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Commit f1722a1b authored by Yuchung Cheng's avatar Yuchung Cheng Committed by David S. Miller
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tcp: consolidate congestion control undo functions 



Most TCP congestion controls are using identical logic to undo
cwnd except BBR. This patch consolidates these similar functions
to the one used currently by Reno and others.

Suggested-by: default avatarNeal Cardwell <ncardwell@google.com>
Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
Signed-off-by: default avatarNeal Cardwell <ncardwell@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4faf7839

net/ipv4/tcp_bic.c

+1 −13
Original line number Diff line number Diff line
@@ -49,7 +49,6 @@ MODULE_PARM_DESC(smooth_part, "log(B/(B*Smin))/log(B/(B-1))+B, # of RTT from Wma 
struct bictcp {

	u32	cnt;		/* increase cwnd by 1 after ACKs */

	u32	last_max_cwnd;	/* last maximum snd_cwnd */

	u32	loss_cwnd;	/* congestion window at last loss */

	u32	last_cwnd;	/* the last snd_cwnd */

	u32	last_time;	/* time when updated last_cwnd */

	u32	epoch_start;	/* beginning of an epoch */
@@ -72,7 +71,6 @@ static void bictcp_init(struct sock *sk) 
	struct bictcp *ca = inet_csk_ca(sk);



	bictcp_reset(ca);

	ca->loss_cwnd = 0;



	if (initial_ssthresh)

		tcp_sk(sk)->snd_ssthresh = initial_ssthresh;
@@ -172,22 +170,12 @@ static u32 bictcp_recalc_ssthresh(struct sock *sk) 
	else

		ca->last_max_cwnd = tp->snd_cwnd;



	ca->loss_cwnd = tp->snd_cwnd;



	if (tp->snd_cwnd <= low_window)

		return max(tp->snd_cwnd >> 1U, 2U);

	else

		return max((tp->snd_cwnd * beta) / BICTCP_BETA_SCALE, 2U);

}



static u32 bictcp_undo_cwnd(struct sock *sk)

{

	const struct tcp_sock *tp = tcp_sk(sk);

	const struct bictcp *ca = inet_csk_ca(sk);



	return max(tp->snd_cwnd, ca->loss_cwnd);

}



static void bictcp_state(struct sock *sk, u8 new_state)

{

	if (new_state == TCP_CA_Loss)
@@ -214,7 +202,7 @@ static struct tcp_congestion_ops bictcp __read_mostly = { 
	.ssthresh	= bictcp_recalc_ssthresh,

	.cong_avoid	= bictcp_cong_avoid,

	.set_state	= bictcp_state,

	.undo_cwnd	= bictcp_undo_cwnd,

	.undo_cwnd	= tcp_reno_undo_cwnd,

	.pkts_acked     = bictcp_acked,

	.owner		= THIS_MODULE,

	.name		= "bic",

net/ipv4/tcp_cdg.c

+1 −11
Original line number Diff line number Diff line
@@ -85,7 +85,6 @@ struct cdg { 
	u8  state;

	u8  delack;

	u32 rtt_seq;

	u32 undo_cwnd;

	u32 shadow_wnd;

	u16 backoff_cnt;

	u16 sample_cnt;
@@ -330,8 +329,6 @@ static u32 tcp_cdg_ssthresh(struct sock *sk) 
	struct cdg *ca = inet_csk_ca(sk);

	struct tcp_sock *tp = tcp_sk(sk);



	ca->undo_cwnd = tp->snd_cwnd;



	if (ca->state == CDG_BACKOFF)

		return max(2U, (tp->snd_cwnd * min(1024U, backoff_beta)) >> 10);
@@ -344,13 +341,6 @@ static u32 tcp_cdg_ssthresh(struct sock *sk) 
	return max(2U, tp->snd_cwnd >> 1);

}



static u32 tcp_cdg_undo_cwnd(struct sock *sk)

{

	struct cdg *ca = inet_csk_ca(sk);



	return max(tcp_sk(sk)->snd_cwnd, ca->undo_cwnd);

}



static void tcp_cdg_cwnd_event(struct sock *sk, const enum tcp_ca_event ev)

{

	struct cdg *ca = inet_csk_ca(sk);
@@ -403,7 +393,7 @@ struct tcp_congestion_ops tcp_cdg __read_mostly = { 
	.cong_avoid = tcp_cdg_cong_avoid,

