netdev - [PATCH net-next] inet: Save one atomic op if no memcg to charge

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Message-Id: <20230619082547.73929-1-wuyun.abel@bytedance.com>
Date: Mon, 19 Jun 2023 16:25:47 +0800
From: Abel Wu <wuyun.abel@...edance.com>
To: "David S. Miller" <davem@...emloft.net>,
	David Ahern <dsahern@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Abel Wu <wuyun.abel@...edance.com>,
	netdev@...r.kernel.org (open list:NETWORKING [IPv4/IPv6]),
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH net-next] inet: Save one atomic op if no memcg to charge

If there is no net-memcg associated with the sock, don't bother
calculating its memory usage for charge.

Signed-off-by: Abel Wu <wuyun.abel@...edance.com>
---
 net/ipv4/inet_connection_sock.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 65ad4251f6fd..73798282c1ef 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -706,20 +706,24 @@ struct sock *inet_csk_accept(struct sock *sk, int flags, int *err, bool kern)
 out:
 	release_sock(sk);
 	if (newsk && mem_cgroup_sockets_enabled) {
-		int amt;
+		int amt = 0;
 
 		/* atomically get the memory usage, set and charge the
 		 * newsk->sk_memcg.
 		 */
 		lock_sock(newsk);
 
-		/* The socket has not been accepted yet, no need to look at
-		 * newsk->sk_wmem_queued.
-		 */
-		amt = sk_mem_pages(newsk->sk_forward_alloc +
-				   atomic_read(&newsk->sk_rmem_alloc));
 		mem_cgroup_sk_alloc(newsk);
-		if (newsk->sk_memcg && amt)
+		if (newsk->sk_memcg) {
+			/* The socket has not been accepted yet, no need
+			 * to look at newsk->sk_wmem_queued.
+			 */
+			amt = sk_mem_pages(newsk->sk_forward_alloc +
+					   atomic_read(&newsk->sk_rmem_alloc));
+
+		}
+
+		if (amt)
 			mem_cgroup_charge_skmem(newsk->sk_memcg, amt,
 						GFP_KERNEL | __GFP_NOFAIL);
 
-- 
2.37.3