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tcp_bbr: add bbr_check_probe_rtt_done() helper 

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: 0f8782ea14 ("tcp_bbr: add BBR congestion control")
Signed-off-by: Kevin Yang <yyd@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Reviewed-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Kevin Yang 2018-08-22 17:43:14 -04:00 committed by David S. Miller
parent 431280eebe
commit fb99886224
1 changed files with 18 additions and 16 deletions
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34
net/ipv4/tcp_bbr.c
View File

@ -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;