Commit 829b7bdd authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jakub Kicinski
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tcp: optimise skb_zerocopy_iter_stream() 



It's expensive to make a copy of 40B struct iov_iter to the point it
was taking 0.2-0.5% of all cycles in my tests. iov_iter_revert() should
be fine as it's a simple case without nested reverts/truncates.

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/a7e1690c00c5dfe700c30eb9a8a81ec59f6545dd.1650884401.git.asml.silence@gmail.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 0b9f1b26

net/core/skbuff.c

+1 −2
Original line number Diff line number Diff line
@@ -1344,7 +1344,6 @@ int skb_zerocopy_iter_stream(struct sock *sk, struct sk_buff *skb, 
			     struct ubuf_info *uarg)

{

	struct ubuf_info *orig_uarg = skb_zcopy(skb);

	struct iov_iter orig_iter = msg->msg_iter;

	int err, orig_len = skb->len;



	/* An skb can only point to one uarg. This edge case happens when
@@ -1358,7 +1357,7 @@ int skb_zerocopy_iter_stream(struct sock *sk, struct sk_buff *skb, 
		struct sock *save_sk = skb->sk;



		/* Streams do not free skb on error. Reset to prev state. */

		msg->msg_iter = orig_iter;

		iov_iter_revert(&msg->msg_iter, skb->len - orig_len);

		skb->sk = sk;

		___pskb_trim(skb, orig_len);

		skb->sk = save_sk;