[deliverable/linux.git] / net / ipv4 / tcp_htcp.c

/*
 * H-TCP congestion control. The algorithm is detailed in:
 * R.N.Shorten, D.J.Leith:
 *   "H-TCP: TCP for high-speed and long-distance networks"
 *   Proc. PFLDnet, Argonne, 2004.
 * http://www.hamilton.ie/net/htcp3.pdf
 */

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

#define ALPHA_BASE	(1<<7)  /* 1.0 with shift << 7 */
#define BETA_MIN	(1<<6)  /* 0.5 with shift << 7 */
#define BETA_MAX	102	/* 0.8 with shift << 7 */

static int use_rtt_scaling = 1;
module_param(use_rtt_scaling, int, 0644);
MODULE_PARM_DESC(use_rtt_scaling, "turn on/off RTT scaling");

static int use_bandwidth_switch = 1;
module_param(use_bandwidth_switch, int, 0644);
MODULE_PARM_DESC(use_bandwidth_switch, "turn on/off bandwidth switcher");

struct htcp {
	u16	alpha;		/* Fixed point arith, << 7 */
	u8	beta;           /* Fixed point arith, << 7 */
	u8	modeswitch;     /* Delay modeswitch until we had at least one congestion event */
	u8	ccount;		/* Number of RTTs since last congestion event */
	u8	undo_ccount;
	u16	packetcount;
	u32	minRTT;
	u32	maxRTT;
	u32	snd_cwnd_cnt2;

	u32	undo_maxRTT;
	u32	undo_old_maxB;

	/* Bandwidth estimation */
	u32	minB;
	u32	maxB;
	u32	old_maxB;
	u32	Bi;
	u32	lasttime;
};

static inline void htcp_reset(struct htcp *ca)
{
	ca->undo_ccount = ca->ccount;
	ca->undo_maxRTT = ca->maxRTT;
	ca->undo_old_maxB = ca->old_maxB;

	ca->ccount = 0;
	ca->snd_cwnd_cnt2 = 0;
}

static u32 htcp_cwnd_undo(struct tcp_sock *tp)
{
	struct htcp *ca = tcp_ca(tp);
	ca->ccount = ca->undo_ccount;
	ca->maxRTT = ca->undo_maxRTT;
	ca->old_maxB = ca->undo_old_maxB;
	return max(tp->snd_cwnd, (tp->snd_ssthresh<<7)/ca->beta);
}

static inline void measure_rtt(struct tcp_sock *tp)
{
	struct htcp *ca = tcp_ca(tp);
	u32 srtt = tp->srtt>>3;

	/* keep track of minimum RTT seen so far, minRTT is zero at first */
	if (ca->minRTT > srtt || !ca->minRTT)
		ca->minRTT = srtt;

	/* max RTT */
	if (tp->ca_state == TCP_CA_Open && tp->snd_ssthresh < 0xFFFF && ca->ccount > 3) {
		if (ca->maxRTT < ca->minRTT)
			ca->maxRTT = ca->minRTT;
		if (ca->maxRTT < srtt && srtt <= ca->maxRTT+HZ/50)
			ca->maxRTT = srtt;
	}
}

static void measure_achieved_throughput(struct tcp_sock *tp, u32 pkts_acked)
{
	struct htcp *ca = tcp_ca(tp);
	u32 now = tcp_time_stamp;

	/* achieved throughput calculations */
	if (tp->ca_state != TCP_CA_Open && tp->ca_state != TCP_CA_Disorder) {
		ca->packetcount = 0;
		ca->lasttime = now;
		return;
	}

	ca->packetcount += pkts_acked;

	if (ca->packetcount >= tp->snd_cwnd - (ca->alpha>>7? : 1)
			&& now - ca->lasttime >= ca->minRTT
			&& ca->minRTT > 0) {
		__u32 cur_Bi = ca->packetcount*HZ/(now - ca->lasttime);
		if (ca->ccount <= 3) {
			/* just after backoff */
			ca->minB = ca->maxB = ca->Bi = cur_Bi;
		} else {
			ca->Bi = (3*ca->Bi + cur_Bi)/4;
			if (ca->Bi > ca->maxB)
				ca->maxB = ca->Bi;
			if (ca->minB > ca->maxB)
				ca->minB = ca->maxB;
		}
		ca->packetcount = 0;
		ca->lasttime = now;
	}
}

