e1000: switch to napi_build_skb()

napi_build_skb() reuses per-cpu NAPI skbuff_head cache in order
to save some cycles on freeing/allocating skbuff_heads on every
new Rx or completed Tx element.
e1000 driver runs Tx completion polling cycle right before the Rx
one. Now that e1000 uses napi_consume_skb() to put skbuff_heads of
completed entries into the cache, it will never empty and always
warm at that moment. Switch to the napi_build_skb() to relax mm
pressure on heavy Rx and increase throughput.
Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Tested-by: Tony Brelinski <tony.brelinski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/e1000/e1000_main.c

@@ -4384,7 +4384,7 @@ static bool e1000_clean_rx_irq(struct e1000_adapter *adapter,
 		if (!skb) {
 			unsigned int frag_len = e1000_frag_len(adapter);
 
-			skb = build_skb(data - E1000_HEADROOM, frag_len);
+			skb = napi_build_skb(data - E1000_HEADROOM, frag_len);
 			if (!skb) {
 				adapter->alloc_rx_buff_failed++;
 				break;