1 files changed, 42 insertions, 14 deletions

diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 71d5f2f29fa6..f376b05cca81 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 {
@@ -85,17 +88,18 @@ 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 */
 #define ACK_RATIO_SHIFT 4
+#define ACK_RATIO_LIMIT (32u << ACK_RATIO_SHIFT)
         u16     delayed_ack;    /* estimate the ratio of Packets/ACKs << 4 */
         u8      sample_cnt;     /* number of samples to decide curr_rtt */
         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 +120,21 @@ 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 +249,8 @@ 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 +271,13 @@ 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 +359,12 @@ 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;
                 }
 
@@ -379,8 +399,12 @@ static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt_us)
         u32 delay;
 
         if (icsk->icsk_ca_state == TCP_CA_Open) {
-                cnt -= ca->delayed_ack >> ACK_RATIO_SHIFT;
-                ca->delayed_ack += cnt;
+                u32 ratio = ca->delayed_ack;
+
+                ratio -= ca->delayed_ack >> ACK_RATIO_SHIFT;
+                ratio += cnt;
+
+                ca->delayed_ack = min(ratio, ACK_RATIO_LIMIT);
         }
 
         /* Some calls are for duplicates without timetamps */
@@ -391,7 +415,7 @@ 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;
 
@@ -405,7 +429,7 @@ static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt_us)
                 hystart_update(sk, delay);
 }
 
-static struct tcp_congestion_ops cubictcp = {
+static struct tcp_congestion_ops cubictcp __read_mostly = {
         .init           = bictcp_init,
         .ssthresh       = bictcp_recalc_ssthresh,
         .cong_avoid     = bictcp_cong_avoid,
@@ -447,6 +471,10 @@ 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);
 }