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authorDavid S. Miller <davem@davemloft.net>2005-07-05 15:20:09 -0700
committerDavid S. Miller <davem@davemloft.net>2005-07-05 15:20:09 -0700
commitaa93466bdfd901b926e033801f0b82b3eaa67be2 (patch)
tree5ee3bec452e795d48f380aee4494e06e5aba038e
parent7f4dd0a9438c73cbb1c240ece31390cf2c57294e (diff)
[TCP]: Eliminate redundant computations in tcp_write_xmit().
tcp_snd_test() is run for every packet output by a single call to tcp_write_xmit(), but this is not necessary. For one, the congestion window space needs to only be calculated one time, then used throughout the duration of the loop. This cleanup also makes experimenting with different TSO packetization schemes much easier. Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv4/tcp_output.c40
1 files changed, 31 insertions, 9 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 8327e5e86d1..0a4cd24b657 100644
--- 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;
}