[net-next-2.6.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/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 {
	u32	alpha;		/* Fixed point arith, << 7 */
	u8	beta;           /* Fixed point arith, << 7 */
	u8	modeswitch;     /* Delay modeswitch until we had at least one congestion event */
	u16	pkts_acked;
	u32	packetcount;
	u32	minRTT;
	u32	maxRTT;
	u32	last_cong;	/* Time since last congestion event end */
	u32	undo_last_cong;

	u32	undo_maxRTT;
	u32	undo_old_maxB;

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

static inline u32 htcp_cong_time(struct htcp *ca)
{
	return jiffies - ca->last_cong;
}

static inline u32 htcp_ccount(struct htcp *ca)
{
	return htcp_cong_time(ca)/ca->minRTT;
}

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

	ca->last_cong = jiffies;
}

static u32 htcp_cwnd_undo(struct sock *sk)
{
	const struct tcp_sock *tp = tcp_sk(sk);
	struct htcp *ca = inet_csk_ca(sk);
	ca->last_cong = ca->undo_last_cong;
	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 sock *sk)
{
	const struct inet_connection_sock *icsk = inet_csk(sk);
	const struct tcp_sock *tp = tcp_sk(sk);
	struct htcp *ca = inet_csk_ca(sk);
	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 (icsk->icsk_ca_state == TCP_CA_Open && tp->snd_ssthresh < 0xFFFF && htcp_ccount(ca) > 3) {
		if (ca->maxRTT < ca->minRTT)
			ca->maxRTT = ca->minRTT;
		if (ca->maxRTT < srtt && srtt <= ca->maxRTT+msecs_to_jiffies(20))
			ca->maxRTT = srtt;
	}
}

static void measure_achieved_throughput(struct sock *sk, u32 pkts_acked)
{
	const struct inet_connection_sock *icsk = inet_csk(sk);
	const struct tcp_sock *tp = tcp_sk(sk);
	struct htcp *ca = inet_csk_ca(sk);
	u32 now = tcp_time_stamp;

	if (icsk->icsk_ca_state == TCP_CA_Open)
		ca->pkts_acked = pkts_acked;

	if (!use_bandwidth_switch)
		return;

	/* achieved throughput calculations */
	if (icsk->icsk_ca_state != TCP_CA_Open &&
	    icsk->icsk_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 (htcp_ccount(ca) <= 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 > msecs_to_jiffies(10) && 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 = htcp_cong_time(ca);

	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 sock *sk)
{
	struct htcp *ca = inet_csk_ca(sk);
	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 sock *sk)
{
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct htcp *ca = inet_csk_ca(sk);
	htcp_param_update(sk);
	return max((tp->snd_cwnd * ca->beta) >> 7, 2U);
}

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

	if (!tcp_is_cwnd_limited(sk, in_flight))
		return;

	if (tp->snd_cwnd <= tp->snd_ssthresh)
		tcp_slow_start(tp);
	else {

		measure_rtt(sk);

		/* 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;
			htcp_alpha_update(ca);
		} else
			tp->snd_cwnd_cnt += ca->pkts_acked;

		ca->pkts_acked = 1;
	}
}

static void htcp_init(struct sock *sk)
{
	struct htcp *ca = inet_csk_ca(sk);

	memset(ca, 0, sizeof(struct htcp));
	ca->alpha = ALPHA_BASE;
	ca->beta = BETA_MIN;
	ca->pkts_acked = 1;
	ca->last_cong = jiffies;
}

static void htcp_state(struct sock *sk, u8 new_state)
{
	switch (new_state) {
	case TCP_CA_Open:
		{
			struct htcp *ca = inet_csk_ca(sk);
			ca->last_cong = jiffies;
		}
		break;
	case TCP_CA_CWR:
	case TCP_CA_Recovery:
	case TCP_CA_Loss:
		htcp_reset(inet_csk_ca(sk));
		break;
	}
}

