diff options
Diffstat (limited to 'net')
| -rw-r--r-- | net/ipv4/Kconfig | 21 | ||||
| -rw-r--r-- | net/ipv4/Makefile | 1 | ||||
| -rw-r--r-- | net/ipv4/tcp_bic.c | 331 |
3 files changed, 353 insertions, 0 deletions
diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig index 567b03b1c349..712ebacacb62 100644 --- a/net/ipv4/Kconfig +++ b/net/ipv4/Kconfig @@ -433,5 +433,26 @@ config IP_TCPDIAG config IP_TCPDIAG_IPV6 def_bool (IP_TCPDIAG=y && IPV6=y) || (IP_TCPDIAG=m && IPV6) +# TCP Reno is builtin (required as fallback) +menu "TCP congestion control" + depends on INET + +config TCP_CONG_BIC + tristate "Binary Increase Congestion (BIC) control" + depends on INET + default y + ---help--- + BIC-TCP is a sender-side only change that ensures a linear RTT + fairness under large windows while offering both scalability and + bounded TCP-friendliness. The protocol combines two schemes + called additive increase and binary search increase. When the + congestion window is large, additive increase with a large + increment ensures linear RTT fairness as well as good + scalability. Under small congestion windows, binary search + increase provides TCP friendliness. + See http://www.csc.ncsu.edu/faculty/rhee/export/bitcp/ + +endmenu + source "net/ipv4/ipvs/Kconfig" diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile index 89c0b4cb470e..1d1cac5ac06a 100644 --- a/net/ipv4/Makefile +++ b/net/ipv4/Makefile @@ -31,6 +31,7 @@ obj-$(CONFIG_NETFILTER) += netfilter/ obj-$(CONFIG_IP_VS) += ipvs/ obj-$(CONFIG_IP_TCPDIAG) += tcp_diag.o obj-$(CONFIG_IP_ROUTE_MULTIPATH_CACHED) += multipath.o +obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \ xfrm4_output.o diff --git a/net/ipv4/tcp_bic.c b/net/ipv4/tcp_bic.c new file mode 100644 index 000000000000..ec38d45d6649 --- /dev/null +++ b/net/ipv4/tcp_bic.c @@ -0,0 +1,331 @@ +/* + * Binary Increase Congestion control for TCP + * + * This is from the implementation of BICTCP in + * Lison-Xu, Kahaled Harfoush, and Injong Rhee. + * "Binary Increase Congestion Control for Fast, Long Distance + * Networks" in InfoComm 2004 + * Available from: + * http://www.csc.ncsu.edu/faculty/rhee/export/bitcp.pdf + * + * Unless BIC is enabled and congestion window is large + * this behaves the same as the original Reno. + */ + +#include <linux/config.h> +#include <linux/mm.h> +#include <linux/module.h> +#include <net/tcp.h> + + +#define BICTCP_BETA_SCALE 1024 /* Scale factor beta calculation + * max_cwnd = snd_cwnd * beta + */ +#define BICTCP_B 4 /* + * In binary search, + * go to point (max+min)/N + */ + +static int fast_convergence = 1; +static int max_increment = 32; +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; + +module_param(fast_convergence, int, 0644); +MODULE_PARM_DESC(fast_convergence, "turn on/off fast convergence"); +module_param(max_increment, int, 0644); +MODULE_PARM_DESC(max_increment, "Limit on increment allowed during binary search"); +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); +MODULE_PARM_DESC(smooth_part, "log(B/(B*Smin))/log(B/(B-1))+B, # of RTT from Wmax-B to Wmax"); + + +/* BIC TCP Parameters */ +struct bictcp { + u32 cnt; /* increase cwnd by 1 after ACKs */ + u32 last_max_cwnd; /* last maximum snd_cwnd */ + 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 */ +}; + +static inline void bictcp_reset(struct bictcp *ca) +{ + ca->cnt = 0; + ca->last_max_cwnd = 0; + 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; +} + +static void bictcp_init(struct tcp_sock *tp) +{ + bictcp_reset(tcp_ca(tp)); + if (initial_ssthresh) + tp->snd_ssthresh = initial_ssthresh; +} + +/* + * Compute congestion window to use. + */ +static inline void bictcp_update(struct bictcp *ca, u32 cwnd) +{ + if (ca->last_cwnd == cwnd && + (s32)(tcp_time_stamp - ca->last_time) <= HZ / 32) + return; + + ca->last_cwnd = cwnd; + ca->last_time = tcp_time_stamp; + + if (ca->epoch_start == 0) /* record the beginning of an epoch */ + ca->epoch_start = tcp_time_stamp; + + /* start off normal */ + if (cwnd <= low_window) { + ca->cnt = cwnd; + return; + } + + /* binary increase */ + if (cwnd < ca->last_max_cwnd) { + __u32 dist = (ca->last_max_cwnd - cwnd) + / BICTCP_B; + + if (dist > max_increment) + /* linear increase */ + ca->cnt = cwnd / max_increment; + else if (dist <= 1U) + /* binary search increase */ + ca->cnt = (cwnd * smooth_part) / BICTCP_B; + else + /* binary search increase */ + ca->cnt = cwnd / dist; + } else { + /* slow start AMD linear increase */ + if (cwnd < ca->last_max_cwnd + BICTCP_B) + /* slow start */ + ca->cnt = (cwnd * smooth_part) / BICTCP_B; + else if (cwnd < ca->last_max_cwnd + max_increment*(BICTCP_B-1)) + /* slow start */ + ca->cnt = (cwnd * (BICTCP_B-1)) + / cwnd-ca->last_max_cwnd; + else + /* linear increase */ + ca->cnt = cwnd / max_increment; + } + + /* if in slow start or link utilization is very low */ + if ( ca->loss_cwnd == 0 || + (cwnd > ca->loss_cwnd && ca->low_utilization)) { + if (ca->cnt > 20) /* increase cwnd 5% per RTT */ + ca->cnt = 20; + } + + ca->cnt = (ca->cnt << ACK_RATIO_SHIFT) / ca->delayed_ack; + if (ca->cnt == 0) /* cannot be zero */ + ca->cnt = 1; +} + + +/* Detect low utilization in congestion avoidance */ +static inline void bictcp_low_utilization(struct tcp_sock *tp, int flag) +{ + struct bictcp *ca = tcp_ca(tp); + 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 tcp_sock *tp, u32 ack, + u32 seq_rtt, u32 in_flight, int data_acked) +{ + struct bictcp *ca = tcp_ca(tp); + + bictcp_low_utilization(tp, data_acked); + + if (in_flight < tp->snd_cwnd) + return; + + if (tp->snd_cwnd <= tp->snd_ssthresh) { + /* In "safe" area, increase. */ + if (tp->snd_cwnd < tp->snd_cwnd_clamp) + tp->snd_cwnd++; + } else { + bictcp_update(ca, tp->snd_cwnd); + + /* In dangerous area, increase slowly. + * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd + */ + if (tp->snd_cwnd_cnt >= ca->cnt) { + if (tp->snd_cwnd < tp->snd_cwnd_clamp) + tp->snd_cwnd++; + tp->snd_cwnd_cnt = 0; + } else + tp->snd_cwnd_cnt++; + } + +} + +/* + * behave like Reno until low_window is reached, + * then increase congestion window slowly + */ +static u32 bictcp_recalc_ssthresh(struct tcp_sock *tp) +{ + struct bictcp *ca = tcp_ca(tp); + + 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)) + / (2 * BICTCP_BETA_SCALE); + else + ca->last_max_cwnd = tp->snd_cwnd; + + ca->loss_cwnd = tp->snd_cwnd; + + + if (tp->snd_cwnd <= low_window) + return max(tp->snd_cwnd >> 1U, 2U); + else + return max((tp->snd_cwnd * beta) / BICTCP_BETA_SCALE, 2U); +} + +static u32 bictcp_undo_cwnd(struct tcp_sock *tp) +{ + struct bictcp *ca = tcp_ca(tp); + + return max(tp->snd_cwnd, ca->last_max_cwnd); +} + +static u32 bictcp_min_cwnd(struct tcp_sock *tp) +{ + return tp->snd_ssthresh; +} + +static void bictcp_state(struct tcp_sock *tp, u8 new_state) +{ + if (new_state == TCP_CA_Loss) + bictcp_reset(tcp_ca(tp)); +} + +/* Track delayed acknowledgement ratio using sliding window + * ratio = (15*ratio + sample) / 16 + */ +static void bictcp_acked(struct tcp_sock *tp, u32 cnt) +{ + if (cnt > 0 && tp->ca_state == TCP_CA_Open) { + struct bictcp *ca = tcp_ca(tp); + cnt -= ca->delayed_ack >> ACK_RATIO_SHIFT; + ca->delayed_ack += cnt; + } +} + + +static struct tcp_congestion_ops bictcp = { + .init = bictcp_init, + .ssthresh = bictcp_recalc_ssthresh, + .cong_avoid = bictcp_cong_avoid, + .set_state = bictcp_state, + .undo_cwnd = bictcp_undo_cwnd, + .min_cwnd = bictcp_min_cwnd, + .pkts_acked = bictcp_acked, + .owner = THIS_MODULE, + .name = "bic", +}; + +static int __init bictcp_register(void) +{ + BUG_ON(sizeof(struct bictcp) > TCP_CA_PRIV_SIZE); + return tcp_register_congestion_control(&bictcp); +} + +static void __exit bictcp_unregister(void) +{ + tcp_unregister_congestion_control(&bictcp); +} + +module_init(bictcp_register); +module_exit(bictcp_unregister); + +MODULE_AUTHOR("Stephen Hemminger"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("BIC TCP"); |