static inline void htcp_beta_update(struct htcp *ca, u32 minRTT, u32 maxRTT)
{
	if (use_bandwidth_switch) {
		u32 maxB = ca->maxB;
		u32 old_maxB = ca->old_maxB;
		ca->old_maxB = ca->maxB;

		if (!between(5*maxB, 4*old_maxB, 6*old_maxB)) {
			ca->beta = BETA_MIN;
			ca->modeswitch = 0;
			return;
		}
	}

	if (ca->modeswitch && minRTT > max(HZ/100, 1) && maxRTT) {
		ca->beta = (minRTT<<7)/maxRTT;
		if (ca->beta < BETA_MIN)
			ca->beta = BETA_MIN;
		else if (ca->beta > BETA_MAX)
			ca->beta = BETA_MAX;
	} else {
		ca->beta = BETA_MIN;
		ca->modeswitch = 1;
	}
}

static inline void htcp_alpha_update(struct htcp *ca)
{
	u32 minRTT = ca->minRTT;
	u32 factor = 1;
	u32 diff = ca->ccount * minRTT; /* time since last backoff */

	if (diff > HZ) {
		diff -= HZ;
		factor = 1+ ( 10*diff + ((diff/2)*(diff/2)/HZ) )/HZ;
	}

	if (use_rtt_scaling && minRTT) {
		u32 scale = (HZ<<3)/(10*minRTT);
		scale = min(max(scale, 1U<<2), 10U<<3); /* clamping ratio to interval [0.5,10]<<3 */
		factor = (factor<<3)/scale;
		if (!factor)
			factor = 1;
	}

	ca->alpha = 2*factor*((1<<7)-ca->beta);
	if (!ca->alpha)
		ca->alpha = ALPHA_BASE;
}

/* After we have the rtt data to calculate beta, we'd still prefer to wait one
 * rtt before we adjust our beta to ensure we are working from a consistent
 * data.
 *
 * This function should be called when we hit a congestion event since only at
 * that point do we really have a real sense of maxRTT (the queues en route
 * were getting just too full now).
 */
static void htcp_param_update(struct tcp_sock *tp)
{
	struct htcp *ca = tcp_ca(tp);
	u32 minRTT = ca->minRTT;
	u32 maxRTT = ca->maxRTT;

	htcp_beta_update(ca, minRTT, maxRTT);
	htcp_alpha_update(ca);

	/* add slowly fading memory for maxRTT to accommodate routing changes etc */
	if (minRTT > 0 && maxRTT > minRTT)
		ca->maxRTT = minRTT + ((maxRTT-minRTT)*95)/100;
}

static u32 htcp_recalc_ssthresh(struct tcp_sock *tp)
{
	struct htcp *ca = tcp_ca(tp);
	htcp_param_update(tp);
	return max((tp->snd_cwnd * ca->beta) >> 7, 2U);
}

static void htcp_cong_avoid(struct tcp_sock *tp, u32 ack, u32 rtt,
			    u32 in_flight, int data_acked)
{
	struct htcp *ca = tcp_ca(tp);

	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 {
		measure_rtt(tp);

		/* keep track of number of round-trip times since last backoff event */
		if (ca->snd_cwnd_cnt2++ > tp->snd_cwnd) {
			ca->ccount++;
			ca->snd_cwnd_cnt2 = 0;
			htcp_alpha_update(ca);
		}

                /* In dangerous area, increase slowly.
		 * In theory this is tp->snd_cwnd += alpha / tp->snd_cwnd
		 */
		if ((tp->snd_cwnd_cnt++ * ca->alpha)>>7 >= tp->snd_cwnd) {
			if (tp->snd_cwnd < tp->snd_cwnd_clamp)
				tp->snd_cwnd++;
			tp->snd_cwnd_cnt = 0;
			ca->ccount++;
		}
	}
}