static struct tcp_congestion_ops htcp = {
	.init		= htcp_init,
	.ssthresh	= htcp_recalc_ssthresh,
	.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)
{
	BUILD_BUG_ON(sizeof(struct htcp) > ICSK_CA_PRIV_SIZE);
	BUILD_BUG_ON(BETA_MIN >= BETA_MAX);
	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
a7868ea6 BE	9	#include <linux/mm.h>
	10	#include <linux/module.h>
	11	#include <net/tcp.h>
	12
	13	#define ALPHA_BASE (1<<7) /* 1.0 with shift << 7 */
	14	#define BETA_MIN (1<<6) /* 0.5 with shift << 7 */
	15	#define BETA_MAX 102 /* 0.8 with shift << 7 */
	16
	17	static int use_rtt_scaling = 1;
	18	module_param(use_rtt_scaling, int, 0644);
	19	MODULE_PARM_DESC(use_rtt_scaling, "turn on/off RTT scaling");
	20
	21	static int use_bandwidth_switch = 1;
	22	module_param(use_bandwidth_switch, int, 0644);
	23	MODULE_PARM_DESC(use_bandwidth_switch, "turn on/off bandwidth switcher");
	24
	25	struct htcp {
2a272f98	26	u32 alpha; /* Fixed point arith, << 7 */
a7868ea6 BE	27	u8 beta; /* Fixed point arith, << 7 */
a7868ea6 BE	28	u8 modeswitch; /* Delay modeswitch until we had at least one congestion event */
0bc6d90b BE	29	u16 pkts_acked;
0bc6d90b BE	30	u32 packetcount;
a7868ea6 BE	31	u32 minRTT;
a7868ea6 BE	32	u32 maxRTT;
2404043a DM	33	u32 last_cong; /* Time since last congestion event end */
2404043a DM	34	u32 undo_last_cong;
a7868ea6 BE	35
	36	u32 undo_maxRTT;
	37	u32 undo_old_maxB;
	38
	39	/* Bandwidth estimation */
	40	u32 minB;
	41	u32 maxB;
	42	u32 old_maxB;
	43	u32 Bi;
	44	u32 lasttime;
	45	};
	46
50bf3e22 BE	47	static inline u32 htcp_cong_time(struct htcp *ca)
	48	{
	49	return jiffies - ca->last_cong;
	50	}
	51
	52	static inline u32 htcp_ccount(struct htcp *ca)
	53	{
	54	return htcp_cong_time(ca)/ca->minRTT;
	55	}
	56
a7868ea6 BE	57	static inline void htcp_reset(struct htcp *ca)
a7868ea6 BE	58	{
50bf3e22	59	ca->undo_last_cong = ca->last_cong;
a7868ea6 BE	60	ca->undo_maxRTT = ca->maxRTT;
	61	ca->undo_old_maxB = ca->old_maxB;
	62
50bf3e22	63	ca->last_cong = jiffies;
a7868ea6 BE	64	}
a7868ea6 BE	65
6687e988	66	static u32 htcp_cwnd_undo(struct sock *sk)
a7868ea6	67	{
6687e988 ACM	68	const struct tcp_sock *tp = tcp_sk(sk);
6687e988 ACM	69	struct htcp *ca = inet_csk_ca(sk);
50bf3e22	70	ca->last_cong = ca->undo_last_cong;
a7868ea6 BE	71	ca->maxRTT = ca->undo_maxRTT;
	72	ca->old_maxB = ca->undo_old_maxB;
	73	return max(tp->snd_cwnd, (tp->snd_ssthresh<<7)/ca->beta);
	74	}
	75
6687e988	76	static inline void measure_rtt(struct sock *sk)
a7868ea6	77	{
6687e988 ACM	78	const struct inet_connection_sock *icsk = inet_csk(sk);
	79	const struct tcp_sock *tp = tcp_sk(sk);
	80	struct htcp *ca = inet_csk_ca(sk);
a7868ea6 BE	81	u32 srtt = tp->srtt>>3;
	82
	83	/* keep track of minimum RTT seen so far, minRTT is zero at first */
	84	if (ca->minRTT > srtt \|\| !ca->minRTT)
	85	ca->minRTT = srtt;
	86
	87	/* max RTT */
50bf3e22	88	if (icsk->icsk_ca_state == TCP_CA_Open && tp->snd_ssthresh < 0xFFFF && htcp_ccount(ca) > 3) {
a7868ea6 BE	89	if (ca->maxRTT < ca->minRTT)
a7868ea6 BE	90	ca->maxRTT = ca->minRTT;
c33ad6e4	91	if (ca->maxRTT < srtt && srtt <= ca->maxRTT+msecs_to_jiffies(20))
a7868ea6 BE	92	ca->maxRTT = srtt;
	93	}
	94	}
	95
