summaryrefslogtreecommitdiffstats
path: root/net/ipv4
diff options
context:
space:
mode:
authorYuchung Cheng <ycheng@google.com>2015-07-09 13:16:30 -0700
committerDavid S. Miller <davem@davemloft.net>2015-07-09 14:22:52 -0700
commit76174004a0f19785a328f40388e87e982bbf69b9 (patch)
tree113a691ab55819f20b367cdeb8ba86440aa62177 /net/ipv4
parent071d5080e33d6f24139e4213c2d9f97a2c21b602 (diff)
downloadop-kernel-dev-76174004a0f19785a328f40388e87e982bbf69b9.zip
op-kernel-dev-76174004a0f19785a328f40388e87e982bbf69b9.tar.gz
tcp: do not slow start when cwnd equals ssthresh
In the original design slow start is only used to raise cwnd when cwnd is stricly below ssthresh. It makes little sense to slow start when cwnd == ssthresh: especially when hystart has set ssthresh in the initial ramp, or after recovery when cwnd resets to ssthresh. Not doing so will also help reduce the buffer bloat slightly. Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Nandita Dukkipati <nanditad@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
-rw-r--r--net/ipv4/tcp_cdg.c2
-rw-r--r--net/ipv4/tcp_cong.c4
-rw-r--r--net/ipv4/tcp_hybla.c2
3 files changed, 3 insertions, 5 deletions
diff --git a/net/ipv4/tcp_cdg.c b/net/ipv4/tcp_cdg.c
index 8c6fd3d..167b6a3 100644
--- a/net/ipv4/tcp_cdg.c
+++ b/net/ipv4/tcp_cdg.c
@@ -264,7 +264,7 @@ static void tcp_cdg_cong_avoid(struct sock *sk, u32 ack, u32 acked)
u32 prior_snd_cwnd;
u32 incr;
- if (tp->snd_cwnd < tp->snd_ssthresh && hystart_detect)
+ if (tcp_in_slow_start(tp) && hystart_detect)
tcp_cdg_hystart_update(sk);
if (after(ack, ca->rtt_seq) && ca->rtt.v64) {
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 654729a..a2ed23c 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -365,10 +365,8 @@ int tcp_set_congestion_control(struct sock *sk, const char *name)
*/
u32 tcp_slow_start(struct tcp_sock *tp, u32 acked)
{
- u32 cwnd = tp->snd_cwnd + acked;
+ u32 cwnd = min(tp->snd_cwnd + acked, tp->snd_ssthresh);
- if (cwnd > tp->snd_ssthresh)
- cwnd = tp->snd_ssthresh + 1;
acked -= cwnd - tp->snd_cwnd;
tp->snd_cwnd = min(cwnd, tp->snd_cwnd_clamp);
diff --git a/net/ipv4/tcp_hybla.c b/net/ipv4/tcp_hybla.c
index f963b27..083831e 100644
--- a/net/ipv4/tcp_hybla.c
+++ b/net/ipv4/tcp_hybla.c
@@ -112,7 +112,7 @@ static void hybla_cong_avoid(struct sock *sk, u32 ack, u32 acked)
rho_fractions = ca->rho_3ls - (ca->rho << 3);
- if (tp->snd_cwnd < tp->snd_ssthresh) {
+ if (tcp_in_slow_start(tp)) {
/*
* slow start
* INC = 2^RHO - 1
OpenPOWER on IntegriCloud