tcp: don't clear retransmit_skb_hint when not necessary

Most importantly avoid doing it with cumulative ACK. Not clearing
means that we no longer need n^2 processing in resolution of each
fast recovery.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 220f54c..ea81572 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1037,10 +1037,15 @@ static inline void tcp_mib_init(struct net *net)
 }
 
 /* from STCP */
-static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
+static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
 {
        tp->lost_skb_hint = NULL;
        tp->scoreboard_skb_hint = NULL;
+}
+
+static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
+{
+       tcp_clear_retrans_hints_partial(tp);
        tp->retransmit_skb_hint = NULL;
 }
 

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d017aed..44a4fff 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2925,7 +2925,9 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
 
                tcp_unlink_write_queue(skb, sk);
                sk_wmem_free_skb(sk, skb);
-               tcp_clear_all_retrans_hints(tp);
+               tcp_clear_retrans_hints_partial(tp);
+               if (skb == tp->retransmit_skb_hint)
+                       tp->retransmit_skb_hint = NULL;
        }
 
        if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f900fae..239cea7 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -750,7 +750,7 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
 
        BUG_ON(len > skb->len);
 
-       tcp_clear_all_retrans_hints(tp);
+       tcp_clear_retrans_hints_partial(tp);
        nsize = skb_headlen(skb) - len;
        if (nsize < 0)
                nsize = 0;
@@ -1823,7 +1823,9 @@ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb,
        tp->packets_out -= tcp_skb_pcount(next_skb);
 
        /* changed transmit queue under us so clear hints */
-       tcp_clear_all_retrans_hints(tp);
+       tcp_clear_retrans_hints_partial(tp);
+       if (next_skb == tp->retransmit_skb_hint)
+               tp->retransmit_skb_hint = skb;
 
        sk_wmem_free_skb(sk, next_skb);
 }
@@ -1853,7 +1855,7 @@ void tcp_simple_retransmit(struct sock *sk)
                }
        }
 
-       tcp_clear_all_retrans_hints(tp);
+       tcp_clear_retrans_hints_partial(tp);
 
        if (prior_lost == tp->lost_out)
                return;