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Release 4.11 net/ipv4/tcp_bic.c

Directory: net/ipv4
/*
 * Binary Increase Congestion control for TCP
 * Home page:
 *      http://netsrv.csc.ncsu.edu/twiki/bin/view/Main/BIC
 * This is from the implementation of BICTCP in
 * Lison-Xu, Kahaled Harfoush, and Injong Rhee.
 *  "Binary Increase Congestion Control for Fast, Long Distance
 *  Networks" in InfoComm 2004
 * Available from:
 *  http://netsrv.csc.ncsu.edu/export/bitcp.pdf
 *
 * Unless BIC is enabled and congestion window is large
 * this behaves the same as the original Reno.
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <net/tcp.h>


#define BICTCP_BETA_SCALE    1024	
/* Scale factor beta calculation
                                         * max_cwnd = snd_cwnd * beta
                                         */

#define BICTCP_B		4	 
/*
                                          * In binary search,
                                          * go to point (max+min)/N
                                          */


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 initial_ssthresh;

static int smooth_part = 20;

module_param(fast_convergence, int, 0644);
MODULE_PARM_DESC(fast_convergence, "turn on/off fast convergence");
module_param(max_increment, int, 0644);
MODULE_PARM_DESC(max_increment, "Limit on increment allowed during binary search");
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(initial_ssthresh, int, 0644);
MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold");
module_param(smooth_part, int, 0644);
MODULE_PARM_DESC(smooth_part, "log(B/(B*Smin))/log(B/(B-1))+B, # of RTT from Wmax-B to Wmax");

/* BIC TCP Parameters */

struct bictcp {
	
u32	cnt;		/* increase cwnd by 1 after ACKs */
	
u32	last_max_cwnd;	/* last maximum snd_cwnd */
	
u32	loss_cwnd;	/* congestion window at last loss */
	
u32	last_cwnd;	/* the last snd_cwnd */
	
u32	last_time;	/* time when updated last_cwnd */
	
u32	epoch_start;	/* beginning of an epoch */

#define ACK_RATIO_SHIFT	4
	
u32	delayed_ack;	/* estimate the ratio of Packets/ACKs << 4 */
};


static inline void bictcp_reset(struct bictcp *ca) { ca->cnt = 0; ca->last_max_cwnd = 0; ca->last_cwnd = 0; ca->last_time = 0; ca->epoch_start = 0; ca->delayed_ack = 2 << ACK_RATIO_SHIFT; }

Contributors

PersonTokensPropCommitsCommitProp
Stephen Hemminger50100.00%1100.00%
Total50100.00%1100.00%


static void bictcp_init(struct sock *sk) { struct bictcp *ca = inet_csk_ca(sk); bictcp_reset(ca); ca->loss_cwnd = 0; if (initial_ssthresh) tcp_sk(sk)->snd_ssthresh = initial_ssthresh; }

Contributors

PersonTokensPropCommitsCommitProp
Stephen Hemminger2248.89%133.33%
Neal Cardwell1533.33%133.33%
Arnaldo Carvalho de Melo817.78%133.33%
Total45100.00%3100.00%

/* * Compute congestion window to use. */
static inline void bictcp_update(struct bictcp *ca, u32 cwnd) { if (ca->last_cwnd == cwnd && (s32)(tcp_time_stamp - ca->last_time) <= HZ / 32) return; ca->last_cwnd = cwnd; ca->last_time = tcp_time_stamp; if (ca->epoch_start == 0) /* record the beginning of an epoch */ ca->epoch_start = tcp_time_stamp; /* start off normal */ if (cwnd <= low_window) { ca->cnt = cwnd; return; } /* binary increase */ if (cwnd < ca->last_max_cwnd) { __u32 dist = (ca->last_max_cwnd - cwnd) / BICTCP_B; if (dist > max_increment) /* linear increase */ ca->cnt = cwnd / max_increment; else if (dist <= 1U) /* binary search increase */ ca->cnt = (cwnd * smooth_part) / BICTCP_B; else /* binary search increase */ ca->cnt = cwnd / dist; } else { /* slow start AMD linear increase */ if (cwnd < ca->last_max_cwnd + BICTCP_B) /* slow start */ ca->cnt = (cwnd * smooth_part) / BICTCP_B; else if (cwnd < ca->last_max_cwnd + max_increment*(BICTCP_B-1)) /* slow start */ ca->cnt = (cwnd * (BICTCP_B-1)) / (cwnd - ca->last_max_cwnd); else /* linear increase */ ca->cnt = cwnd / max_increment; } /* if in slow start or link utilization is very low */ if (ca->last_max_cwnd == 0) { if (ca->cnt > 20) /* increase cwnd 5% per RTT */ ca->cnt = 20; } ca->cnt = (ca->cnt << ACK_RATIO_SHIFT) / ca->delayed_ack; if (ca->cnt == 0) /* cannot be zero */ ca->cnt = 1; }

