Merge branch 'tcp-gso-settings-defer'

Eric Dumazet says:

====================
tcp: defer shinfo->gso_size|type settings

We put shinfo->gso_segs in TCP_SKB_CB(skb) a while back for performance
reasons.

This was in commit cd7d8498c9a5 ("tcp: change tcp_skb_pcount() location")

This patch series complete the job for gso_size and gso_type, so that
we do not bring 2 extra cache lines in tcp write xmit fast path,
and making tcp_init_tso_segs() simpler and faster.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 34 insertions, 46 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 978cebe..950cfec 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -730,11 +730,14 @@ struct tcp_skb_cb {
 		/* Note : tcp_tw_isn is used in input path only
 		 *	  (isn chosen by tcp_timewait_state_process())
 		 *
-		 * 	  tcp_gso_segs is used in write queue only,
-		 *	  cf tcp_skb_pcount()
+		 * 	  tcp_gso_segs/size are used in write queue only,
+		 *	  cf tcp_skb_pcount()/tcp_skb_mss()
 		 */
 		__u32		tcp_tw_isn;
-		__u32		tcp_gso_segs;
+		struct {
+			u16	tcp_gso_segs;
+			u16	tcp_gso_size;
+		};
 	};
 	__u8		tcp_flags;	/* TCP header flags. (tcp[13])	*/
 
@@ -790,10 +793,10 @@ static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
 	TCP_SKB_CB(skb)->tcp_gso_segs += segs;
 }
 
-/* This is valid iff tcp_skb_pcount() > 1. */
+/* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
 static inline int tcp_skb_mss(const struct sk_buff *skb)
 {
-	return skb_shinfo(skb)->gso_size;
+	return TCP_SKB_CB(skb)->tcp_gso_size;
 }
 
 /* Events passed to congestion control interface */
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d4f76ab..684f095 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1316,16 +1316,12 @@ static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
 	 * code can come after this skb later on it's better to keep
 	 * setting gso_size to something.
 	 */
-	if (!skb_shinfo(prev)->gso_size) {
-		skb_shinfo(prev)->gso_size = mss;
-		skb_shinfo(prev)->gso_type = sk->sk_gso_type;
-	}
+	if (!TCP_SKB_CB(prev)->tcp_gso_size)
+		TCP_SKB_CB(prev)->tcp_gso_size = mss;
 
 	/* CHECKME: To clear or not to clear? Mimics normal skb currently */
-	if (tcp_skb_pcount(skb) <= 1) {
-		skb_shinfo(skb)->gso_size = 0;
-		skb_shinfo(skb)->gso_type = 0;
-	}
+	if (tcp_skb_pcount(skb) <= 1)
+		TCP_SKB_CB(skb)->tcp_gso_size = 0;
 
 	/* Difference in this won't matter, both ACKed by the same cumul. ACK */
 	TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);
@@ -2252,7 +2248,7 @@ static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
 			    (oldcnt >= packets))
 				break;
 
-			mss = skb_shinfo(skb)->gso_size;
+			mss = tcp_skb_mss(skb);
 			err = tcp_fragment(sk, skb, (packets - oldcnt) * mss,
 					   mss, GFP_ATOMIC);
 			if (err < 0)
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index 3f7c2fc..9864a2d 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -77,7 +77,7 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
 	oldlen = (u16)~skb->len;
 	__skb_pull(skb, thlen);
 
-	mss = tcp_skb_mss(skb);
+	mss = skb_shinfo(skb)->gso_size;
 	if (unlikely(skb->len <= mss))
 		goto out;
 
@@ -242,7 +242,7 @@ found:
 		flush |= *(u32 *)((u8 *)th + i) ^
 			 *(u32 *)((u8 *)th2 + i);
 
-	mss = tcp_skb_mss(p);
+	mss = skb_shinfo(p)->gso_size;
 
 	flush |= (len - 1) >= mss;
 	flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index eeb59be..b1c218d 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -402,8 +402,6 @@ static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
  */
 static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
 {
-	struct skb_shared_info *shinfo = skb_shinfo(skb);
-
 	skb->ip_summed = CHECKSUM_PARTIAL;
 	skb->csum = 0;
 
@@ -411,8 +409,6 @@ static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
 	TCP_SKB_CB(skb)->sacked = 0;
 
 	tcp_skb_pcount_set(skb, 1);
-	shinfo->gso_size = 0;
-	shinfo->gso_type = 0;
 
 	TCP_SKB_CB(skb)->seq = seq;
 	if (flags & (TCPHDR_SYN | TCPHDR_FIN))
@@ -1003,6 +999,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 	}
 
 	tcp_options_write((__be32 *)(th + 1), tp, &opts);
+	skb_shinfo(skb)->gso_type = sk->sk_gso_type;
 	if (likely((tcb->tcp_flags & TCPHDR_SYN) == 0))
 		tcp_ecn_send(sk, skb, tcp_header_size);
 
@@ -1028,8 +1025,9 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 			      tcp_skb_pcount(skb));
 
 	tp->segs_out += tcp_skb_pcount(skb);
-	/* OK, its time to fill skb_shinfo(skb)->gso_segs */
+	/* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
 	skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
+	skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
 
