When `skb_splice_from_iter` was introduced, it inadvertently added checksumming for AF_UNIX sockets. This resulted in significant slowdowns, for example when using sendfile over unix sockets.
Using the test code in [1] in my test setup (2G single core qemu), the client receives a 1000M file in: - without the patch: 1482ms (+/- 36ms) - with the patch: 652.5ms (+/- 22.9ms)
This commit addresses the issue by marking checksumming as unnecessary in `unix_stream_sendmsg`
Cc: stable@vger.kernel.org Signed-off-by: Frederik Deweerdt deweerdt.lkml@gmail.com Fixes: 2e910b95329c ("net: Add a function to splice pages into an skbuff for MSG_SPLICE_PAGES") --- net/unix/af_unix.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 001ccc55ef0f..6b1762300443 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -2313,6 +2313,7 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg, fds_sent = true;
if (unlikely(msg->msg_flags & MSG_SPLICE_PAGES)) { + skb->ip_summed = CHECKSUM_UNNECESSARY; err = skb_splice_from_iter(skb, &msg->msg_iter, size, sk->sk_allocation); if (err < 0) {