netdev - [PATCH net-next 19/20] tcp: do not call tcp_cleanup

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Date:   Mon, 15 Nov 2021 11:02:48 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Arjun Roy <arjunroy@...gle.com>
Subject: [PATCH net-next 19/20] tcp: do not call tcp_cleanup_rbuf() if we have a backlog

From: Eric Dumazet <edumazet@...gle.com>

Under pressure, tcp recvmsg() has logic to process the socket backlog,
but calls tcp_cleanup_rbuf() right before.

Avoiding sending ACK right before processing new segments makes
a lot of sense, as this decrease the number of ACK packets,
with no impact on effective ACK clocking.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/tcp.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 7b1886103556e1295d84378d5bcb0f0346651de0..d1949fdb1462b97b87b99bc32ea132c574e9b647 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2436,12 +2436,11 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
 			}
 		}
 
-		tcp_cleanup_rbuf(sk, copied);
-
 		if (copied >= target) {
 			/* Do not sleep, just process backlog. */
 			__sk_flush_backlog(sk);
 		} else {
+			tcp_cleanup_rbuf(sk, copied);
 			sk_defer_free_flush(sk);
 			sk_wait_data(sk, &timeo, last);
 		}
-- 
2.34.0.rc1.387.gb447b232ab-goog