	.cwnd_event = tcp_cdg_cwnd_event,

	.pkts_acked = tcp_cdg_acked,

	.undo_cwnd = tcp_cdg_undo_cwnd,

	.undo_cwnd = tcp_reno_undo_cwnd,

	.ssthresh = tcp_cdg_ssthresh,

	.release = tcp_cdg_release,

	.init = tcp_cdg_init,

net/ipv4/tcp_cubic.c

+1 −12
Original line number Diff line number Diff line
@@ -83,7 +83,6 @@ MODULE_PARM_DESC(hystart_ack_delta, "spacing between ack's indicating train (mse 
struct bictcp {

	u32	cnt;		/* increase cwnd by 1 after ACKs */

	u32	last_max_cwnd;	/* last maximum snd_cwnd */

	u32	loss_cwnd;	/* congestion window at last loss */

	u32	last_cwnd;	/* the last snd_cwnd */

	u32	last_time;	/* time when updated last_cwnd */

	u32	bic_origin_point;/* origin point of bic function */
@@ -142,7 +141,6 @@ static void bictcp_init(struct sock *sk) 
	struct bictcp *ca = inet_csk_ca(sk);



	bictcp_reset(ca);

	ca->loss_cwnd = 0;



	if (hystart)

		bictcp_hystart_reset(sk);
@@ -366,18 +364,9 @@ static u32 bictcp_recalc_ssthresh(struct sock *sk) 
	else

		ca->last_max_cwnd = tp->snd_cwnd;



	ca->loss_cwnd = tp->snd_cwnd;



	return max((tp->snd_cwnd * beta) / BICTCP_BETA_SCALE, 2U);

}



static u32 bictcp_undo_cwnd(struct sock *sk)

{

	struct bictcp *ca = inet_csk_ca(sk);



	return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);

}



static void bictcp_state(struct sock *sk, u8 new_state)

{

	if (new_state == TCP_CA_Loss) {
@@ -470,7 +459,7 @@ static struct tcp_congestion_ops cubictcp __read_mostly = { 
	.ssthresh	= bictcp_recalc_ssthresh,

	.cong_avoid	= bictcp_cong_avoid,

	.set_state	= bictcp_state,

	.undo_cwnd	= bictcp_undo_cwnd,

	.undo_cwnd	= tcp_reno_undo_cwnd,

	.cwnd_event	= bictcp_cwnd_event,

	.pkts_acked     = bictcp_acked,

	.owner		= THIS_MODULE,

net/ipv4/tcp_highspeed.c

+1 −10
Original line number Diff line number Diff line
@@ -94,7 +94,6 @@ static const struct hstcp_aimd_val { 


struct hstcp {

	u32	ai;

	u32	loss_cwnd;

};



static void hstcp_init(struct sock *sk)
@@ -153,22 +152,14 @@ static u32 hstcp_ssthresh(struct sock *sk) 
	const struct tcp_sock *tp = tcp_sk(sk);

	struct hstcp *ca = inet_csk_ca(sk);



	ca->loss_cwnd = tp->snd_cwnd;

	/* Do multiplicative decrease */

	return max(tp->snd_cwnd - ((tp->snd_cwnd * hstcp_aimd_vals[ca->ai].md) >> 8), 2U);

}



static u32 hstcp_cwnd_undo(struct sock *sk)

{

	const struct hstcp *ca = inet_csk_ca(sk);



	return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);

}



static struct tcp_congestion_ops tcp_highspeed __read_mostly = {

	.init		= hstcp_init,

	.ssthresh	= hstcp_ssthresh,

	.undo_cwnd	= hstcp_cwnd_undo,

	.undo_cwnd	= tcp_reno_undo_cwnd,

	.cong_avoid	= hstcp_cong_avoid,



	.owner		= THIS_MODULE,

net/ipv4/tcp_illinois.c

+1 −10
Original line number Diff line number Diff line
@@ -48,7 +48,6 @@ struct illinois { 
	u32	end_seq;	/* right edge of current RTT */

	u32	alpha;		/* Additive increase */

	u32	beta;		/* Muliplicative decrease */

	u32	loss_cwnd;	/* cwnd on loss */

	u16	acked;		/* # packets acked by current ACK */

	u8	rtt_above;	/* average rtt has gone above threshold */

	u8	rtt_low;	/* # of rtts measurements below threshold */
@@ -297,18 +296,10 @@ static u32 tcp_illinois_ssthresh(struct sock *sk) 
	struct tcp_sock *tp = tcp_sk(sk);

	struct illinois *ca = inet_csk_ca(sk);



	ca->loss_cwnd = tp->snd_cwnd;

	/* Multiplicative decrease */

	return max(tp->snd_cwnd - ((tp->snd_cwnd * ca->beta) >> BETA_SHIFT), 2U);

}



static u32 tcp_illinois_cwnd_undo(struct sock *sk)

{

	const struct illinois *ca = inet_csk_ca(sk);



	return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);

}



/* Extract info for Tcp socket info provided via netlink. */

static size_t tcp_illinois_info(struct sock *sk, u32 ext, int *attr,

				union tcp_cc_info *info)
@@ -336,7 +327,7 @@ static size_t tcp_illinois_info(struct sock *sk, u32 ext, int *attr, 
static struct tcp_congestion_ops tcp_illinois __read_mostly = {

	.init		= tcp_illinois_init,

	.ssthresh	= tcp_illinois_ssthresh,

	.undo_cwnd	= tcp_illinois_cwnd_undo,

	.undo_cwnd	= tcp_reno_undo_cwnd,

	.cong_avoid	= tcp_illinois_cong_avoid,

	.set_state	= tcp_illinois_state,

	.get_info	= tcp_illinois_info,