[TCP]: Avoid clearing sacktag hint in trivial situations

There's no reason to clear the sacktag skb hint when small part
of the rexmit queue changes. Account changes (if any) instead when
fragmenting/collapsing. RTO/FRTO do not touch SACKED_ACKED bits so
no need to discard SACK tag hint at all.

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 d78ad9bfcfa7e09dbb2cd7a66119f7cead378b96..456983d1fcec80f327ec7994eccedecba668c6dd 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1067,11 +1067,15 @@ static inline void tcp_mib_init(void)
 }
 
 /* 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;
        tp->retransmit_skb_hint = NULL;
        tp->forward_skb_hint = NULL;
+}
+
+static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp) {
+       tcp_clear_retrans_hints_partial(tp);
        tp->fastpath_skb_hint = NULL;
 }
 

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 65b9f274a7741842463f8f2f51a21c70350069ff..4c10d9cad20f594e2bd6a3a15b0c6d45554ece38 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1671,7 +1671,7 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
        tp->high_seq = tp->frto_highmark;
        TCP_ECN_queue_cwr(tp);
 
-       tcp_clear_all_retrans_hints(tp);
+       tcp_clear_retrans_hints_partial(tp);
 }
 
 void tcp_clear_retrans(struct tcp_sock *tp)
@@ -1711,10 +1711,14 @@ void tcp_enter_loss(struct sock *sk, int how)
        tp->bytes_acked = 0;
        tcp_clear_retrans(tp);
 
-       /* Push undo marker, if it was plain RTO and nothing
-        * was retransmitted. */
-       if (!how)
+       if (!how) {
+               /* Push undo marker, if it was plain RTO and nothing
+                * was retransmitted. */
                tp->undo_marker = tp->snd_una;
+               tcp_clear_retrans_hints_partial(tp);
+       } else {
+               tcp_clear_all_retrans_hints(tp);
+       }
 
        tcp_for_write_queue(skb, sk) {
                if (skb == tcp_send_head(sk))
@@ -1741,8 +1745,6 @@ void tcp_enter_loss(struct sock *sk, int how)
        TCP_ECN_queue_cwr(tp);
        /* Abort FRTO algorithm if one is in progress */
        tp->frto_counter = 0;
-
-       tcp_clear_all_retrans_hints(tp);
 }
 
 static int tcp_check_sack_reneging(struct sock *sk)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f46d24b8410fc771288779387309143fbeed88e4..cbb83acd830a89009ae88f522551340bcd267399 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -687,7 +687,7 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss
 
        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;
@@ -1718,9 +1718,6 @@ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, int m
                BUG_ON(tcp_skb_pcount(skb) != 1 ||
                       tcp_skb_pcount(next_skb) != 1);
 
-               /* changing transmit queue under us so clear hints */
-               tcp_clear_all_retrans_hints(tp);
-
                /* Ok.  We will be able to collapse the packet. */
                tcp_unlink_write_queue(next_skb, sk);
 
@@ -1759,6 +1756,13 @@ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, int m
 
                tcp_adjust_fackets_out(tp, skb, tcp_skb_pcount(next_skb));
                tp->packets_out -= tcp_skb_pcount(next_skb);
+
+               /* changed transmit queue under us so clear hints */
+               tcp_clear_retrans_hints_partial(tp);
+               /* manually tune sacktag skb hint */
+               if (tp->fastpath_skb_hint == next_skb)
+                       tp->fastpath_skb_hint = skb;
+
                sk_stream_free_skb(sk, next_skb);
        }
 }