[mirror_ubuntu-jammy-kernel.git] / net / ipv4 / tcp_bic.c

/*
 * Binary Increase Congestion control for TCP
 *
 * 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://www.csc.ncsu.edu/faculty/rhee/export/bitcp.pdf
 *
 * Unless BIC is enabled and congestion window is large
 * this behaves the same as the original Reno.
 */

#include <linux/config.h>
#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 = 32;
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;

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(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);
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	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 */
};

static inline void bictcp_reset(struct bictcp *ca)
{
	ca->cnt = 0;
	ca->last_max_cwnd = 0;
	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;
}

static void bictcp_init(struct tcp_sock *tp)
{
	bictcp_reset(tcp_ca(tp));
	if (initial_ssthresh)
		tp->snd_ssthresh = initial_ssthresh;
}

/*
 * 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->loss_cwnd == 0 ||
	     (cwnd > ca->loss_cwnd && ca->low_utilization)) {
		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;
}


/* Detect low utilization in congestion avoidance */
static inline void bictcp_low_utilization(struct tcp_sock *tp, int flag)
{
	struct bictcp *ca = tcp_ca(tp);
	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 tcp_sock *tp, u32 ack,
			      u32 seq_rtt, u32 in_flight, int data_acked)
{
	struct bictcp *ca = tcp_ca(tp);

	bictcp_low_utilization(tp, data_acked);

	if (in_flight < tp->snd_cwnd)
		return;

	if (tp->snd_cwnd <= tp->snd_ssthresh) {
		/* In "safe" area, increase. */
		if (tp->snd_cwnd < tp->snd_cwnd_clamp)
			tp->snd_cwnd++;
	} else {
		bictcp_update(ca, tp->snd_cwnd);

                /* In dangerous area, increase slowly.
		 * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
		 */
		if (tp->snd_cwnd_cnt >= ca->cnt) {
			if (tp->snd_cwnd < tp->snd_cwnd_clamp)
				tp->snd_cwnd++;
			tp->snd_cwnd_cnt = 0;
		} else
			tp->snd_cwnd_cnt++;
	}

}

/*
 *	behave like Reno until low_window is reached,
 *	then increase congestion window slowly
 */
static u32 bictcp_recalc_ssthresh(struct tcp_sock *tp)
{
	struct bictcp *ca = tcp_ca(tp);

	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))
			/ (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);
}

static u32 bictcp_undo_cwnd(struct tcp_sock *tp)
{
	struct bictcp *ca = tcp_ca(tp);

	return max(tp->snd_cwnd, ca->last_max_cwnd);
}

static u32 bictcp_min_cwnd(struct tcp_sock *tp)
{
	return tp->snd_ssthresh;
}

static void bictcp_state(struct tcp_sock *tp, u8 new_state)
{
	if (new_state == TCP_CA_Loss)
		bictcp_reset(tcp_ca(tp));
}

/* Track delayed acknowledgement ratio using sliding window
 * ratio = (15*ratio + sample) / 16
 */
static void bictcp_acked(struct tcp_sock *tp, u32 cnt)
{
	if (cnt > 0 && 	tp->ca_state == TCP_CA_Open) {
		struct bictcp *ca = tcp_ca(tp);
		cnt -= ca->delayed_ack >> ACK_RATIO_SHIFT;
		ca->delayed_ack += cnt;
	}
}


static struct tcp_congestion_ops bictcp = {
	.init		= bictcp_init,
	.ssthresh	= bictcp_recalc_ssthresh,
	.cong_avoid	= bictcp_cong_avoid,
	.set_state	= bictcp_state,
	.undo_cwnd	= bictcp_undo_cwnd,
	.min_cwnd	= bictcp_min_cwnd,
	.pkts_acked     = bictcp_acked,
	.owner		= THIS_MODULE,
	.name		= "bic",
};

static int __init bictcp_register(void)
{
	BUG_ON(sizeof(struct bictcp) > TCP_CA_PRIV_SIZE);
	return tcp_register_congestion_control(&bictcp);
}

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

module_init(bictcp_register);
module_exit(bictcp_unregister);

