[TCP] BIC: remove low utilization code.
The latest BICTCP patch at: http://www.csc.ncsu.edu:8080/faculty/rhee/export/bitcp/index_files/Page546.htm disables the low_utilization feature of BICTCP because it doesn't work in some cases. This patch removes it. Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -30,8 +30,6 @@ static int fast_convergence = 1;
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static int max_increment = 16;
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static int max_increment = 16;
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static int low_window = 14;
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static int low_window = 14;
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static int beta = 819; /* = 819/1024 (BICTCP_BETA_SCALE) */
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static int beta = 819; /* = 819/1024 (BICTCP_BETA_SCALE) */
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static int low_utilization_threshold = 153;
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static int low_utilization_period = 2;
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static int initial_ssthresh = 100;
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static int initial_ssthresh = 100;
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static int smooth_part = 20;
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static int smooth_part = 20;
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@ -43,10 +41,6 @@ module_param(low_window, int, 0644);
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MODULE_PARM_DESC(low_window, "lower bound on congestion window (for TCP friendliness)");
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MODULE_PARM_DESC(low_window, "lower bound on congestion window (for TCP friendliness)");
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module_param(beta, int, 0644);
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module_param(beta, int, 0644);
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MODULE_PARM_DESC(beta, "beta for multiplicative increase");
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MODULE_PARM_DESC(beta, "beta for multiplicative increase");
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module_param(low_utilization_threshold, int, 0644);
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MODULE_PARM_DESC(low_utilization_threshold, "percent (scaled by 1024) for low utilization mode");
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module_param(low_utilization_period, int, 0644);
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MODULE_PARM_DESC(low_utilization_period, "if average delay exceeds then goto to low utilization mode (seconds)");
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module_param(initial_ssthresh, int, 0644);
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module_param(initial_ssthresh, int, 0644);
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MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold");
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MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold");
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module_param(smooth_part, int, 0644);
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module_param(smooth_part, int, 0644);
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@ -60,11 +54,6 @@ struct bictcp {
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u32 loss_cwnd; /* congestion window at last loss */
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u32 loss_cwnd; /* congestion window at last loss */
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u32 last_cwnd; /* the last snd_cwnd */
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u32 last_cwnd; /* the last snd_cwnd */
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u32 last_time; /* time when updated last_cwnd */
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u32 last_time; /* time when updated last_cwnd */
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u32 delay_min; /* min delay */
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u32 delay_max; /* max delay */
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u32 last_delay;
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u8 low_utilization;/* 0: high; 1: low */
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u32 low_utilization_start; /* starting time of low utilization detection*/
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u32 epoch_start; /* beginning of an epoch */
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u32 epoch_start; /* beginning of an epoch */
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#define ACK_RATIO_SHIFT 4
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#define ACK_RATIO_SHIFT 4
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u32 delayed_ack; /* estimate the ratio of Packets/ACKs << 4 */
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u32 delayed_ack; /* estimate the ratio of Packets/ACKs << 4 */
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@ -77,11 +66,6 @@ static inline void bictcp_reset(struct bictcp *ca)
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ca->loss_cwnd = 0;
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ca->loss_cwnd = 0;
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ca->last_cwnd = 0;
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ca->last_cwnd = 0;
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ca->last_time = 0;
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ca->last_time = 0;
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ca->delay_min = 0;
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ca->delay_max = 0;
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ca->last_delay = 0;
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ca->low_utilization = 0;
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ca->low_utilization_start = 0;
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ca->epoch_start = 0;
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ca->epoch_start = 0;
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ca->delayed_ack = 2 << ACK_RATIO_SHIFT;
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ca->delayed_ack = 2 << ACK_RATIO_SHIFT;
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}
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}
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@ -143,8 +127,7 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd)
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}
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}
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/* if in slow start or link utilization is very low */
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/* if in slow start or link utilization is very low */
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if ( ca->loss_cwnd == 0 ||
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if (ca->loss_cwnd == 0) {
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(cwnd > ca->loss_cwnd && ca->low_utilization)) {
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if (ca->cnt > 20) /* increase cwnd 5% per RTT */
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if (ca->cnt > 20) /* increase cwnd 5% per RTT */
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ca->cnt = 20;
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ca->cnt = 20;
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}
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}
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@ -154,69 +137,12 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd)
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ca->cnt = 1;
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ca->cnt = 1;
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}
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}
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/* Detect low utilization in congestion avoidance */
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static inline void bictcp_low_utilization(struct sock *sk, int flag)
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{
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const struct tcp_sock *tp = tcp_sk(sk);
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struct bictcp *ca = inet_csk_ca(sk);
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u32 dist, delay;
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/* No time stamp */
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if (!(tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) ||
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/* Discard delay samples right after fast recovery */
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tcp_time_stamp < ca->epoch_start + HZ ||
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/* this delay samples may not be accurate */
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flag == 0) {
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ca->last_delay = 0;
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goto notlow;
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}
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delay = ca->last_delay<<3; /* use the same scale as tp->srtt*/
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ca->last_delay = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
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if (delay == 0) /* no previous delay sample */
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goto notlow;
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/* first time call or link delay decreases */
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if (ca->delay_min == 0 || ca->delay_min > delay) {
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ca->delay_min = ca->delay_max = delay;
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goto notlow;
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}
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if (ca->delay_max < delay)
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ca->delay_max = delay;
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/* utilization is low, if avg delay < dist*threshold
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for checking_period time */
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dist = ca->delay_max - ca->delay_min;
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if (dist <= ca->delay_min>>6 ||
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tp->srtt - ca->delay_min >= (dist*low_utilization_threshold)>>10)
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goto notlow;
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if (ca->low_utilization_start == 0) {
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ca->low_utilization = 0;
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ca->low_utilization_start = tcp_time_stamp;
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} else if ((s32)(tcp_time_stamp - ca->low_utilization_start)
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> low_utilization_period*HZ) {
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ca->low_utilization = 1;
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}
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return;
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notlow:
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ca->low_utilization = 0;
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ca->low_utilization_start = 0;
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}
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static void bictcp_cong_avoid(struct sock *sk, u32 ack,
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static void bictcp_cong_avoid(struct sock *sk, u32 ack,
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u32 seq_rtt, u32 in_flight, int data_acked)
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u32 seq_rtt, u32 in_flight, int data_acked)
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{
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{
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struct tcp_sock *tp = tcp_sk(sk);
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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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struct bictcp *ca = inet_csk_ca(sk);
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bictcp_low_utilization(sk, data_acked);
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if (!tcp_is_cwnd_limited(sk, in_flight))
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if (!tcp_is_cwnd_limited(sk, in_flight))
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return;
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return;
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@ -249,11 +175,6 @@ static u32 bictcp_recalc_ssthresh(struct sock *sk)
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ca->epoch_start = 0; /* end of epoch */
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ca->epoch_start = 0; /* end of epoch */
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/* in case of wrong delay_max*/
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if (ca->delay_min > 0 && ca->delay_max > ca->delay_min)
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ca->delay_max = ca->delay_min
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+ ((ca->delay_max - ca->delay_min)* 90) / 100;
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/* Wmax and fast convergence */
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/* Wmax and fast convergence */
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if (tp->snd_cwnd < ca->last_max_cwnd && fast_convergence)
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if (tp->snd_cwnd < ca->last_max_cwnd && fast_convergence)
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ca->last_max_cwnd = (tp->snd_cwnd * (BICTCP_BETA_SCALE + beta))
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ca->last_max_cwnd = (tp->snd_cwnd * (BICTCP_BETA_SCALE + beta))
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