/* Lower bound on congestion window. */
static u32 htcp_min_cwnd(struct tcp_sock *tp)
{
	return tp->snd_ssthresh;
}


static void htcp_init(struct tcp_sock *tp)
{
	struct htcp *ca = tcp_ca(tp);

	memset(ca, 0, sizeof(struct htcp));
	ca->alpha = ALPHA_BASE;
	ca->beta = BETA_MIN;
}

static void htcp_state(struct tcp_sock *tp, u8 new_state)
{
	switch (new_state) {
	case TCP_CA_CWR:
	case TCP_CA_Recovery:
	case TCP_CA_Loss:
		htcp_reset(tcp_ca(tp));
		break;
	}
}

static struct tcp_congestion_ops htcp = {
	.init		= htcp_init,
	.ssthresh	= htcp_recalc_ssthresh,
	.min_cwnd	= htcp_min_cwnd,
	.cong_avoid	= htcp_cong_avoid,
	.set_state	= htcp_state,
	.undo_cwnd	= htcp_cwnd_undo,
	.pkts_acked	= measure_achieved_throughput,
	.owner		= THIS_MODULE,
	.name		= "htcp",
};

static int __init htcp_register(void)
{
	BUG_ON(sizeof(struct htcp) > TCP_CA_PRIV_SIZE);
	BUILD_BUG_ON(BETA_MIN >= BETA_MAX);
	if (!use_bandwidth_switch)
		htcp.pkts_acked = NULL;
	return tcp_register_congestion_control(&htcp);
}

static void __exit htcp_unregister(void)
{
	tcp_unregister_congestion_control(&htcp);
}

module_init(htcp_register);
module_exit(htcp_unregister);

