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Commit 018da8f4 authored by Stephen Hemminger's avatar Stephen Hemminger Committed by David S. Miller
Browse files

[TCP] BIC: remove low utilization code. 

The latest BICTCP patch at:
http://www.csc.ncsu.edu:8080/faculty/rhee/export/bitcp/index_files/Page546.htm



disables the low_utilization feature of BICTCP because it doesn't work
in some cases. This patch removes it.

Signed-off-by: default avatarStephen Hemminger <shemminger@osdl.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent d28d1e08

net/ipv4/tcp_bic.c

+1 −80
Original line number Diff line number Diff line
@@ -30,8 +30,6 @@ static int fast_convergence = 1; 
static int max_increment = 16;

static int low_window = 14;

static int beta = 819;		/* = 819/1024 (BICTCP_BETA_SCALE) */

static int low_utilization_threshold = 153;

static int low_utilization_period = 2;

static int initial_ssthresh = 100;

static int smooth_part = 20;
@@ -43,10 +41,6 @@ module_param(low_window, int, 0644); 
MODULE_PARM_DESC(low_window, "lower bound on congestion window (for TCP friendliness)");

module_param(beta, int, 0644);

MODULE_PARM_DESC(beta, "beta for multiplicative increase");

module_param(low_utilization_threshold, int, 0644);

MODULE_PARM_DESC(low_utilization_threshold, "percent (scaled by 1024) for low utilization mode");

module_param(low_utilization_period, int, 0644);

MODULE_PARM_DESC(low_utilization_period, "if average delay exceeds then goto to low utilization mode (seconds)");

module_param(initial_ssthresh, int, 0644);

MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold");

module_param(smooth_part, int, 0644);
@@ -60,11 +54,6 @@ struct bictcp { 
	u32	loss_cwnd;	/* congestion window at last loss */

	u32	last_cwnd;	/* the last snd_cwnd */

	u32	last_time;	/* time when updated last_cwnd */

	u32	delay_min;	/* min delay */

	u32	delay_max;	/* max delay */

	u32	last_delay;

	u8	low_utilization;/* 0: high; 1: low */

	u32	low_utilization_start;	/* starting time of low utilization detection*/

	u32	epoch_start;	/* beginning of an epoch */

#define ACK_RATIO_SHIFT	4

	u32	delayed_ack;	/* estimate the ratio of Packets/ACKs << 4 */
@@ -77,11 +66,6 @@ static inline void bictcp_reset(struct bictcp *ca) 
	ca->loss_cwnd = 0;

	ca->last_cwnd = 0;

	ca->last_time = 0;

	ca->delay_min = 0;

	ca->delay_max = 0;

	ca->last_delay = 0;

	ca->low_utilization = 0;

	ca->low_utilization_start = 0;

	ca->epoch_start = 0;

	ca->delayed_ack = 2 << ACK_RATIO_SHIFT;

}
@@ -143,8 +127,7 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd) 
	}



	/* if in slow start or link utilization is very low */

	if ( ca->loss_cwnd == 0 ||

	     (cwnd > ca->loss_cwnd && ca->low_utilization)) {

	if (ca->loss_cwnd == 0) {

		if (ca->cnt > 20) /* increase cwnd 5% per RTT */

			ca->cnt = 20;

	}
@@ -154,69 +137,12 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd) 
		ca->cnt = 1;

}





/* Detect low utilization in congestion avoidance */

static inline void bictcp_low_utilization(struct sock *sk, int flag)

{

	const struct tcp_sock *tp = tcp_sk(sk);

	struct bictcp *ca = inet_csk_ca(sk);

	u32 dist, delay;



	/* No time stamp */

	if (!(tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) ||

	     /* Discard delay samples right after fast recovery */

	     tcp_time_stamp < ca->epoch_start + HZ ||

	     /* this delay samples may not be accurate */

	     flag == 0) {

		ca->last_delay = 0;

		goto notlow;

	}



	delay = ca->last_delay<<3;	/* use the same scale as tp->srtt*/

	ca->last_delay = tcp_time_stamp - tp->rx_opt.rcv_tsecr;

	if (delay == 0) 		/* no previous delay sample */

		goto notlow;



	/* first time call or link delay decreases */

	if (ca->delay_min == 0 || ca->delay_min > delay) {

		ca->delay_min = ca->delay_max = delay;

		goto notlow;

	}



	if (ca->delay_max < delay)

		ca->delay_max = delay;



	/* utilization is low, if avg delay < dist*threshold

	   for checking_period time */

	dist = ca->delay_max - ca->delay_min;

	if (dist <= ca->delay_min>>6 ||

	    tp->srtt - ca->delay_min >=  (dist*low_utilization_threshold)>>10)

		goto notlow;



	if (ca->low_utilization_start == 0) {

		ca->low_utilization = 0;

		ca->low_utilization_start = tcp_time_stamp;

	} else if ((s32)(tcp_time_stamp - ca->low_utilization_start)

			> low_utilization_period*HZ) {

		ca->low_utilization = 1;

	}



	return;



 notlow:

	ca->low_utilization = 0;

	ca->low_utilization_start = 0;



}



static void bictcp_cong_avoid(struct sock *sk, u32 ack,

			      u32 seq_rtt, u32 in_flight, int data_acked)

{

	struct tcp_sock *tp = tcp_sk(sk);

	struct bictcp *ca = inet_csk_ca(sk);



	bictcp_low_utilization(sk, data_acked);



	if (!tcp_is_cwnd_limited(sk, in_flight))

		return;
@@ -249,11 +175,6 @@ static u32 bictcp_recalc_ssthresh(struct sock *sk) 


	ca->epoch_start = 0;	/* end of epoch */



	/* in case of wrong delay_max*/

	if (ca->delay_min > 0 && ca->delay_max > ca->delay_min)

		ca->delay_max = ca->delay_min

			+ ((ca->delay_max - ca->delay_min)* 90) / 100;



	/* Wmax and fast convergence */

	if (tp->snd_cwnd < ca->last_max_cwnd && fast_convergence)

		ca->last_max_cwnd = (tp->snd_cwnd * (BICTCP_BETA_SCALE + beta))