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Commit 50bf3e22 authored by Baruch Even's avatar Baruch Even Committed by David S. Miller
Browse files

[TCP] H-TCP: Better time accounting 



Instead of estimating the time since the last congestion event, count
it directly.

Signed-off-by: default avatarBaruch Even <baruch@ev-en.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0bc6d90b

net/ipv4/tcp_htcp.c

+26 −18
Original line number Diff line number Diff line
@@ -27,13 +27,12 @@ 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;

	u32	last_cong;	/* Time since last congestion event end */

	u32	undo_last_cong;

	u16	pkts_acked;

	u32	packetcount;

	u32	minRTT;

	u32	maxRTT;

	u32	snd_cwnd_cnt2;



	u32	undo_maxRTT;

	u32	undo_old_maxB;
@@ -46,21 +45,30 @@ struct htcp { 
	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_ccount = ca->ccount;

	ca->undo_last_cong = ca->last_cong;

	ca->undo_maxRTT = ca->maxRTT;

	ca->undo_old_maxB = ca->old_maxB;



	ca->ccount = 0;

	ca->snd_cwnd_cnt2 = 0;

	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->ccount = ca->undo_ccount;

	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);
@@ -78,7 +86,7 @@ static inline void measure_rtt(struct sock *sk) 
		ca->minRTT = srtt;



	/* max RTT */

	if (icsk->icsk_ca_state == TCP_CA_Open && tp->snd_ssthresh < 0xFFFF && ca->ccount > 3) {

	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))
@@ -113,7 +121,7 @@ static void measure_achieved_throughput(struct sock *sk, u32 pkts_acked) 
			&& now - ca->lasttime >= ca->minRTT

			&& ca->minRTT > 0) {

		__u32 cur_Bi = ca->packetcount*HZ/(now - ca->lasttime);

		if (ca->ccount <= 3) {

		if (htcp_ccount(ca) <= 3) {

			/* just after backoff */

			ca->minB = ca->maxB = ca->Bi = cur_Bi;

		} else {
@@ -158,7 +166,7 @@ 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 */

	u32 diff = htcp_cong_time(ca);



	if (diff > HZ) {

		diff -= HZ;
@@ -223,14 +231,6 @@ static void htcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt, 


		measure_rtt(sk);



		/* 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 -= tp->snd_cwnd;

			htcp_alpha_update(ca);

		} else

			ca->snd_cwnd_cnt2 += ca->pkts_acked;



		/* In dangerous area, increase slowly.

		 * In theory this is tp->snd_cwnd += alpha / tp->snd_cwnd

		 */
@@ -238,6 +238,7 @@ static void htcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt, 
			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;
@@ -261,11 +262,18 @@ static void htcp_init(struct sock *sk) 
	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: