Subject: [PATCH 3/3] tcp: Slightly optimize tcp_sendmsg

From: Krishna Kumar <[email-masked]>
Date: Wed, 09 Dec 2009 13:56:24 +0530

From: Krishna Kumar <[email-masked]>

Slightly optimize tcp_sendmsg since NETIF_F_SG is used many
times iteratively in the loop. The only other modification is
to change:
			} else if (i == MAX_SKB_FRAGS ||
				   (!i &&
				   !(sk->sk_route_caps & NETIF_F_SG))) {
	to:
			} else if (i == MAX_SKB_FRAGS || !sg) {

Signed-off-by: Krishna Kumar <[email-masked]>
---
 net/ipv4/tcp.c |   17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff -ruNp org/net/ipv4/tcp.c new/net/ipv4/tcp.c
--- org/net/ipv4/tcp.c	2009-12-09 10:01:35.000000000 +0530
+++ new/net/ipv4/tcp.c	2009-12-09 10:26:42.000000000 +0530
@@ -878,12 +878,12 @@ ssize_t tcp_sendpage(struct socket *sock
 #define TCP_PAGE(sk)	(sk->sk_sndmsg_page)
 #define TCP_OFF(sk)	(sk->sk_sndmsg_off)
 
-static inline int select_size(struct sock *sk)
+static inline int select_size(struct sock *sk, int sg)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	int tmp = tp->mss_cache;
 
-	if (sk->sk_route_caps & NETIF_F_SG) {
+	if (sg) {
 		if (sk_can_gso(sk))
 			tmp = 0;
 		else {
@@ -907,7 +907,7 @@ int tcp_sendmsg(struct kiocb *iocb, stru
 	struct sk_buff *skb;
 	int iovlen, flags;
 	int mss_now, size_goal;
-	int err, copied;
+	int sg, err, copied;
 	long timeo;
 
 	lock_sock(sk);
@@ -935,6 +935,8 @@ int tcp_sendmsg(struct kiocb *iocb, stru
 	if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
 		goto out_err;
 
+	sg = sk->sk_route_caps & NETIF_F_SG;
+
 	while (--iovlen >= 0) {
 		int seglen = iov->iov_len;
 		unsigned char __user *from = iov->iov_base;
@@ -960,8 +962,9 @@ new_segment:
 				if (!sk_stream_memory_free(sk))
 					goto wait_for_sndbuf;
 
-				skb = sk_stream_alloc_skb(sk, select_size(sk),
-						sk->sk_allocation);
+				skb = sk_stream_alloc_skb(sk,
+							  select_size(sk, sg),
+							  sk->sk_allocation);
 				if (!skb)
 					goto wait_for_memory;
 
@@ -998,9 +1001,7 @@ new_segment:
 					/* We can extend the last page
 					 * fragment. */
 					merge = 1;
-				} else if (i == MAX_SKB_FRAGS ||
-					   (!i &&
-					   !(sk->sk_route_caps & NETIF_F_SG))) {
+				} else if (i == MAX_SKB_FRAGS || !sg) {
 					/* Need to add new fragment and cannot
 					 * do this because interface is non-SG,
 					 * or because all the page slots are