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Commit fb998862 authored by Kevin Yang's avatar Kevin Yang Committed by David S. Miller
Browse files

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: 0f8782ea ("tcp_bbr: add BBR congestion control")
Signed-off-by: default avatarKevin Yang <yyd@google.com>
Signed-off-by: default avatarNeal Cardwell <ncardwell@google.com>
Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
Reviewed-by: default avatarSoheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 431280ee

net/ipv4/tcp_bbr.c

+18 −16
Original line number Diff line number Diff line
@@ -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;