[PATCH net-next] net: mark deliver_skb() as unlikely and not inlined

[PATCH net-next] net: mark deliver_skb() as unlikely and not inlined

[Eric Dumazet]

deliver_skb() should not be inlined as is it not called
in the fast path.

Add unlikely() clauses giving hints to the compiler about this fact.

Before this patch:

size net/core/dev.o
   text	   data	    bss	    dec	    hex	filename
 121794	  13330	    176	 135300	  21084	net/core/dev.o

__netif_receive_skb_core() size on x86_64 : 4080 bytes.

After:

size net/core/dev.o
  text	   data	    bss	    dec	    hex	filenamee
 120330	  13338	    176	 133844	  20ad4	net/core/dev.o

__netif_receive_skb_core() size on x86_64 : 2781 bytes.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/core/dev.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index dccc1176f3c6565f96a7e2b5f42d009ef6435496..6886632b57605778284bb3dabdd05dfae5df37e0 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2463,9 +2463,9 @@ int dev_forward_skb_nomtu(struct net_device *dev, struct sk_buff *skb)
 	return __dev_forward_skb2(dev, skb, false) ?: netif_rx_internal(skb);
 }
 
-static inline int deliver_skb(struct sk_buff *skb,
-			      struct packet_type *pt_prev,
-			      struct net_device *orig_dev)
+static int deliver_skb(struct sk_buff *skb,
+		       struct packet_type *pt_prev,
+		       struct net_device *orig_dev)
 {
 	if (unlikely(skb_orphan_frags_rx(skb, GFP_ATOMIC)))
 		return -ENOMEM;
@@ -2484,7 +2484,7 @@ static inline void deliver_ptype_list_skb(struct sk_buff *skb,
 	list_for_each_entry_rcu(ptype, ptype_list, list) {
 		if (ptype->type != type)
 			continue;
-		if (pt_prev)
+		if (unlikely(pt_prev))
 			deliver_skb(skb, pt_prev, orig_dev);
 		pt_prev = ptype;
 	}
@@ -2545,7 +2545,7 @@ void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev)
 		if (skb_loop_sk(ptype, skb))
 			continue;
 
-		if (pt_prev) {
+		if (unlikely(pt_prev)) {
 			deliver_skb(skb2, pt_prev, skb->dev);
 			pt_prev = ptype;
 			continue;
@@ -4421,7 +4421,7 @@ sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
 		return skb;
 
 	bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
-	if (*pt_prev) {
+	if (unlikely(*pt_prev)) {
 		*ret = deliver_skb(skb, *pt_prev, orig_dev);
 		*pt_prev = NULL;
 	}
@@ -5883,7 +5883,7 @@ static inline int nf_ingress(struct sk_buff *skb, struct packet_type **pt_prev,
 	if (nf_hook_ingress_active(skb)) {
 		int ingress_retval;
 
-		if (*pt_prev) {
+		if (unlikely(*pt_prev)) {
 			*ret = deliver_skb(skb, *pt_prev, orig_dev);
 			*pt_prev = NULL;
 		}
@@ -5960,13 +5960,13 @@ static int __netif_receive_skb_core(struct sk_buff **pskb, bool pfmemalloc,
 
 	list_for_each_entry_rcu(ptype, &dev_net_rcu(skb->dev)->ptype_all,
 				list) {
-		if (pt_prev)
+		if (unlikely(pt_prev))
 			ret = deliver_skb(skb, pt_prev, orig_dev);
 		pt_prev = ptype;
 	}
 
 	list_for_each_entry_rcu(ptype, &skb->dev->ptype_all, list) {
-		if (pt_prev)
+		if (unlikely(pt_prev))
 			ret = deliver_skb(skb, pt_prev, orig_dev);
 		pt_prev = ptype;
 	}
@@ -5997,7 +5997,7 @@ static int __netif_receive_skb_core(struct sk_buff **pskb, bool pfmemalloc,
 	}
 
 	if (skb_vlan_tag_present(skb)) {
-		if (pt_prev) {
+		if (unlikely(pt_prev)) {
 			ret = deliver_skb(skb, pt_prev, orig_dev);
 			pt_prev = NULL;
 		}
@@ -6009,7 +6009,7 @@ static int __netif_receive_skb_core(struct sk_buff **pskb, bool pfmemalloc,
 
 	rx_handler = rcu_dereference(skb->dev->rx_handler);
 	if (rx_handler) {
-		if (pt_prev) {
+		if (unlikely(pt_prev)) {
 			ret = deliver_skb(skb, pt_prev, orig_dev);
 			pt_prev = NULL;
 		}
-- 
2.51.1.930.gacf6e81ea2-goog

Re: [PATCH net-next] net: mark deliver_skb() as unlikely and not inlined

[Jason Xing]

Hi Eric,

On Tue, Nov 4, 2025 at 12:53 AM Eric Dumazet <edumazet@google.com> wrote:
>
> deliver_skb() should not be inlined as is it not called
> in the fast path.

IIUC, it can be the fast path only when an af_packet socket attached to
ptype_all is used because it controls the filters in the rx/tx
directions? It even could be much hotter than __dev_queue_xmit() when
multiple af_packet sockets are created?

Thanks,
Jason

Re: [PATCH net-next] net: mark deliver_skb() as unlikely and not inlined

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon,  3 Nov 2025 16:52:56 +0000 you wrote:
> deliver_skb() should not be inlined as is it not called
> in the fast path.
> 
> Add unlikely() clauses giving hints to the compiler about this fact.
> 
> Before this patch:
> 
> [...]

Here is the summary with links:
  - [net-next] net: mark deliver_skb() as unlikely and not inlined
    https://git.kernel.org/netdev/net-next/c/46173144e03d

You are awesome, thank you!
-- 
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