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authorYuchung Cheng <ycheng@google.com>2011-03-14 10:57:03 +0000
committerDavid S. Miller <davem@davemloft.net>2011-03-22 19:36:08 -0700
commit67d4120a1793138bc9f4a6eb61d0fc5298ed97e0 (patch)
tree24ffa212d26a6048675a2b7f2c1a4371e62c9f6d
parenta7bff75b087e7a355838a32efe61707cfa73c194 (diff)
tcp: avoid cwnd moderation in undo
In the current undo logic, cwnd is moderated after it was restored to the value prior entering fast-recovery. It was moderated first in tcp_try_undo_recovery then again in tcp_complete_cwr. Since the undo indicates recovery was false, these moderations are not necessary. If the undo is triggered when most of the outstanding data have been acknowledged, the (restored) cwnd is falsely pulled down to a small value. This patch removes these cwnd moderations if cwnd is undone a) during fast-recovery b) by receiving DSACKs past fast-recovery Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv4/tcp_input.c12
1 files changed, 7 insertions, 5 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index da782e7ab16d..e72af7e31d1c 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2659,7 +2659,7 @@ static void DBGUNDO(struct sock *sk, const char *msg)
#define DBGUNDO(x...) do { } while (0)
#endif
-static void tcp_undo_cwr(struct sock *sk, const int undo)
+static void tcp_undo_cwr(struct sock *sk, const int undo_ssthresh)
{
struct tcp_sock *tp = tcp_sk(sk);
@@ -2671,14 +2671,13 @@ static void tcp_undo_cwr(struct sock *sk, const int undo)
else
tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1);
- if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
+ if (undo_ssthresh && tp->prior_ssthresh > tp->snd_ssthresh) {
tp->snd_ssthresh = tp->prior_ssthresh;
TCP_ECN_withdraw_cwr(tp);
}
} else {
tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
}
- tcp_moderate_cwnd(tp);
tp->snd_cwnd_stamp = tcp_time_stamp;
}
@@ -2822,8 +2821,11 @@ static int tcp_try_undo_loss(struct sock *sk)
static inline void tcp_complete_cwr(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);
- tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
- tp->snd_cwnd_stamp = tcp_time_stamp;
+ /* Do not moderate cwnd if it's already undone in cwr or recovery */
+ if (tp->undo_marker && tp->snd_cwnd > tp->snd_ssthresh) {
+ tp->snd_cwnd = tp->snd_ssthresh;
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+ }
tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
}