6687e988	96	static void measure_achieved_throughput(struct sock *sk, u32 pkts_acked)
a7868ea6	97	{
6687e988 ACM	98	const struct inet_connection_sock *icsk = inet_csk(sk);
	99	const struct tcp_sock *tp = tcp_sk(sk);
	100	struct htcp *ca = inet_csk_ca(sk);
a7868ea6 BE	101	u32 now = tcp_time_stamp;
a7868ea6 BE	102
0bc6d90b BE	103	if (icsk->icsk_ca_state == TCP_CA_Open)
	104	ca->pkts_acked = pkts_acked;
	105
	106	if (!use_bandwidth_switch)
	107	return;
	108
a7868ea6	109	/* achieved throughput calculations */
6687e988 ACM	110	if (icsk->icsk_ca_state != TCP_CA_Open &&
6687e988 ACM	111	icsk->icsk_ca_state != TCP_CA_Disorder) {
a7868ea6 BE	112	ca->packetcount = 0;
	113	ca->lasttime = now;
	114	return;
	115	}
	116
	117	ca->packetcount += pkts_acked;
	118
	119	if (ca->packetcount >= tp->snd_cwnd - (ca->alpha>>7? : 1)
	120	&& now - ca->lasttime >= ca->minRTT
	121	&& ca->minRTT > 0) {
	122	__u32 cur_Bi = ca->packetcount*HZ/(now - ca->lasttime);
50bf3e22	123	if (htcp_ccount(ca) <= 3) {
a7868ea6 BE	124	/* just after backoff */
	125	ca->minB = ca->maxB = ca->Bi = cur_Bi;
	126	} else {
	127	ca->Bi = (3*ca->Bi + cur_Bi)/4;
	128	if (ca->Bi > ca->maxB)
	129	ca->maxB = ca->Bi;
	130	if (ca->minB > ca->maxB)
	131	ca->minB = ca->maxB;
	132	}
	133	ca->packetcount = 0;
	134	ca->lasttime = now;
	135	}
	136	}
	137
	138	static inline void htcp_beta_update(struct htcp *ca, u32 minRTT, u32 maxRTT)
	139	{
	140	if (use_bandwidth_switch) {
	141	u32 maxB = ca->maxB;
	142	u32 old_maxB = ca->old_maxB;
	143	ca->old_maxB = ca->maxB;
	144
	145	if (!between(5maxB, 4old_maxB, 6*old_maxB)) {
	146	ca->beta = BETA_MIN;
	147	ca->modeswitch = 0;
	148	return;
	149	}
	150	}
	151
c33ad6e4	152	if (ca->modeswitch && minRTT > msecs_to_jiffies(10) && maxRTT) {
a7868ea6 BE	153	ca->beta = (minRTT<<7)/maxRTT;
	154	if (ca->beta < BETA_MIN)
	155	ca->beta = BETA_MIN;
	156	else if (ca->beta > BETA_MAX)
	157	ca->beta = BETA_MAX;
	158	} else {
	159	ca->beta = BETA_MIN;
	160	ca->modeswitch = 1;
	161	}
	162	}
	163
	164	static inline void htcp_alpha_update(struct htcp *ca)
	165	{
	166	u32 minRTT = ca->minRTT;
	167	u32 factor = 1;
50bf3e22	168	u32 diff = htcp_cong_time(ca);
a7868ea6 BE	169
	170	if (diff > HZ) {
	171	diff -= HZ;
	172	factor = 1+ ( 10diff + ((diff/2)(diff/2)/HZ) )/HZ;
	173	}
	174
	175	if (use_rtt_scaling && minRTT) {
	176	u32 scale = (HZ<<3)/(10*minRTT);
	177	scale = min(max(scale, 1U<<2), 10U<<3); /* clamping ratio to interval [0.5,10]<<3 */
	178	factor = (factor<<3)/scale;
	179	if (!factor)
	180	factor = 1;
	181	}
	182
	183	ca->alpha = 2factor((1<<7)-ca->beta);
	184	if (!ca->alpha)
	185	ca->alpha = ALPHA_BASE;
	186	}
	187
	188	/* After we have the rtt data to calculate beta, we'd still prefer to wait one
	189	* rtt before we adjust our beta to ensure we are working from a consistent
	190	* data.
	191	*
	192	* This function should be called when we hit a congestion event since only at
	193	* that point do we really have a real sense of maxRTT (the queues en route
	194	* were getting just too full now).
	195	*/
6687e988	196	static void htcp_param_update(struct sock *sk)
a7868ea6	197	{
6687e988	198	struct htcp *ca = inet_csk_ca(sk);
a7868ea6 BE	199	u32 minRTT = ca->minRTT;