Contributors

PersonTokensPropCommitsCommitProp
Stephen Hemminger28499.65%266.67%
Neal Cardwell10.35%133.33%
Total285100.00%3100.00%


static void bictcp_cong_avoid(struct sock *sk, u32 ack, u32 acked) { struct tcp_sock *tp = tcp_sk(sk); struct bictcp *ca = inet_csk_ca(sk); if (!tcp_is_cwnd_limited(sk)) return; if (tcp_in_slow_start(tp)) tcp_slow_start(tp, acked); else { bictcp_update(ca, tp->snd_cwnd); tcp_cong_avoid_ai(tp, ca->cnt, 1); } }

Contributors

PersonTokensPropCommitsCommitProp
Stephen Hemminger5768.67%337.50%
Arnaldo Carvalho de Melo1416.87%112.50%
Yuchung Cheng67.23%225.00%
Ilpo Järvinen44.82%112.50%
Neal Cardwell22.41%112.50%
Total83100.00%8100.00%

/* * behave like Reno until low_window is reached, * then increase congestion window slowly */
static u32 bictcp_recalc_ssthresh(struct sock *sk) { const struct tcp_sock *tp = tcp_sk(sk); struct bictcp *ca = inet_csk_ca(sk); ca->epoch_start = 0; /* end of epoch */ /* 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)) / (2 * BICTCP_BETA_SCALE); else ca->last_max_cwnd = tp->snd_cwnd; ca->loss_cwnd = tp->snd_cwnd; if (tp->snd_cwnd <= low_window) return max(tp->snd_cwnd >> 1U, 2U); else return max((tp->snd_cwnd * beta) / BICTCP_BETA_SCALE, 2U); }

Contributors

PersonTokensPropCommitsCommitProp
Stephen Hemminger11388.28%150.00%
Arnaldo Carvalho de Melo1511.72%150.00%
Total128100.00%2100.00%


static u32 bictcp_undo_cwnd(struct sock *sk) { const struct tcp_sock *tp = tcp_sk(sk); const struct bictcp *ca = inet_csk_ca(sk); return max(tp->snd_cwnd, ca->loss_cwnd); }

Contributors

PersonTokensPropCommitsCommitProp
Stephen Hemminger2862.22%133.33%
Arnaldo Carvalho de Melo1635.56%133.33%
Neal Cardwell12.22%133.33%
Total45100.00%3100.00%


static void bictcp_state(struct sock *sk, u8 new_state) { if (new_state == TCP_CA_Loss) bictcp_reset(inet_csk_ca(sk)); }

Contributors

PersonTokensPropCommitsCommitProp
Stephen Hemminger2485.71%150.00%
Arnaldo Carvalho de Melo414.29%150.00%
Total28100.00%2100.00%

/* Track delayed acknowledgment ratio using sliding window * ratio = (15*ratio + sample) / 16 */
static void bictcp_acked(struct sock *sk, const struct ack_sample *sample) { const struct inet_connection_sock *icsk = inet_csk(sk); if (icsk->icsk_ca_state == TCP_CA_Open) { struct bictcp *ca = inet_csk_ca(sk); ca->delayed_ack += sample->pkts_acked - (ca->delayed_ack >> ACK_RATIO_SHIFT); } }

Contributors

PersonTokensPropCommitsCommitProp
Stephen Hemminger3351.56%133.33%
Arnaldo Carvalho de Melo1726.56%133.33%
Lawrence Brakmo1421.88%133.33%
Total64100.00%3100.00%

static struct tcp_congestion_ops bictcp __read_mostly = { .init = bictcp_init, .ssthresh = bictcp_recalc_ssthresh, .cong_avoid = bictcp_cong_avoid, .set_state = bictcp_state, .undo_cwnd = bictcp_undo_cwnd, .pkts_acked = bictcp_acked, .owner = THIS_MODULE, .name = "bic", };
static int __init bictcp_register(void) { BUILD_BUG_ON(sizeof(struct bictcp) > ICSK_CA_PRIV_SIZE); return tcp_register_congestion_control(&bictcp); }

Contributors

PersonTokensPropCommitsCommitProp
Stephen Hemminger2592.59%133.33%
Alexey Dobriyan13.70%133.33%
Arnaldo Carvalho de Melo13.70%133.33%
Total27100.00%3100.00%


static void __exit bictcp_unregister(void) { tcp_unregister_congestion_control(&bictcp); }

Contributors

PersonTokensPropCommitsCommitProp
Stephen Hemminger15100.00%1100.00%
Total15100.00%1100.00%

module_init(bictcp_register); module_exit(bictcp_unregister); MODULE_AUTHOR("Stephen Hemminger"); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("BIC TCP");

Overall Contributors

PersonTokensPropCommitsCommitProp
Stephen Hemminger91588.41%743.75%
Arnaldo Carvalho de Melo757.25%16.25%
Neal Cardwell191.84%212.50%
Lawrence Brakmo141.35%16.25%
Yuchung Cheng60.58%212.50%
Ilpo Järvinen40.39%16.25%
Alexey Dobriyan10.10%16.25%
Sangtae Ha10.10%16.25%
Total1035100.00%16100.00%
Directory: net/ipv4
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