From def87cf42069a6d4fd42a2ede8f19c620a292568 Mon Sep 17 00:00:00 2001 From: Krishna Kumar Date: Thu, 10 Dec 2009 07:16:59 +0000 Subject: [PATCH] tcp: Slightly optimize tcp_sendmsg MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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) { The reason why this change is correct: this code (other than the MAX_SKB_FRAGS case) executes only due to the else part of: "if (skb_tailroom(skb) > 0) {" - i.e. there was no space in the skb to put the data inline. Hence SG is false is a sufficient condition, and there is no way a fragment can be added to the skb. Changelog: - Added the above explanation for the change Signed-off-by: Krishna Kumar Acked-by: Ilpo Järvinen Signed-off-by: David S. Miller --- net/ipv4/tcp.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 8a3f05a..d5d69ea 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -876,12 +876,12 @@ ssize_t tcp_sendpage(struct socket *sock, struct page *page, int offset, #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 { @@ -905,7 +905,7 @@ int tcp_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg, struct sk_buff *skb; int iovlen, flags; int mss_now, size_goal; - int err, copied; + int sg, err, copied; long timeo; lock_sock(sk); @@ -933,6 +933,8 @@ int tcp_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg, 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; @@ -958,8 +960,9 @@ 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; @@ -996,9 +999,7 @@ 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 -- 2.7.4