[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>
diff --git a/net/ipv4/tcp_bic.c b/net/ipv4/tcp_bic.c
index 1d0cd86..cf8c75f 100644
--- a/net/ipv4/tcp_bic.c
+++ b/net/ipv4/tcp_bic.c
@@ -30,8 +30,6 @@
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_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 @@
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 @@
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 @@
}
/* 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 @@
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 @@
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))