 	/* Our usage of tstamp should remain private */
 	skb->tstamp.tv64 = 0;
@@ -1066,25 +1064,17 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
 }
 
 /* Initialize TSO segments for a packet. */
-static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
-				 unsigned int mss_now)
+static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
 {
-	struct skb_shared_info *shinfo = skb_shinfo(skb);
-
-	/* Make sure we own this skb before messing gso_size/gso_segs */
-	WARN_ON_ONCE(skb_cloned(skb));
-
 	if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
 		/* Avoid the costly divide in the normal
 		 * non-TSO case.
 		 */
 		tcp_skb_pcount_set(skb, 1);
-		shinfo->gso_size = 0;
-		shinfo->gso_type = 0;
+		TCP_SKB_CB(skb)->tcp_gso_size = 0;
 	} else {
 		tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
-		shinfo->gso_size = mss_now;
-		shinfo->gso_type = sk->sk_gso_type;
+		TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
 	}
 }
 
@@ -1216,8 +1206,8 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
 	old_factor = tcp_skb_pcount(skb);
 
 	/* Fix up tso_factor for both original and new SKB.  */
-	tcp_set_skb_tso_segs(sk, skb, mss_now);
-	tcp_set_skb_tso_segs(sk, buff, mss_now);
+	tcp_set_skb_tso_segs(skb, mss_now);
+	tcp_set_skb_tso_segs(buff, mss_now);
 
 	/* If this packet has been sent out already, we must
 	 * adjust the various packet counters.
@@ -1297,7 +1287,7 @@ int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
 
 	/* Any change of skb->len requires recalculation of tso factor. */
 	if (tcp_skb_pcount(skb) > 1)
-		tcp_set_skb_tso_segs(sk, skb, tcp_skb_mss(skb));
+		tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
 
 	return 0;
 }
@@ -1629,13 +1619,12 @@ static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
  * This must be invoked the first time we consider transmitting
  * SKB onto the wire.
  */
-static int tcp_init_tso_segs(const struct sock *sk, struct sk_buff *skb,
-			     unsigned int mss_now)
+static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
 {
 	int tso_segs = tcp_skb_pcount(skb);
 
 	if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
-		tcp_set_skb_tso_segs(sk, skb, mss_now);
+		tcp_set_skb_tso_segs(skb, mss_now);
 		tso_segs = tcp_skb_pcount(skb);
 	}
 	return tso_segs;
@@ -1690,7 +1679,7 @@ static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
 	const struct tcp_sock *tp = tcp_sk(sk);
 	unsigned int cwnd_quota;
 
-	tcp_init_tso_segs(sk, skb, cur_mss);
+	tcp_init_tso_segs(skb, cur_mss);
 
 	if (!tcp_nagle_test(tp, skb, cur_mss, nonagle))
 		return 0;
@@ -1759,8 +1748,8 @@ static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
 	tcp_fragment_tstamp(skb, buff);
 
 	/* Fix up tso_factor for both original and new SKB.  */
-	tcp_set_skb_tso_segs(sk, skb, mss_now);
-	tcp_set_skb_tso_segs(sk, buff, mss_now);
+	tcp_set_skb_tso_segs(skb, mss_now);
+	tcp_set_skb_tso_segs(buff, mss_now);
 
 	/* Link BUFF into the send queue. */
 	__skb_header_release(buff);
@@ -1994,7 +1983,7 @@ static int tcp_mtu_probe(struct sock *sk)
 								 skb->len, 0);
 			} else {
 				__pskb_trim_head(skb, copy);
-				tcp_set_skb_tso_segs(sk, skb, mss_now);
+				tcp_set_skb_tso_segs(skb, mss_now);
 			}
 			TCP_SKB_CB(skb)->seq += copy;
 		}
@@ -2004,7 +1993,7 @@ static int tcp_mtu_probe(struct sock *sk)
 		if (len >= probe_size)
 			break;
 	}
-	tcp_init_tso_segs(sk, nskb, nskb->len);
+	tcp_init_tso_segs(nskb, nskb->len);
 
 	/* We're ready to send.  If this fails, the probe will
 	 * be resegmented into mss-sized pieces by tcp_write_xmit().
@@ -2066,7 +2055,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 	while ((skb = tcp_send_head(sk))) {
 		unsigned int limit;
 
-		tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
+		tso_segs = tcp_init_tso_segs(skb, mss_now);
 		BUG_ON(!tso_segs);
 
 		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
@@ -2620,7 +2609,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 		if (unlikely(oldpcount > 1)) {
 			if (skb_unclone(skb, GFP_ATOMIC))
 				return -ENOMEM;
-			tcp_init_tso_segs(sk, skb, cur_mss);
+			tcp_init_tso_segs(skb, cur_mss);
 			tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb));
 		}
 	}
@@ -3457,7 +3446,7 @@ int tcp_write_wakeup(struct sock *sk, int mib)
 			if (tcp_fragment(sk, skb, seg_size, mss, GFP_ATOMIC))
 				return -1;
 		} else if (!tcp_skb_pcount(skb))
-			tcp_set_skb_tso_segs(sk, skb, mss);
+			tcp_set_skb_tso_segs(skb, mss);
 
 		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
 		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);