On Wed, 2015-04-29 at 17:56 +0300, Madalin Bucur wrote:

This introduces the Freescale Data Path Acceleration Architecture
(DPAA) Ethernet driver (dpaa_eth) that builds upon the DPAA QMan,
BMan, PAMU and FMan drivers to deliver Ethernet connectivity on
the Freescale DPAA QorIQ platforms.

...

+	/* We're going to store the skb backpointer at the beginning
+	 * of the data buffer, so we need a privately owned skb
+	 */
+
+	/* Code borrowed from skb_unshare(). */
+	if (skb_cloned(skb)) {
+		struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
+
+		/* Finally, create a contig FD from this skb */
+		skb_to_contig_fd(priv, skb, &fd, countptr, &offset);
+
+		kfree_skb(skb);
+		skb = nskb;
+		/* skb_copy() has now linearized the skbuff. */
+	}
+

You know that TCP packets are clones, right ?
This code is killing performance.

TCP allows the headers part being modified by a driver if needed.

You should use skb_header_cloned() instead.