MODULE_AUTHOR("Stephen Hemminger");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("BIC TCP");
Commit	Line	Data
83803034 SH	1	/*
	2	* Binary Increase Congestion control for TCP
	3	*
	4	* This is from the implementation of BICTCP in
	5	* Lison-Xu, Kahaled Harfoush, and Injong Rhee.
	6	* "Binary Increase Congestion Control for Fast, Long Distance
	7	* Networks" in InfoComm 2004
	8	* Available from:
	9	* http://www.csc.ncsu.edu/faculty/rhee/export/bitcp.pdf
	10	*
	11	* Unless BIC is enabled and congestion window is large
	12	* this behaves the same as the original Reno.
	13	*/
	14
	15	#include <linux/config.h>
	16	#include <linux/mm.h>
	17	#include <linux/module.h>
	18	#include <net/tcp.h>
	19
	20
	21	#define BICTCP_BETA_SCALE 1024 /* Scale factor beta calculation
	22	* max_cwnd = snd_cwnd * beta
	23	*/
	24	#define BICTCP_B 4 /*
	25	* In binary search,
	26	* go to point (max+min)/N
	27	*/
	28
	29	static int fast_convergence = 1;
	30	static int max_increment = 32;
	31	static int low_window = 14;
	32	static int beta = 819; /* = 819/1024 (BICTCP_BETA_SCALE) */
	33	static int low_utilization_threshold = 153;
	34	static int low_utilization_period = 2;
	35	static int initial_ssthresh = 100;
	36	static int smooth_part = 20;
	37
	38	module_param(fast_convergence, int, 0644);
	39	MODULE_PARM_DESC(fast_convergence, "turn on/off fast convergence");
	40	module_param(max_increment, int, 0644);
	41	MODULE_PARM_DESC(max_increment, "Limit on increment allowed during binary search");
	42	module_param(low_window, int, 0644);
	43	MODULE_PARM_DESC(low_window, "lower bound on congestion window (for TCP friendliness)");
	44	module_param(beta, int, 0644);
	45	MODULE_PARM_DESC(beta, "beta for multiplicative increase");
	46	module_param(low_utilization_threshold, int, 0644);
	47	MODULE_PARM_DESC(low_utilization_threshold, "percent (scaled by 1024) for low utilization mode");
	48	module_param(low_utilization_period, int, 0644);
	49	MODULE_PARM_DESC(low_utilization_period, "if average delay exceeds then goto to low utilization mode (seconds)");
	50	module_param(initial_ssthresh, int, 0644);
	51	MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold");
	52	module_param(smooth_part, int, 0644);
	53	MODULE_PARM_DESC(smooth_part, "log(B/(B*Smin))/log(B/(B-1))+B, # of RTT from Wmax-B to Wmax");
	54
	55
	56	/* BIC TCP Parameters */
	57	struct bictcp {
	58	u32 cnt; /* increase cwnd by 1 after ACKs */
	59	u32 last_max_cwnd; /* last maximum snd_cwnd */
	60	u32 loss_cwnd; /* congestion window at last loss */
	61	u32 last_cwnd; /* the last snd_cwnd */
	62	u32 last_time; /* time when updated last_cwnd */
	63	u32 delay_min; /* min delay */
	64	u32 delay_max; /* max delay */
65	u32 last_delay;
66	u8 low_utilization;/* 0: high; 1: low */
67	u32 low_utilization_start; /* starting time of low utilization detection*/
68	u32 epoch_start; /* beginning of an epoch */
69	#define ACK_RATIO_SHIFT 4
70	u32 delayed_ack; /* estimate the ratio of Packets/ACKs << 4 */
71	};
72
73	static inline void bictcp_reset(struct bictcp *ca)
74	{
75	ca->cnt = 0;
76	ca->last_max_cwnd = 0;
77	ca->loss_cwnd = 0;
78	ca->last_cwnd = 0;
79	ca->last_time = 0;
80	ca->delay_min = 0;
81	ca->delay_max = 0;
82	ca->last_delay = 0;
83	ca->low_utilization = 0;
84	ca->low_utilization_start = 0;
85	ca->epoch_start = 0;
86	ca->delayed_ack = 2 << ACK_RATIO_SHIFT;
