netdev - [PATCH net-next 11/20] tcp: small optimization in tcp recvmsg()

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Message-Id: <20211115190249.3936899-12-eric.dumazet@gmail.com>
Date:   Mon, 15 Nov 2021 11:02:40 -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 11/20] tcp: small optimization in tcp recvmsg()

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

When reading large chunks of data, incoming packets might
be added to the backlog from BH.

tcp recvmsg() detects the backlog queue is not empty, and uses
a release_sock()/lock_sock() pair to process this backlog.

We now have __sk_flush_backlog() to perform this
a bit faster.

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 862e8cb8dda51e76300a427783a7d8c32e82cc7f..24d77a32c9cbcdf0e4380ec6d9aa3e42d2cf8730 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2409,8 +2409,7 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
 
 		if (copied >= target) {
 			/* Do not sleep, just process backlog. */
-			release_sock(sk);
-			lock_sock(sk);
+			__sk_flush_backlog(sk);
 		} else {
 			sk_wait_data(sk, &timeo, last);
 		}
-- 
2.34.0.rc1.387.gb447b232ab-goog