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[TCP] BIC: remove low utilization code.

Browse Source 
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>
This commit is contained in:
Stephen Hemminger 2005-12-13 23:13:00 -08:00 committed by David S. Miller
parent d28d1e0801
commit 018da8f44c
1 changed files with 1 additions and 80 deletions
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81
net/ipv4/tcp_bic.c
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@ -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))