net/ipv4/tcp_htcp.c - kernel/msm - Gitiles

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

 static int use_bandwidth_switch __read_mostly = 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(const struct htcp *ca)
 {
 	return jiffies - ca->last_cong;
 }

 static inline u32 htcp_ccount(const 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, u32 srtt)
 {
 	const struct inet_connection_sock *icsk = inet_csk(sk);
 	struct htcp *ca = inet_csk_ca(sk);

 	/* 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) {
 		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, s32 rtt)
 {
 	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 (rtt > 0)
 		measure_rtt(sk, usecs_to_jiffies(rtt));

 	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);

 		/* clamping ratio to interval [0.5,10]<<3 */
 		scale = min(max(scale, 1U << 2), 10U << 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 */
 	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 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 {
 		/* 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");
	/*
	* 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 __read_mostly = 1;
	module_param(use_rtt_scaling, int, 0644);
	MODULE_PARM_DESC(use_rtt_scaling, "turn on/off RTT scaling");

	static int use_bandwidth_switch __read_mostly = 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(const struct htcp *ca)
	{
	return jiffies - ca->last_cong;
	}

	static inline u32 htcp_ccount(const 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, u32 srtt)
	{
	const struct inet_connection_sock *icsk = inet_csk(sk);
	struct htcp *ca = inet_csk_ca(sk);

	/* 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) {
	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, s32 rtt)
	{
	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 (rtt > 0)
	measure_rtt(sk, usecs_to_jiffies(rtt));

	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);

	/* clamping ratio to interval [0.5,10]<<3 */
	scale = min(max(scale, 1U << 2), 10U << 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 */
	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 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 {
	/* 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");