[TCP]: Eliminate redundant computations in tcp_write_xmit().

[safe/jmp/linux-2.6] / net / ipv4 / tcp_output.c

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 8327e5e..0a4cd24 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -887,6 +887,7 @@ static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
 {
        struct tcp_sock *tp = tcp_sk(sk);
        struct sk_buff *skb;
+       unsigned int tso_segs, cwnd_quota;
        int sent_pkts;
 
        /* If we are closed, the bytes will have to remain here.
@@ -896,19 +897,31 @@ static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
        if (unlikely(sk->sk_state == TCP_CLOSE))
                return 0;
 
+       skb = sk->sk_send_head;
+       if (unlikely(!skb))
+               return 0;
+
+       tso_segs = tcp_init_tso_segs(sk, skb);
+       cwnd_quota = tcp_cwnd_test(tp, skb);
        sent_pkts = 0;
-       while ((skb = sk->sk_send_head) &&
-              tcp_snd_test(sk, skb, mss_now,
-                           tcp_skb_is_last(sk, skb) ? nonagle :
-                           TCP_NAGLE_PUSH)) {
-               if (skb->len > mss_now) {
-                       if (tcp_fragment(sk, skb, mss_now))
+
+       while (cwnd_quota >= tso_segs) {
+               if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
+                                            (tcp_skb_is_last(sk, skb) ?
+                                             nonagle : TCP_NAGLE_PUSH))))
+                       break;
+
+               if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
+                       break;
+
+               if (unlikely(skb->len > mss_now)) {
+                       if (unlikely(tcp_fragment(sk, skb,  mss_now)))
                                break;
                }
 
                TCP_SKB_CB(skb)->when = tcp_time_stamp;
                tcp_tso_set_push(skb);
-               if (tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC)))
+               if (unlikely(tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC))))
                        break;
 
                /* Advance the send_head.  This one is sent out.
@@ -917,10 +930,19 @@ static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
                update_send_head(sk, tp, skb);
 
                tcp_minshall_update(tp, mss_now, skb);
-               sent_pkts = 1;
+               sent_pkts++;
+
+               /* Do not optimize this to use tso_segs. If we chopped up
+                * the packet above, tso_segs will no longer be valid.
+                */
+               cwnd_quota -= tcp_skb_pcount(skb);
+               skb = sk->sk_send_head;
+               if (!skb)
+                       break;
+               tso_segs = tcp_init_tso_segs(sk, skb);
        }
 
-       if (sent_pkts) {
+       if (likely(sent_pkts)) {
                tcp_cwnd_validate(sk, tp);
                return 0;
        }