	200	u32 maxRTT = ca->maxRTT;
	201
	202	htcp_beta_update(ca, minRTT, maxRTT);
	203	htcp_alpha_update(ca);
	204
	205	/* add slowly fading memory for maxRTT to accommodate routing changes etc */
	206	if (minRTT > 0 && maxRTT > minRTT)
	207	ca->maxRTT = minRTT + ((maxRTT-minRTT)*95)/100;
	208	}
	209
6687e988	210	static u32 htcp_recalc_ssthresh(struct sock *sk)
a7868ea6	211	{
6687e988 ACM	212	const struct tcp_sock *tp = tcp_sk(sk);
	213	const struct htcp *ca = inet_csk_ca(sk);
	214	htcp_param_update(sk);
a7868ea6 BE	215	return max((tp->snd_cwnd * ca->beta) >> 7, 2U);
	216	}
	217
6687e988	218	static void htcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
a7868ea6 BE	219	u32 in_flight, int data_acked)
a7868ea6 BE	220	{
6687e988 ACM	221	struct tcp_sock *tp = tcp_sk(sk);
6687e988 ACM	222	struct htcp *ca = inet_csk_ca(sk);
a7868ea6	223
f4805ede	224	if (!tcp_is_cwnd_limited(sk, in_flight))
a7868ea6 BE	225	return;
a7868ea6 BE	226
e905a9ed	227	if (tp->snd_cwnd <= tp->snd_ssthresh)
7faffa1c SH	228	tcp_slow_start(tp);
	229	else {
	230
6687e988	231	measure_rtt(sk);
a7868ea6	232
7faffa1c	233	/* In dangerous area, increase slowly.
a7868ea6 BE	234	* In theory this is tp->snd_cwnd += alpha / tp->snd_cwnd
a7868ea6 BE	235	*/
0bc6d90b	236	if ((tp->snd_cwnd_cnt * ca->alpha)>>7 >= tp->snd_cwnd) {
a7868ea6 BE	237	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
	238	tp->snd_cwnd++;
	239	tp->snd_cwnd_cnt = 0;
50bf3e22	240	htcp_alpha_update(ca);
0bc6d90b BE	241	} else
	242	tp->snd_cwnd_cnt += ca->pkts_acked;
	243
	244	ca->pkts_acked = 1;
a7868ea6 BE	245	}
	246	}
	247
6687e988	248	static void htcp_init(struct sock *sk)
a7868ea6	249	{
6687e988	250	struct htcp *ca = inet_csk_ca(sk);
a7868ea6 BE	251
	252	memset(ca, 0, sizeof(struct htcp));
	253	ca->alpha = ALPHA_BASE;
	254	ca->beta = BETA_MIN;
0bc6d90b	255	ca->pkts_acked = 1;
50bf3e22	256	ca->last_cong = jiffies;
a7868ea6 BE	257	}
a7868ea6 BE	258
6687e988	259	static void htcp_state(struct sock *sk, u8 new_state)
a7868ea6 BE	260	{
a7868ea6 BE	261	switch (new_state) {
50bf3e22 BE	262	case TCP_CA_Open:
	263	{
	264	struct htcp *ca = inet_csk_ca(sk);
	265	ca->last_cong = jiffies;
	266	}
	267	break;
a7868ea6 BE	268	case TCP_CA_CWR:
	269	case TCP_CA_Recovery:
	270	case TCP_CA_Loss:
6687e988	271	htcp_reset(inet_csk_ca(sk));
a7868ea6 BE	272	break;
	273	}
	274	}
	275
	276	static struct tcp_congestion_ops htcp = {
	277	.init = htcp_init,
	278	.ssthresh = htcp_recalc_ssthresh,
a7868ea6 BE	279	.cong_avoid = htcp_cong_avoid,
	280	.set_state = htcp_state,
	281	.undo_cwnd = htcp_cwnd_undo,
	282	.pkts_acked = measure_achieved_throughput,
	283	.owner = THIS_MODULE,
	284	.name = "htcp",
	285	};
	286
	287	static int __init htcp_register(void)
	288	{
74975d40	289	BUILD_BUG_ON(sizeof(struct htcp) > ICSK_CA_PRIV_SIZE);
a7868ea6	290	BUILD_BUG_ON(BETA_MIN >= BETA_MAX);
a7868ea6 BE	291	return tcp_register_congestion_control(&htcp);
	292	}
	293
	294	static void __exit htcp_unregister(void)
	295	{
	296	tcp_unregister_congestion_control(&htcp);
	297	}
	298
	299	module_init(htcp_register);
	300	module_exit(htcp_unregister);
	301
	302	MODULE_AUTHOR("Baruch Even");
	303	MODULE_LICENSE("GPL");
	304	MODULE_DESCRIPTION("H-TCP");