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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/tcp_cong.c
parent071d5080e33d6f24139e4213c2d9f97a2c21b602 (diff)
downloadlinux-76174004a0f19785a328f40388e87e982bbf69b9.tar.bz2
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/tcp_cong.c')
-rw-r--r--net/ipv4/tcp_cong.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 654729a8cb23..a2ed23c595cf 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);