);
@@ -422,8 +434,13 @@
packet->total_data_buflen = skb->len;
packet->rndis_msg = (struct rndis_message *)((unsigned long)packet +
- sizeof(struct hv_netvsc_packet) +
- (num_data_pgs * sizeof(struct hv_page_buffer)));
+ sizeof(struct hv_netvsc_packet));
+
+ memset(packet->rndis_msg, 0, sizeof(struct rndis_message) +
+ NDIS_VLAN_PPI_SIZE +
+ NDIS_CSUM_PPI_SIZE +
+ NDIS_LSO_PPI_SIZE +
+ NDIS_HASH_PPI_SIZE);
/* Set the completion routine */
packet->send_completion = netvsc_xmit_completion;
@@ -555,7 +572,7 @@
rndis_msg->msg_len += rndis_msg_size;
packet->total_data_buflen = rndis_msg->msg_len;
packet->page_buf_cnt = init_page_array(rndis_msg, rndis_msg_size,
- skb, &packet->page_buf[0]);
+ skb, &page_buf[0]);
ret = netvsc_send(net_device_ctx->device_ctx, packet);
@@ -564,7 +581,8 @@
net->stats.tx_bytes += skb_length;
net->stats.tx_packets++;
} else {
- kfree(packet);
+ if (!packet->part_of_skb)
+ kfree(packet);
if (ret != -EAGAIN) {
dev_kfree_skb_any(skb);
net->stats.tx_dropped++;
@@ -846,12 +864,18 @@
struct netvsc_device_info device_info;
struct netvsc_device *nvdev;
int ret;
+ u32 max_needed_headroom;
net = alloc_etherdev_mq(sizeof(struct net_device_context),
num_online_cpus());
if (!net)
return -ENOMEM;
+ max_needed_headroom = sizeof(struct hv_netvsc_packet) +
+ sizeof(struct rndis_message) +
+ NDIS_VLAN_PPI_SIZE + NDIS_CSUM_PPI_SIZE +
+ NDIS_LSO_PPI_SIZE + NDIS_HASH_PPI_SIZE;
+
netif_carrier_off(net);
net_device_ctx = netdev_priv(net);
@@ -870,6 +894,13 @@
net->ethtool_ops = ðtool_ops;
SET_NETDEV_DEV(net, &dev->device);
+ /*
+ * Request additional head room in the skb.
+ * We will use this space to build the rndis
+ * heaser and other state we need to maintain.
+ */
+ net->needed_headroom = max_needed_headroom;
+
/* Notify the netvsc driver of the new device */
device_info.ring_size = ring_size;
ret = rndis_filter_device_add(dev, &device_info);