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