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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: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/a7e1690c00c5dfe700c30eb9a8a81ec59f6545dd.1650884401.git.asml.silence@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Pavel Begunkov 2022-04-28 11:57:46 +01:00 committed by Jakub Kicinski
parent 0b9f1b265e
commit 829b7bdd70
1 changed files with 1 additions and 2 deletions
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3
net/core/skbuff.c
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@ -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;