Commit 773ba4fe authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jakub Kicinski
Browse files

ipv6: avoid partial copy for zc 



Even when zerocopy transmission is requested and possible,
__ip_append_data() will still copy a small chunk of data just because it
allocated some extra linear space (e.g. 128 bytes). It wastes CPU cycles
on copy and iter manipulations and also misalignes potentially aligned
data. Avoid such copies. And as a bonus we can allocate smaller skb.

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 8eb77cc7

net/ipv6/ip6_output.c

+6 −1
Original line number Diff line number Diff line
@@ -1464,6 +1464,7 @@ static int __ip6_append_data(struct sock *sk, 
	int copy;

	int err;

	int offset = 0;

	bool zc = false;

	u32 tskey = 0;

	struct rt6_info *rt = (struct rt6_info *)cork->dst;

	struct ipv6_txoptions *opt = v6_cork->opt;
@@ -1549,6 +1550,7 @@ static int __ip6_append_data(struct sock *sk, 
		if (rt->dst.dev->features & NETIF_F_SG &&

		    csummode == CHECKSUM_PARTIAL) {

			paged = true;

			zc = true;

		} else {

			uarg->zerocopy = 0;

			skb_zcopy_set(skb, uarg, &extra_uref);
@@ -1630,9 +1632,12 @@ static int __ip6_append_data(struct sock *sk, 
				 (fraglen + alloc_extra < SKB_MAX_ALLOC ||

				  !(rt->dst.dev->features & NETIF_F_SG)))

				alloclen = fraglen;

			else {

			else if (!zc) {

				alloclen = min_t(int, fraglen, MAX_HEADER);

				pagedlen = fraglen - alloclen;

			} else {

				alloclen = fragheaderlen + transhdrlen;

				pagedlen = datalen - transhdrlen;

			}

			alloclen += alloc_extra;