diff options
| author | Krishna Kumar <krkumar2@in.ibm.com> | 2009-12-10 07:16:59 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2009-12-23 14:13:29 -0800 |
| commit | def87cf42069a6d4fd42a2ede8f19c620a292568 (patch) | |
| tree | 1e8e97b452dd95d389feb4f04c0f25b6a9264412 /net/ipv4/tcp.c | |
| parent | afeca340c078e17ca233b3c68c3c3a70c56bfe1d (diff) | |
| download | lwn-def87cf42069a6d4fd42a2ede8f19c620a292568.tar.gz lwn-def87cf42069a6d4fd42a2ede8f19c620a292568.zip | |
tcp: Slightly optimize tcp_sendmsg
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 <krkumar2@in.ibm.com>
Acked-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp.c')
| -rw-r--r-- | net/ipv4/tcp.c | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 8a3f05adb39b..d5d69ea8f249 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 |