net: aquantia: optimize rx path using larger preallocated skb len

Atlantic driver used 14 bytes preallocated skb size. That made L3 protocol
processing inefficient because pskb_pull had to fetch all the L3/L4 headers
from extra fragments.

Specially on UDP flows that caused extra packet drops because CPU was
overloaded with pskb_pull.

This patch uses eth_get_headlen for skb preallocation.
Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/aquantia/atlantic/aq_cfg.h

@@ -38,6 +38,8 @@
 
 #define AQ_CFG_TX_CLEAN_BUDGET 256U
 
+#define AQ_CFG_RX_HDR_SIZE 256U
+
 /* LRO */
 #define AQ_CFG_IS_LRO_DEF           1U
 

drivers/net/ethernet/aquantia/atlantic/aq_ring.c

@@ -201,17 +201,18 @@ int aq_ring_rx_clean(struct aq_ring_s *self,
 		     int budget)
 {
 	struct net_device *ndev = aq_nic_get_ndev(self->aq_nic);
-	int err = 0;
 	bool is_rsc_completed = true;
+	int err = 0;
 
 	for (; (self->sw_head != self->hw_head) && budget;
 		self->sw_head = aq_ring_next_dx(self, self->sw_head),
 		--budget, ++(*work_done)) {
 		struct aq_ring_buff_s *buff = &self->buff_ring[self->sw_head];
+		struct aq_ring_buff_s *buff_ = NULL;
 		struct sk_buff *skb = NULL;
 		unsigned int next_ = 0U;
 		unsigned int i = 0U;
-		struct aq_ring_buff_s *buff_ = NULL;
+		u16 hdr_len;
 
 		if (buff->is_error) {
 			__free_pages(buff->page, 0);
@@ -255,20 +256,28 @@ int aq_ring_rx_clean(struct aq_ring_s *self,
 				err = -ENOMEM;
 				goto err_exit;
 			}
-
 			skb_put(skb, buff->len);
 		} else {
-			skb = netdev_alloc_skb(ndev, ETH_HLEN);
+			skb = napi_alloc_skb(napi, AQ_CFG_RX_HDR_SIZE);
 			if (unlikely(!skb)) {
 				err = -ENOMEM;
 				goto err_exit;
 			}
-			skb_put(skb, ETH_HLEN);
-			memcpy(skb->data, page_address(buff->page), ETH_HLEN);
 
-			skb_add_rx_frag(skb, 0, buff->page, ETH_HLEN,
-					buff->len - ETH_HLEN,
-					SKB_TRUESIZE(buff->len - ETH_HLEN));
+			hdr_len = buff->len;
+			if (hdr_len > AQ_CFG_RX_HDR_SIZE)
+				hdr_len = eth_get_headlen(page_address(buff->page),
+							  AQ_CFG_RX_HDR_SIZE);
+
+			memcpy(__skb_put(skb, hdr_len), page_address(buff->page),
+			       ALIGN(hdr_len, sizeof(long)));
+
+			if (buff->len - hdr_len > 0) {
+				skb_add_rx_frag(skb, 0, buff->page,
+						hdr_len,
+						buff->len - hdr_len,
+						SKB_TRUESIZE(buff->len - hdr_len));
+			}
 
 			if (!buff->is_eop) {
 				for (i = 1U, next_ = buff->next,