Commit 79bfa5fb authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

net: fclone allocation small optimization 



After skb allocation, initial skb->fclone value is 0 (SKB_FCLONE_UNAVAILABLE)

We can replace one RMW sequence with a single OR instruction.

	movzbl 0x7e(%r13),%eax // skb->fclone = SKB_FCLONE_ORIG;
	and    $0xf3,%al
	or     $0x4,%al
	mov    %al,0x7e(%r13)
->
	or     $0x4,0x7e(%r13) // skb->fclone |= SKB_FCLONE_ORIG;

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260116164402.1872649-1-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent ee7be82f

net/core/skbuff.c

+8 −1
Original line number Diff line number Diff line
@@ -723,7 +723,14 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask, 


		fclones = container_of(skb, struct sk_buff_fclones, skb1);



		skb->fclone = SKB_FCLONE_ORIG;

		/* skb->fclone is a 2bits field.

		 * Replace expensive RMW (skb->fclone = SKB_FCLONE_ORIG)

		 * with a single OR.

		 */

		BUILD_BUG_ON(SKB_FCLONE_UNAVAILABLE != 0);

		DEBUG_NET_WARN_ON_ONCE(skb->fclone != SKB_FCLONE_UNAVAILABLE);

		skb->fclone |= SKB_FCLONE_ORIG;



		refcount_set(&fclones->fclone_ref, 1);

	}