1 files changed, 34 insertions, 11 deletions

diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 62f775c..34340c9 100644
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -39,7 +39,7 @@
 
 /* Number of delay samples for detecting the increase of delay */
 #define HYSTART_MIN_SAMPLES	8
-#define HYSTART_DELAY_MIN	(2U<<3)
+#define HYSTART_DELAY_MIN	(4U<<3)
 #define HYSTART_DELAY_MAX	(16U<<3)
 #define HYSTART_DELAY_THRESH(x)	clamp(x, HYSTART_DELAY_MIN, HYSTART_DELAY_MAX)
 
@@ -52,6 +52,7 @@ static int tcp_friendliness __read_mostly = 1;
 static int hystart __read_mostly = 1;
 static int hystart_detect __read_mostly = HYSTART_ACK_TRAIN | HYSTART_DELAY;
 static int hystart_low_window __read_mostly = 16;
+static int hystart_ack_delta __read_mostly = 2;
 
 static u32 cube_rtt_scale __read_mostly;
 static u32 beta_scale __read_mostly;
@@ -75,6 +76,8 @@ MODULE_PARM_DESC(hystart_detect, "hyrbrid slow start detection mechanisms"
 		 " 1: packet-train 2: delay 3: both packet-train and delay");
 module_param(hystart_low_window, int, 0644);
 MODULE_PARM_DESC(hystart_low_window, "lower bound cwnd for hybrid slow start");
+module_param(hystart_ack_delta, int, 0644);
+MODULE_PARM_DESC(hystart_ack_delta, "spacing between ack's indicating train (msecs)");
 
 /* BIC TCP Parameters */
 struct bictcp {
@@ -85,7 +88,7 @@ struct bictcp {
 	u32	last_time;	/* time when updated last_cwnd */
 	u32	bic_origin_point;/* origin point of bic function */
 	u32	bic_K;		/* time to origin point from the beginning of the current epoch */
-	u32	delay_min;	/* min delay */
+	u32	delay_min;	/* min delay (msec << 3) */
 	u32	epoch_start;	/* beginning of an epoch */
 	u32	ack_cnt;	/* number of acks */
 	u32	tcp_cwnd;	/* estimated tcp cwnd */
@@ -95,7 +98,7 @@ struct bictcp {
 	u8	found;		/* the exit point is found? */
 	u32	round_start;	/* beginning of each round */
 	u32	end_seq;	/* end_seq of the round */
-	u32	last_jiffies;	/* last time when the ACK spacing is close */
+	u32	last_ack;	/* last time when the ACK spacing is close */
 	u32	curr_rtt;	/* the minimum rtt of current round */
 };
 
@@ -116,12 +119,21 @@ static inline void bictcp_reset(struct bictcp *ca)
 	ca->found = 0;
 }
 
+static inline u32 bictcp_clock(void)
+{
+#if HZ < 1000
+	return ktime_to_ms(ktime_get_real());
+#else
+	return jiffies_to_msecs(jiffies);
+#endif
+}
+
 static inline void bictcp_hystart_reset(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct bictcp *ca = inet_csk_ca(sk);
 
-	ca->round_start = ca->last_jiffies = jiffies;
+	ca->round_start = ca->last_ack = bictcp_clock();
 	ca->end_seq = tp->snd_nxt;
 	ca->curr_rtt = 0;
 	ca->sample_cnt = 0;
@@ -236,8 +248,8 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd)
 	 */
 
 	/* change the unit from HZ to bictcp_HZ */
-	t = ((tcp_time_stamp + (ca->delay_min>>3) - ca->epoch_start)
-	     << BICTCP_HZ) / HZ;
+	t = ((tcp_time_stamp + msecs_to_jiffies(ca->delay_min>>3)
+	      - ca->epoch_start) << BICTCP_HZ) / HZ;
 
 	if (t < ca->bic_K)		/* t - K */
 		offs = ca->bic_K - t;
@@ -258,6 +270,13 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd)
 		ca->cnt = 100 * cwnd;              /* very small increment*/
 	}
 
+	/*
+	 * The initial growth of cubic function may be too conservative
+	 * when the available bandwidth is still unknown.
+	 */
+	if (ca->loss_cwnd == 0 && ca->cnt > 20)
+		ca->cnt = 20;	/* increase cwnd 5% per RTT */
+
 	/* TCP Friendly */
 	if (tcp_friendliness) {
 		u32 scale = beta_scale;
@@ -339,12 +358,12 @@ static void hystart_update(struct sock *sk, u32 delay)
 	struct bictcp *ca = inet_csk_ca(sk);
 
 	if (!(ca->found & hystart_detect)) {
-		u32 curr_jiffies = jiffies;
+		u32 now = bictcp_clock();
 
 		/* first detection parameter - ack-train detection */
-		if (curr_jiffies - ca->last_jiffies <= msecs_to_jiffies(2)) {
-			ca->last_jiffies = curr_jiffies;
-			if (curr_jiffies - ca->round_start >= ca->delay_min>>4)
+		if ((s32)(now - ca->last_ack) <= hystart_ack_delta) {
+			ca->last_ack = now;
+			if ((s32)(now - ca->round_start) > ca->delay_min >> 4)
 				ca->found |= HYSTART_ACK_TRAIN;
 		}
 
@@ -391,7 +410,7 @@ static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt_us)
 	if ((s32)(tcp_time_stamp - ca->epoch_start) < HZ)
 		return;
 
-	delay = usecs_to_jiffies(rtt_us) << 3;
+	delay = (rtt_us << 3) / USEC_PER_MSEC;
 	if (delay == 0)
 		delay = 1;
 
@@ -447,6 +466,10 @@ static int __init cubictcp_register(void)
 	/* divide by bic_scale and by constant Srtt (100ms) */
 	do_div(cube_factor, bic_scale * 10);
 
+	/* hystart needs ms clock resolution */
+	if (hystart && HZ < 1000)
+		cubictcp.flags |= TCP_CONG_RTT_STAMP;
+
 	return tcp_register_congestion_control(&cubictcp);
 }