From 018da8f44c066d5fc390011b8c953135f973b3a9 Mon Sep 17 00:00:00 2001 From: Stephen Hemminger Date: Tue, 13 Dec 2005 23:13:00 -0800 Subject: [PATCH] [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 Signed-off-by: David S. Miller --- net/ipv4/tcp_bic.c | 81 +--------------------------------------------- 1 file changed, 1 insertion(+), 80 deletions(-) diff --git a/net/ipv4/tcp_bic.c b/net/ipv4/tcp_bic.c index 1d0cd86621b1..cf8c75f08efa 100644 --- a/net/ipv4/tcp_bic.c +++ b/net/ipv4/tcp_bic.c @@ -30,8 +30,6 @@ static int fast_convergence = 1; static int max_increment = 16; static int low_window = 14; static int beta = 819; /* = 819/1024 (BICTCP_BETA_SCALE) */ -static int low_utilization_threshold = 153; -static int low_utilization_period = 2; static int initial_ssthresh = 100; static int smooth_part = 20; @@ -43,10 +41,6 @@ module_param(low_window, int, 0644); MODULE_PARM_DESC(low_window, "lower bound on congestion window (for TCP friendliness)"); module_param(beta, int, 0644); MODULE_PARM_DESC(beta, "beta for multiplicative increase"); -module_param(low_utilization_threshold, int, 0644); -MODULE_PARM_DESC(low_utilization_threshold, "percent (scaled by 1024) for low utilization mode"); -module_param(low_utilization_period, int, 0644); -MODULE_PARM_DESC(low_utilization_period, "if average delay exceeds then goto to low utilization mode (seconds)"); module_param(initial_ssthresh, int, 0644); MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold"); module_param(smooth_part, int, 0644); @@ -60,11 +54,6 @@ struct bictcp { u32 loss_cwnd; /* congestion window at last loss */ u32 last_cwnd; /* the last snd_cwnd */ u32 last_time; /* time when updated last_cwnd */ - u32 delay_min; /* min delay */ - u32 delay_max; /* max delay */ - u32 last_delay; - u8 low_utilization;/* 0: high; 1: low */ - u32 low_utilization_start; /* starting time of low utilization detection*/ u32 epoch_start; /* beginning of an epoch */ #define ACK_RATIO_SHIFT 4 u32 delayed_ack; /* estimate the ratio of Packets/ACKs << 4 */ @@ -77,11 +66,6 @@ static inline void bictcp_reset(struct bictcp *ca) ca->loss_cwnd = 0; ca->last_cwnd = 0; ca->last_time = 0; - ca->delay_min = 0; - ca->delay_max = 0; - ca->last_delay = 0; - ca->low_utilization = 0; - ca->low_utilization_start = 0; ca->epoch_start = 0; ca->delayed_ack = 2 << ACK_RATIO_SHIFT; } @@ -143,8 +127,7 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd) } /* if in slow start or link utilization is very low */ - if ( ca->loss_cwnd == 0 || - (cwnd > ca->loss_cwnd && ca->low_utilization)) { + if (ca->loss_cwnd == 0) { if (ca->cnt > 20) /* increase cwnd 5% per RTT */ ca->cnt = 20; } @@ -154,69 +137,12 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd) ca->cnt = 1; } - -/* Detect low utilization in congestion avoidance */ -static inline void bictcp_low_utilization(struct sock *sk, int flag) -{ - const struct tcp_sock *tp = tcp_sk(sk); - struct bictcp *ca = inet_csk_ca(sk); - u32 dist, delay; - - /* No time stamp */ - if (!(tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) || - /* Discard delay samples right after fast recovery */ - tcp_time_stamp < ca->epoch_start + HZ || - /* this delay samples may not be accurate */ - flag == 0) { - ca->last_delay = 0; - goto notlow; - } - - delay = ca->last_delay<<3; /* use the same scale as tp->srtt*/ - ca->last_delay = tcp_time_stamp - tp->rx_opt.rcv_tsecr; - if (delay == 0) /* no previous delay sample */ - goto notlow; - - /* first time call or link delay decreases */ - if (ca->delay_min == 0 || ca->delay_min > delay) { - ca->delay_min = ca->delay_max = delay; - goto notlow; - } - - if (ca->delay_max < delay) - ca->delay_max = delay; - - /* utilization is low, if avg delay < dist*threshold - for checking_period time */ - dist = ca->delay_max - ca->delay_min; - if (dist <= ca->delay_min>>6 || - tp->srtt - ca->delay_min >= (dist*low_utilization_threshold)>>10) - goto notlow; - - if (ca->low_utilization_start == 0) { - ca->low_utilization = 0; - ca->low_utilization_start = tcp_time_stamp; - } else if ((s32)(tcp_time_stamp - ca->low_utilization_start) - > low_utilization_period*HZ) { - ca->low_utilization = 1; - } - - return; - - notlow: - ca->low_utilization = 0; - ca->low_utilization_start = 0; - -} - static void bictcp_cong_avoid(struct sock *sk, u32 ack, u32 seq_rtt, u32 in_flight, int data_acked) { struct tcp_sock *tp = tcp_sk(sk); struct bictcp *ca = inet_csk_ca(sk); - bictcp_low_utilization(sk, data_acked); - if (!tcp_is_cwnd_limited(sk, in_flight)) return; @@ -249,11 +175,6 @@ static u32 bictcp_recalc_ssthresh(struct sock *sk) ca->epoch_start = 0; /* end of epoch */ - /* in case of wrong delay_max*/ - if (ca->delay_min > 0 && ca->delay_max > ca->delay_min) - ca->delay_max = ca->delay_min - + ((ca->delay_max - ca->delay_min)* 90) / 100; - /* Wmax and fast convergence */ if (tp->snd_cwnd < ca->last_max_cwnd && fast_convergence) ca->last_max_cwnd = (tp->snd_cwnd * (BICTCP_BETA_SCALE + beta))