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Date: Fri, 5 May 2017 12:53:23 -0700
From: Wei Wang <weiwan@...gle.com>
To: David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Cc: Yuchung Cheng <ycheng@...gle.com>,
Neal Cardwell <ncardwell@...gle.com>,
Eric Dumazet <edumazet@...gle.com>,
Wei Wang <weiwan@...gle.com>
Subject: [PATCH net] tcp: make congestion control optionally skip slow start after idle
From: Wei Wang <weiwan@...gle.com>
Congestion control modules that want full control over congestion
control behavior do not want the cwnd modifications controlled by
the sysctl_tcp_slow_start_after_idle code path.
So skip those code paths for CC modules that use the cong_control()
API.
As an example, those cwnd effects are not desired for the BBR congestion
control algorithm.
Fixes: c0402760f565 ("tcp: new CC hook to set sending rate with rate_sample in any CA state")
Signed-off-by: Wei Wang <weiwan@...gle.com>
Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
---
include/net/tcp.h | 4 +++-
net/ipv4/tcp_output.c | 4 +++-
2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 270e5cc43c99..4e16486802fc 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1234,10 +1234,12 @@ void tcp_cwnd_restart(struct sock *sk, s32 delta);
static inline void tcp_slow_start_after_idle_check(struct sock *sk)
{
+ const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
struct tcp_sock *tp = tcp_sk(sk);
s32 delta;
- if (!sysctl_tcp_slow_start_after_idle || tp->packets_out)
+ if (!sysctl_tcp_slow_start_after_idle || tp->packets_out ||
+ ca_ops->cong_control)
return;
delta = tcp_time_stamp - tp->lsndtime;
if (delta > inet_csk(sk)->icsk_rto)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 60111a0fc201..4858e190f6ac 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1514,6 +1514,7 @@ static void tcp_cwnd_application_limited(struct sock *sk)
static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
{
+ const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
struct tcp_sock *tp = tcp_sk(sk);
/* Track the maximum number of outstanding packets in each
@@ -1536,7 +1537,8 @@ static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
tp->snd_cwnd_used = tp->packets_out;
if (sysctl_tcp_slow_start_after_idle &&
- (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
+ (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
+ !ca_ops->cong_control)
tcp_cwnd_application_limited(sk);
/* The following conditions together indicate the starvation
--
2.13.0.rc1.294.g07d810a77f-goog
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