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>

2 files changed, 8 insertions, 4 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d017aed6edd7..44a4fffc2cc3 100644
--- 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 f900fae8b87e..239cea7b6c0e 100644
--- 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;