MODULE_AUTHOR("Baruch Even");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("H-TCP");
Commit	Line	Data
a7868ea6 BE	1	/*
	2	* H-TCP congestion control. The algorithm is detailed in:
	3	* R.N.Shorten, D.J.Leith:
	4	* "H-TCP: TCP for high-speed and long-distance networks"
	5	* Proc. PFLDnet, Argonne, 2004.
	6	* http://www.hamilton.ie/net/htcp3.pdf
	7	*/
	8
	9	#include <linux/config.h>
	10	#include <linux/mm.h>
	11	#include <linux/module.h>
	12	#include <net/tcp.h>
	13
	14	#define ALPHA_BASE (1<<7) /* 1.0 with shift << 7 */
	15	#define BETA_MIN (1<<6) /* 0.5 with shift << 7 */
	16	#define BETA_MAX 102 /* 0.8 with shift << 7 */
	17
	18	static int use_rtt_scaling = 1;
	19	module_param(use_rtt_scaling, int, 0644);
	20	MODULE_PARM_DESC(use_rtt_scaling, "turn on/off RTT scaling");
	21
	22	static int use_bandwidth_switch = 1;
	23	module_param(use_bandwidth_switch, int, 0644);
	24	MODULE_PARM_DESC(use_bandwidth_switch, "turn on/off bandwidth switcher");
	25
	26	struct htcp {
	27	u16 alpha; /* Fixed point arith, << 7 */
	28	u8 beta; /* Fixed point arith, << 7 */
	29	u8 modeswitch; /* Delay modeswitch until we had at least one congestion event */
	30	u8 ccount; /* Number of RTTs since last congestion event */
	31	u8 undo_ccount;
	32	u16 packetcount;
	33	u32 minRTT;
	34	u32 maxRTT;
	35	u32 snd_cwnd_cnt2;
	36
	37	u32 undo_maxRTT;
	38	u32 undo_old_maxB;
	39
	40	/* Bandwidth estimation */
	41	u32 minB;
	42	u32 maxB;
	43	u32 old_maxB;
	44	u32 Bi;
	45	u32 lasttime;
	46	};
	47
	48	static inline void htcp_reset(struct htcp *ca)
	49	{
	50	ca->undo_ccount = ca->ccount;
	51	ca->undo_maxRTT = ca->maxRTT;
	52	ca->undo_old_maxB = ca->old_maxB;
	53
	54	ca->ccount = 0;
	55	ca->snd_cwnd_cnt2 = 0;
	56	}
	57
	58	static u32 htcp_cwnd_undo(struct tcp_sock *tp)
	59	{
	60	struct htcp *ca = tcp_ca(tp);
	61	ca->ccount = ca->undo_ccount;
	62	ca->maxRTT = ca->undo_maxRTT;
	63	ca->old_maxB = ca->undo_old_maxB;
	64	return max(tp->snd_cwnd, (tp->snd_ssthresh<<7)/ca->beta);
65	}
66
67	static inline void measure_rtt(struct tcp_sock *tp)
68	{
69	struct htcp *ca = tcp_ca(tp);
70	u32 srtt = tp->srtt>>3;
71
72	/* keep track of minimum RTT seen so far, minRTT is zero at first */
73	if (ca->minRTT > srtt \|\| !ca->minRTT)
74	ca->minRTT = srtt;
75
76	/* max RTT */
77	if (tp->ca_state == TCP_CA_Open && tp->snd_ssthresh < 0xFFFF && ca->ccount > 3) {
78	if (ca->maxRTT < ca->minRTT)
79	ca->maxRTT = ca->minRTT;
80	if (ca->maxRTT < srtt && srtt <= ca->maxRTT+HZ/50)
81	ca->maxRTT = srtt;
82	}
83	}
84
85	static void measure_achieved_throughput(struct tcp_sock *tp, u32 pkts_acked)
86	{
87	struct htcp *ca = tcp_ca(tp);
88	u32 now = tcp_time_stamp;
89
90	/* achieved throughput calculations */
91	if (tp->ca_state != TCP_CA_Open && tp->ca_state != TCP_CA_Disorder) {
92	ca->packetcount = 0;
93	ca->lasttime = now;
94	return;
95	}
96
97	ca->packetcount += pkts_acked;
98
99	if (ca->packetcount >= tp->snd_cwnd - (ca->alpha>>7? : 1)
100	&& now - ca->lasttime >= ca->minRTT
101	&& ca->minRTT > 0) {
102	__u32 cur_Bi = ca->packetcount*HZ/(now - ca->lasttime);
103	if (ca->ccount <= 3) {
104	/* just after backoff */
105	ca->minB = ca->maxB = ca->Bi = cur_Bi;
106	} else {
107	ca->Bi = (3*ca->Bi + cur_Bi)/4;
108	if (ca->Bi > ca->maxB)
109	ca->maxB = ca->Bi;
110	if (ca->minB > ca->maxB)
111	ca->minB = ca->maxB;
112	}
113	ca->packetcount = 0;
114	ca->lasttime = now;
115	}
116	}
117
118	static inline void htcp_beta_update(struct htcp *ca, u32 minRTT, u32 maxRTT)
119	{
120	if (use_bandwidth_switch) {
121	u32 maxB = ca->maxB;
122	u32 old_maxB = ca->old_maxB;
123	ca->old_maxB = ca->maxB;
124
125	if (!between(5maxB, 4old_maxB, 6*old_maxB)) {
126	ca->beta = BETA_MIN;
127	ca->modeswitch = 0;
128	return;
129	}
130	}
131
132	if (ca->modeswitch && minRTT > max(HZ/100, 1) && maxRTT) {
133	ca->beta = (minRTT<<7)/maxRTT;
134	if (ca->beta < BETA_MIN)
135	ca->beta = BETA_MIN;
136	else if (ca->beta > BETA_MAX)
137	ca->beta = BETA_MAX;
138	} else {
139	ca->beta = BETA_MIN;
140	ca->modeswitch = 1;