87	}
88
89	static void bictcp_init(struct tcp_sock *tp)
90	{
91	bictcp_reset(tcp_ca(tp));
92	if (initial_ssthresh)
93	tp->snd_ssthresh = initial_ssthresh;
94	}
95
96	/*
97	* Compute congestion window to use.
98	*/
99	static inline void bictcp_update(struct bictcp *ca, u32 cwnd)
100	{
101	if (ca->last_cwnd == cwnd &&
102	(s32)(tcp_time_stamp - ca->last_time) <= HZ / 32)
103	return;
104
105	ca->last_cwnd = cwnd;
106	ca->last_time = tcp_time_stamp;
107
108	if (ca->epoch_start == 0) /* record the beginning of an epoch */
109	ca->epoch_start = tcp_time_stamp;
110
111	/* start off normal */
112	if (cwnd <= low_window) {
113	ca->cnt = cwnd;
114	return;
115	}
116
117	/* binary increase */
118	if (cwnd < ca->last_max_cwnd) {
119	__u32 dist = (ca->last_max_cwnd - cwnd)
120	/ BICTCP_B;
121
122	if (dist > max_increment)
123	/* linear increase */
124	ca->cnt = cwnd / max_increment;
125	else if (dist <= 1U)
126	/* binary search increase */
127	ca->cnt = (cwnd * smooth_part) / BICTCP_B;
128	else
129	/* binary search increase */
130	ca->cnt = cwnd / dist;
131	} else {
132	/* slow start AMD linear increase */
133	if (cwnd < ca->last_max_cwnd + BICTCP_B)
134	/* slow start */
135	ca->cnt = (cwnd * smooth_part) / BICTCP_B;
136	else if (cwnd < ca->last_max_cwnd + max_increment*(BICTCP_B-1))
137	/* slow start */
138	ca->cnt = (cwnd * (BICTCP_B-1))
139	/ cwnd-ca->last_max_cwnd;
140	else
141	/* linear increase */
142	ca->cnt = cwnd / max_increment;
143	}
144
145	/* if in slow start or link utilization is very low */
146	if ( ca->loss_cwnd == 0 \|\|
147	(cwnd > ca->loss_cwnd && ca->low_utilization)) {
148	if (ca->cnt > 20) /* increase cwnd 5% per RTT */
149	ca->cnt = 20;
150	}
151
152	ca->cnt = (ca->cnt << ACK_RATIO_SHIFT) / ca->delayed_ack;
153	if (ca->cnt == 0) /* cannot be zero */
154	ca->cnt = 1;
155	}
156
157
158	/* Detect low utilization in congestion avoidance */
159	static inline void bictcp_low_utilization(struct tcp_sock *tp, int flag)
160	{
161	struct bictcp *ca = tcp_ca(tp);
162	u32 dist, delay;
163
164	/* No time stamp */
165	if (!(tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) \|\|
166	/* Discard delay samples right after fast recovery */
167	tcp_time_stamp < ca->epoch_start + HZ \|\|
168	/* this delay samples may not be accurate */
169	flag == 0) {
170	ca->last_delay = 0;
171	goto notlow;
172	}
173
174	delay = ca->last_delay<<3; /* use the same scale as tp->srtt*/
175	ca->last_delay = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
176	if (delay == 0) /* no previous delay sample */
177	goto notlow;
178
179	/* first time call or link delay decreases */
180	if (ca->delay_min == 0 \|\| ca->delay_min > delay) {
181	ca->delay_min = ca->delay_max = delay;
182	goto notlow;
183	}
184
185	if (ca->delay_max < delay)
186	ca->delay_max = delay;
187
188	/* utilization is low, if avg delay < dist*threshold
189	for checking_period time */
190	dist = ca->delay_max - ca->delay_min;
191	if (dist <= ca->delay_min>>6 \|\|
192	tp->srtt - ca->delay_min >= (dist*low_utilization_threshold)>>10)
193	goto notlow;
194
195	if (ca->low_utilization_start == 0) {
196	ca->low_utilization = 0;
197	ca->low_utilization_start = tcp_time_stamp;
198	} else if ((s32)(tcp_time_stamp - ca->low_utilization_start)
199	> low_utilization_period*HZ) {
200	ca->low_utilization = 1;
201	}
