This patch add a helper function bbr_check_probe_rtt_done() to
1. check the condition to see if bbr should exit probe_rtt mode;
2. process the logic of exiting probe_rtt mode.
Fixes: 0f8782ea1497 ("tcp_bbr: add BBR congestion control")
Signed-off-by: Kevin Yang <y...@google.com>
Signed-off-by: Neal Cardwell <ncardw...@google.com>
Signed-off-by: Yuchung Cheng <ych...@google.com>
Reviewed-by: Soheil Hassas Yeganeh <soh...@google.com>
---
net/ipv4/tcp_bbr.c | 34 ++++++++++++++++++----------------
1 file changed, 18 insertions(+), 16 deletions(-)
diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c
index 13d34427ca3dd..fd7bccf36a263 100644
--- a/net/ipv4/tcp_bbr.c
+++ b/net/ipv4/tcp_bbr.c
@@ -95,11 +95,10 @@ struct bbr {
u32 mode:3, /* current bbr_mode in state machine */
prev_ca_state:3, /* CA state on previous ACK */
packet_conservation:1, /* use packet conservation? */
- restore_cwnd:1, /* decided to revert cwnd to old value */
round_start:1, /* start of packet-timed tx->ack round? */
idle_restart:1, /* restarting after idle? */
probe_rtt_round_done:1, /* a BBR_PROBE_RTT round at 4 pkts? */
- unused:12,
+ unused:13,
lt_is_sampling:1, /* taking long-term ("LT") samples now? */
lt_rtt_cnt:7, /* round trips in long-term interval */
lt_use_bw:1; /* use lt_bw as our bw estimate? */
@@ -396,17 +395,11 @@ static bool bbr_set_cwnd_to_recover_or_restore(
cwnd = tcp_packets_in_flight(tp) + acked;
} else if (prev_state >= TCP_CA_Recovery && state < TCP_CA_Recovery) {
/* Exiting loss recovery; restore cwnd saved before recovery. */
- bbr->restore_cwnd = 1;
+ cwnd = max(cwnd, bbr->prior_cwnd);
bbr->packet_conservation = 0;
}
bbr->prev_ca_state = state;
- if (bbr->restore_cwnd) {
- /* Restore cwnd after exiting loss recovery or PROBE_RTT. */
- cwnd = max(cwnd, bbr->prior_cwnd);
- bbr->restore_cwnd = 0;
- }
-
if (bbr->packet_conservation) {
*new_cwnd = max(cwnd, tcp_packets_in_flight(tp) + acked);
return true; /* yes, using packet conservation */
@@ -748,6 +741,20 @@ static void bbr_check_drain(struct sock *sk, const struct
rate_sample *rs)
bbr_reset_probe_bw_mode(sk); /* we estimate queue is drained */
}
+static void bbr_check_probe_rtt_done(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct bbr *bbr = inet_csk_ca(sk);
+
+ if (!(bbr->probe_rtt_done_stamp &&
+ after(tcp_jiffies32, bbr->probe_rtt_done_stamp)))
+ return;
+
+ bbr->min_rtt_stamp = tcp_jiffies32; /* wait a while until PROBE_RTT */
+ tp->snd_cwnd = max(tp->snd_cwnd, bbr->prior_cwnd);
+ bbr_reset_mode(sk);
+}
+
/* The goal of PROBE_RTT mode is to have BBR flows cooperatively and
* periodically drain the bottleneck queue, to converge to measure the true
* min_rtt (unloaded propagation delay). This allows the flows to keep queues
@@ -806,12 +813,8 @@ static void bbr_update_min_rtt(struct sock *sk, const
struct rate_sample *rs)
} else if (bbr->probe_rtt_done_stamp) {
if (bbr->round_start)
bbr->probe_rtt_round_done = 1;
- if (bbr->probe_rtt_round_done &&
- after(tcp_jiffies32, bbr->probe_rtt_done_stamp)) {
- bbr->min_rtt_stamp = tcp_jiffies32;
- bbr->restore_cwnd = 1; /* snap to prior_cwnd */
- bbr_reset_mode(sk);
- }
+ if (bbr->probe_rtt_round_done)
+ bbr_check_probe_rtt_done(sk);
}
}
/* Restart after idle ends only once we process a new S/ACK for data */
@@ -862,7 +865,6 @@ static void bbr_init(struct sock *sk)
bbr->has_seen_rtt = 0;
bbr_init_pacing_rate_from_rtt(sk);
- bbr->restore_cwnd = 0;
bbr->round_start = 0;
bbr->idle_restart = 0;
bbr->full_bw_reached = 0;
--
2.18.0.1017.ga543ac7ca45-goog