141	}
142	}
143
144	static inline void htcp_alpha_update(struct htcp *ca)
145	{
146	u32 minRTT = ca->minRTT;
147	u32 factor = 1;
148	u32 diff = ca->ccount * minRTT; /* time since last backoff */
149
150	if (diff > HZ) {
151	diff -= HZ;
152	factor = 1+ ( 10diff + ((diff/2)(diff/2)/HZ) )/HZ;
153	}
154
155	if (use_rtt_scaling && minRTT) {
156	u32 scale = (HZ<<3)/(10*minRTT);
157	scale = min(max(scale, 1U<<2), 10U<<3); /* clamping ratio to interval [0.5,10]<<3 */
158	factor = (factor<<3)/scale;
159	if (!factor)
160	factor = 1;
161	}
162
163	ca->alpha = 2factor((1<<7)-ca->beta);
164	if (!ca->alpha)
165	ca->alpha = ALPHA_BASE;
166	}
167
168	/* After we have the rtt data to calculate beta, we'd still prefer to wait one
169	* rtt before we adjust our beta to ensure we are working from a consistent
170	* data.
171	*
172	* This function should be called when we hit a congestion event since only at
173	* that point do we really have a real sense of maxRTT (the queues en route
174	* were getting just too full now).
175	*/
176	static void htcp_param_update(struct tcp_sock *tp)
177	{
178	struct htcp *ca = tcp_ca(tp);
179	u32 minRTT = ca->minRTT;
180	u32 maxRTT = ca->maxRTT;
181
182	htcp_beta_update(ca, minRTT, maxRTT);
183	htcp_alpha_update(ca);
184
185	/* add slowly fading memory for maxRTT to accommodate routing changes etc */
186	if (minRTT > 0 && maxRTT > minRTT)
187	ca->maxRTT = minRTT + ((maxRTT-minRTT)*95)/100;
188	}
189
190	static u32 htcp_recalc_ssthresh(struct tcp_sock *tp)
191	{
192	struct htcp *ca = tcp_ca(tp);
193	htcp_param_update(tp);
194	return max((tp->snd_cwnd * ca->beta) >> 7, 2U);
195	}
196
197	static void htcp_cong_avoid(struct tcp_sock *tp, u32 ack, u32 rtt,
198	u32 in_flight, int data_acked)
199	{
200	struct htcp *ca = tcp_ca(tp);
201
202	if (in_flight < tp->snd_cwnd)
203	return;
204
205	if (tp->snd_cwnd <= tp->snd_ssthresh) {
206	/* In "safe" area, increase. */
207	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
208	tp->snd_cwnd++;
209	} else {
210	measure_rtt(tp);
211
212	/* keep track of number of round-trip times since last backoff event */
213	if (ca->snd_cwnd_cnt2++ > tp->snd_cwnd) {
214	ca->ccount++;
215	ca->snd_cwnd_cnt2 = 0;
216	htcp_alpha_update(ca);
217	}
218
219	/* In dangerous area, increase slowly.
220	* In theory this is tp->snd_cwnd += alpha / tp->snd_cwnd
221	*/
222	if ((tp->snd_cwnd_cnt++ * ca->alpha)>>7 >= tp->snd_cwnd) {
223	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
224	tp->snd_cwnd++;
225	tp->snd_cwnd_cnt = 0;
226	ca->ccount++;
227	}
228	}
229	}
230
231	/* Lower bound on congestion window. */
232	static u32 htcp_min_cwnd(struct tcp_sock *tp)
233	{
234	return tp->snd_ssthresh;
235	}
236
237
238	static void htcp_init(struct tcp_sock *tp)
239	{
240	struct htcp *ca = tcp_ca(tp);
241
242	memset(ca, 0, sizeof(struct htcp));
243	ca->alpha = ALPHA_BASE;
244	ca->beta = BETA_MIN;
245	}
246
247	static void htcp_state(struct tcp_sock *tp, u8 new_state)
248	{
249	switch (new_state) {
250	case TCP_CA_CWR:
251	case TCP_CA_Recovery:
252	case TCP_CA_Loss:
253	htcp_reset(tcp_ca(tp));
254	break;
255	}
256	}
257
258	static struct tcp_congestion_ops htcp = {
259	.init = htcp_init,
260	.ssthresh = htcp_recalc_ssthresh,
261	.min_cwnd = htcp_min_cwnd,
262	.cong_avoid = htcp_cong_avoid,
263	.set_state = htcp_state,
264	.undo_cwnd = htcp_cwnd_undo,
265	.pkts_acked = measure_achieved_throughput,
266	.owner = THIS_MODULE,
267	.name = "htcp",
268	};
269
270	static int __init htcp_register(void)
271	{
272	BUG_ON(sizeof(struct htcp) > TCP_CA_PRIV_SIZE);
273	BUILD_BUG_ON(BETA_MIN >= BETA_MAX);
274	if (!use_bandwidth_switch)
275	htcp.pkts_acked = NULL;
276	return tcp_register_congestion_control(&htcp);
277	}
278
279	static void __exit htcp_unregister(void)
280	{
281	tcp_unregister_congestion_control(&htcp);
282	}
283
284	module_init(htcp_register);
285	module_exit(htcp_unregister);
286
287	MODULE_AUTHOR("Baruch Even");
288	MODULE_LICENSE("GPL");
289	MODULE_DESCRIPTION("H-TCP");