202
203	return;
204
205	notlow:
206	ca->low_utilization = 0;
207	ca->low_utilization_start = 0;
208
209	}
210
211	static void bictcp_cong_avoid(struct tcp_sock *tp, u32 ack,
212	u32 seq_rtt, u32 in_flight, int data_acked)
213	{
214	struct bictcp *ca = tcp_ca(tp);
215
216	bictcp_low_utilization(tp, data_acked);
217
218	if (in_flight < tp->snd_cwnd)
219	return;
220
221	if (tp->snd_cwnd <= tp->snd_ssthresh) {
222	/* In "safe" area, increase. */
223	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
224	tp->snd_cwnd++;
225	} else {
226	bictcp_update(ca, tp->snd_cwnd);
227
228	/* In dangerous area, increase slowly.
229	* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
230	*/
231	if (tp->snd_cwnd_cnt >= ca->cnt) {
232	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
233	tp->snd_cwnd++;
234	tp->snd_cwnd_cnt = 0;
235	} else
236	tp->snd_cwnd_cnt++;
237	}
238
239	}
240
241	/*
242	* behave like Reno until low_window is reached,
243	* then increase congestion window slowly
244	*/
245	static u32 bictcp_recalc_ssthresh(struct tcp_sock *tp)
246	{
247	struct bictcp *ca = tcp_ca(tp);
248
249	ca->epoch_start = 0; /* end of epoch */
250
251	/* in case of wrong delay_max*/
252	if (ca->delay_min > 0 && ca->delay_max > ca->delay_min)
253	ca->delay_max = ca->delay_min
254	+ ((ca->delay_max - ca->delay_min)* 90) / 100;
255
256	/* Wmax and fast convergence */
257	if (tp->snd_cwnd < ca->last_max_cwnd && fast_convergence)
258	ca->last_max_cwnd = (tp->snd_cwnd * (BICTCP_BETA_SCALE + beta))
259	/ (2 * BICTCP_BETA_SCALE);
260	else
261	ca->last_max_cwnd = tp->snd_cwnd;
262
263	ca->loss_cwnd = tp->snd_cwnd;
264
265
266	if (tp->snd_cwnd <= low_window)
267	return max(tp->snd_cwnd >> 1U, 2U);
268	else
269	return max((tp->snd_cwnd * beta) / BICTCP_BETA_SCALE, 2U);
270	}
271
272	static u32 bictcp_undo_cwnd(struct tcp_sock *tp)
273	{
274	struct bictcp *ca = tcp_ca(tp);
275
276	return max(tp->snd_cwnd, ca->last_max_cwnd);
277	}
278
279	static u32 bictcp_min_cwnd(struct tcp_sock *tp)
280	{
281	return tp->snd_ssthresh;
282	}
283
284	static void bictcp_state(struct tcp_sock *tp, u8 new_state)
285	{
286	if (new_state == TCP_CA_Loss)
287	bictcp_reset(tcp_ca(tp));
288	}
289
290	/* Track delayed acknowledgement ratio using sliding window
291	* ratio = (15*ratio + sample) / 16
292	*/
293	static void bictcp_acked(struct tcp_sock *tp, u32 cnt)
294	{
295	if (cnt > 0 && tp->ca_state == TCP_CA_Open) {
296	struct bictcp *ca = tcp_ca(tp);
297	cnt -= ca->delayed_ack >> ACK_RATIO_SHIFT;
298	ca->delayed_ack += cnt;
299	}
300	}
301
302
303	static struct tcp_congestion_ops bictcp = {
304	.init = bictcp_init,
305	.ssthresh = bictcp_recalc_ssthresh,
306	.cong_avoid = bictcp_cong_avoid,
307	.set_state = bictcp_state,
308	.undo_cwnd = bictcp_undo_cwnd,
309	.min_cwnd = bictcp_min_cwnd,
310	.pkts_acked = bictcp_acked,
311	.owner = THIS_MODULE,
312	.name = "bic",
313	};
314
315	static int __init bictcp_register(void)
316	{
317	BUG_ON(sizeof(struct bictcp) > TCP_CA_PRIV_SIZE);
318	return tcp_register_congestion_control(&bictcp);
319	}
320
321	static void __exit bictcp_unregister(void)
322	{
323	tcp_unregister_congestion_control(&bictcp);
324	}
325
326	module_init(bictcp_register);
327	module_exit(bictcp_unregister);
328
329	MODULE_AUTHOR("Stephen Hemminger");
330	MODULE_LICENSE("GPL");
331	MODULE_DESCRIPTION("BIC TCP");