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Commit 50bf3e22 authored by Baruch Even's avatar Baruch Even Committed by David S. Miller
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[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
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+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: