From 9e542ff8b79ae1871074d3a7dca7de9e7374eeda Mon Sep 17 00:00:00 2001 From: Breno Leitao Date: Tue, 8 Oct 2024 09:32:04 -0700 Subject: [PATCH] net: Remove likely from l3mdev_master_ifindex_by_index The likely() annotation in l3mdev_master_ifindex_by_index() has been found to be incorrect 100% of the time in real-world workloads (e.g., web servers). Annotated branches shows the following in these servers: correct incorrect % Function File Line 0 169053813 100 l3mdev_master_ifindex_by_index l3mdev.h 81 This is happening because l3mdev_master_ifindex_by_index() is called from __inet_check_established(), which calls l3mdev_master_ifindex_by_index() passing the socked bounded interface. l3mdev_master_ifindex_by_index(net, sk->sk_bound_dev_if); Since most sockets are not going to be bound to a network device, the likely() is giving the wrong assumption. Remove the likely() annotation to ensure more accurate branch prediction. Signed-off-by: Breno Leitao Reviewed-by: David Ahern Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20241008163205.3939629-1-leitao@debian.org Signed-off-by: Paolo Abeni --- include/net/l3mdev.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/net/l3mdev.h b/include/net/l3mdev.h index 031c661aa14df..2d6141f28b530 100644 --- a/include/net/l3mdev.h +++ b/include/net/l3mdev.h @@ -78,7 +78,7 @@ static inline int l3mdev_master_ifindex_by_index(struct net *net, int ifindex) struct net_device *dev; int rc = 0; - if (likely(ifindex)) { + if (ifindex) { rcu_read_lock(); dev = dev_get_by_index_rcu(net, ifindex);