[DCCP] CCID2: Code optimizations

These are code optimizations which are relevant when dealing with large
windows.  They are not coded the way I would like to, but they do the job for
the short-term.  This patch should be more neat.

Commiter note: Changed the seqno comparisions to use {after,before}48 to handle
               wrapping.

Signed-off-by: Andrea Bittau <a.bittau@cs.ucl.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>

2 files changed, 21 insertions, 2 deletions

diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index 162032baeac0..6533cb2f27bb 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -619,7 +619,17 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
         }
 
         ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
-        seqp = hctx->ccid2hctx_seqh->ccid2s_prev;
+        if (after48(ackno, hctx->ccid2hctx_high_ack))
+                hctx->ccid2hctx_high_ack = ackno;
+
+        seqp = hctx->ccid2hctx_seqt;
+        while (before48(seqp->ccid2s_seq, ackno)) {
+                seqp = seqp->ccid2s_next;
+                if (seqp == hctx->ccid2hctx_seqh) {
+                        seqp = hctx->ccid2hctx_seqh->ccid2s_prev;
+                        break;
+                }
+        }
 
         /* If in slow-start, cwnd can increase at most Ack Ratio / 2 packets for
          * this single ack.  I round up.
@@ -697,7 +707,14 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
         /* The state about what is acked should be correct now
          * Check for NUMDUPACK
          */
-        seqp = hctx->ccid2hctx_seqh->ccid2s_prev;
+        seqp = hctx->ccid2hctx_seqt;
+        while (before48(seqp->ccid2s_seq, hctx->ccid2hctx_high_ack)) {
+                seqp = seqp->ccid2s_next;
+                if (seqp == hctx->ccid2hctx_seqh) {
+                        seqp = hctx->ccid2hctx_seqh->ccid2s_prev;
+                        break;
+                }
+        }
         done = 0;
         while (1) {
                 if (seqp->ccid2s_acked) {
@@ -771,6 +788,7 @@ static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
         hctx->ccid2hctx_lastrtt  = 0;
         hctx->ccid2hctx_rpdupack = -1;
         hctx->ccid2hctx_last_cong = jiffies;
+        hctx->ccid2hctx_high_ack = 0;
 
         hctx->ccid2hctx_rtotimer.function = &ccid2_hc_tx_rto_expire;
         hctx->ccid2hctx_rtotimer.data     = (unsigned long)sk;
diff --git a/net/dccp/ccids/ccid2.h b/net/dccp/ccids/ccid2.h
index 5b2ef4acb300..a97a89927308 100644
--- a/net/dccp/ccids/ccid2.h
+++ b/net/dccp/ccids/ccid2.h
@@ -72,6 +72,7 @@ struct ccid2_hc_tx_sock {
         int                     ccid2hctx_rpdupack;
         int                     ccid2hctx_sendwait;
         unsigned long           ccid2hctx_last_cong;
+        u64                     ccid2hctx_high_ack;
 };
 
 struct ccid2_hc_rx_sock {