netdev - [PATCH net-next 4/4] tcp: gro: micro optimizations in tcp[4]_gro

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Message-ID: <20240301193740.3436871-5-edumazet@google.com>
Date: Fri,  1 Mar 2024 19:37:40 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Richard Gobert <richardbgobert@...il.com>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 4/4] tcp: gro: micro optimizations in tcp[4]_gro_complete()

In tcp_gro_complete() :

Moving the skb->inner_transport_header setting
allows the compiler to reuse the previously loaded value
of skb->transport_header.

Caching skb_shinfo() avoids duplications as well.

In tcp4_gro_complete(), doing a single change on
skb_shinfo(skb)->gso_type also generates better code.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/tcp_offload.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index 875456efc92ddd546e13232dd775aaaf1093ce4f..b955ab3b236d965a38054efa004fe12f03074c70 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -299,18 +299,20 @@ struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb)
 void tcp_gro_complete(struct sk_buff *skb)
 {
 	struct tcphdr *th = tcp_hdr(skb);
+	struct skb_shared_info *shinfo;
+
+	if (skb->encapsulation)
+		skb->inner_transport_header = skb->transport_header;
 
 	skb->csum_start = (unsigned char *)th - skb->head;
 	skb->csum_offset = offsetof(struct tcphdr, check);
 	skb->ip_summed = CHECKSUM_PARTIAL;
 
-	skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
+	shinfo = skb_shinfo(skb);
+	shinfo->gso_segs = NAPI_GRO_CB(skb)->count;
 
 	if (th->cwr)
-		skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
-
-	if (skb->encapsulation)
-		skb->inner_transport_header = skb->transport_header;
+		shinfo->gso_type |= SKB_GSO_TCP_ECN;
 }
 EXPORT_SYMBOL(tcp_gro_complete);
 
@@ -335,10 +337,9 @@ INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
 
 	th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
 				  iph->daddr, 0);
-	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;
 
-	if (NAPI_GRO_CB(skb)->is_atomic)
-		skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_FIXEDID;
+	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4 |
+			(NAPI_GRO_CB(skb)->is_atomic * SKB_GSO_TCP_FIXEDID);
 
 	tcp_gro_complete(skb);
 	return 0;
-- 
2.44.0.278.ge034bb2e1d-goog