diff options
Diffstat (limited to 'net/ipv4/tcp_illinois.c')
| -rw-r--r-- | net/ipv4/tcp_illinois.c | 284 |
1 files changed, 284 insertions, 0 deletions
diff --git a/net/ipv4/tcp_illinois.c b/net/ipv4/tcp_illinois.c new file mode 100644 index 000000000000..91a2a34604cd --- /dev/null +++ b/net/ipv4/tcp_illinois.c @@ -0,0 +1,284 @@ +/* + * TCP Illinois congestion control. + * Home page: + * http://www.ews.uiuc.edu/~shaoliu/tcpillinois/index.html + * + * The algorithm is described in: + * "TCP-Illinois: A Loss and Delay-Based Congestion Control Algorithm + * for High-Speed Networks" + * http://www.ews.uiuc.edu/~shaoliu/papersandslides/liubassri06perf.pdf + * + * Implemented from description in paper and ns-2 simulation. + * Copyright (C) 2007 Stephen Hemminger <shemminger@linux-foundation.org> + */ + +#include <linux/module.h> +#include <linux/skbuff.h> +#include <linux/inet_diag.h> +#include <asm/div64.h> +#include <net/tcp.h> + +#define ALPHA_SHIFT 7 +#define ALPHA_SCALE (1u<<ALPHA_SHIFT) +#define ALPHA_MIN ((3*ALPHA_SCALE)/10) /* ~0.3 */ +#define ALPHA_MAX (10*ALPHA_SCALE) /* 10.0 */ +#define ALPHA_BASE ALPHA_SCALE /* 1.0 */ + +#define BETA_SHIFT 6 +#define BETA_SCALE (1u<<BETA_SHIFT) +#define BETA_MIN (BETA_SCALE/8) /* 0.8 */ +#define BETA_MAX (BETA_SCALE/2) +#define BETA_BASE BETA_MAX /* 0.5 */ + +#define THETA 5 + +static int win_thresh __read_mostly = 15; +module_param(win_thresh, int, 0644); +MODULE_PARM_DESC(win_thresh, "Window threshold for starting adaptive sizing"); + +#define MAX_RTT 0x7fffffff + +/* TCP Illinois Parameters */ +struct tcp_illinois { + u32 last_alpha; + u32 min_rtt; + u32 max_rtt; + u32 rtt_low; + u32 rtt_cnt; + u64 sum_rtt; +}; + +static void tcp_illinois_init(struct sock *sk) +{ + struct tcp_illinois *ca = inet_csk_ca(sk); + + ca->last_alpha = ALPHA_BASE; + ca->min_rtt = 0x7fffffff; +} + +/* + * Keep track of min, max and average RTT + */ +static void tcp_illinois_rtt_calc(struct sock *sk, u32 rtt) +{ + struct tcp_illinois *ca = inet_csk_ca(sk); + + if (rtt < ca->min_rtt) + ca->min_rtt = rtt; + if (rtt > ca->max_rtt) + ca->max_rtt = rtt; + + if (++ca->rtt_cnt == 1) + ca->sum_rtt = rtt; + else + ca->sum_rtt += rtt; +} + +/* max queuing delay */ +static inline u32 max_delay(const struct tcp_illinois *ca) +{ + return ca->max_rtt - ca->min_rtt; +} + +/* average queueing delay */ +static u32 avg_delay(struct tcp_illinois *ca) +{ + u64 avg_rtt = ca->sum_rtt; + + do_div(avg_rtt, ca->rtt_cnt); + + ca->sum_rtt = 0; + ca->rtt_cnt = 0; + + return avg_rtt - ca->min_rtt; +} + +/* + * Compute value of alpha used for additive increase. + * If small window then use 1.0, equivalent to Reno. + * + * For larger windows, adjust based on average delay. + * A. If average delay is at minimum (we are uncongested), + * then use large alpha (10.0) to increase faster. + * B. If average delay is at maximum (getting congested) + * then use small alpha (1.0) + * + * The result is a convex window growth curve. + */ +static u32 alpha(const struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct tcp_illinois *ca = inet_csk_ca(sk); + u32 dm = max_delay(ca); + u32 da = avg_delay(ca); + u32 d1, a; + + if (tp->snd_cwnd < win_thresh) + return ALPHA_BASE; /* same as Reno (1.0) */ + + d1 = dm / 100; + if (da <= d1) { + /* Don't let noise force agressive response */ + if (ca->rtt_low < THETA) { + ++ca->rtt_low; + return ca->last_alpha; + } else + return ALPHA_MAX; + } + + ca->rtt_low = 0; + + /* + * Based on: + * + * (dm - d1) amin amax + * k1 = ------------------- + * amax - amin + * + * (dm - d1) amin + * k2 = ---------------- - d1 + * amax - amin + * + * k1 + * alpha = ---------- + * k2 + da + */ + + dm -= d1; + da -= d1; + + a = (dm * ALPHA_MAX) / (dm - (da * (ALPHA_MAX - ALPHA_MIN)) / ALPHA_MIN); + ca->last_alpha = a; + return a; +} + +/* + * Increase window in response to successful acknowledgment. + */ +static void tcp_illinois_cong_avoid(struct sock *sk, u32 ack, u32 rtt, + u32 in_flight, int flag) +{ + struct tcp_sock *tp = tcp_sk(sk); + + /* RFC2861 only increase cwnd if fully utilized */ + if (!tcp_is_cwnd_limited(sk, in_flight)) + return; + + /* In slow start */ + if (tp->snd_cwnd <= tp->snd_ssthresh) + tcp_slow_start(tp); + + else { + /* additive increase cwnd += alpha / cwnd */ + if ((tp->snd_cwnd_cnt * alpha(sk)) >> ALPHA_SHIFT >= tp->snd_cwnd) { + if (tp->snd_cwnd < tp->snd_cwnd_clamp) + tp->snd_cwnd++; + tp->snd_cwnd_cnt = 0; + } else + tp->snd_cwnd_cnt++; + } +} + +/* + * Beta used for multiplicative decrease. + * For small window sizes returns same value as Reno (0.5) + * + * If delay is small (10% of max) then beta = 1/8 + * If delay is up to 80% of max then beta = 1/2 + * In between is a linear function + */ +static inline u32 beta(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct tcp_illinois *ca = inet_csk_ca(sk); + u32 dm = max_delay(ca); + u32 da = avg_delay(ca); + u32 d2, d3; + + if (tp->snd_cwnd < win_thresh) + return BETA_BASE; + + d2 = dm / 10; + if (da <= d2) + return BETA_MIN; + d3 = (8 * dm) / 10; + if (da >= d3 || d3 <= d2) + return BETA_MAX; + + /* + * Based on: + * + * bmin d3 - bmax d2 + * k3 = ------------------- + * d3 - d2 + * + * bmax - bmin + * k4 = ------------- + * d3 - d2 + * + * b = k3 + k4 da + */ + return (BETA_MIN * d3 - BETA_MAX * d2 + (BETA_MAX - BETA_MIN) * da) + / (d3 - d2); +} + +static u32 tcp_illinois_ssthresh(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + /* Multiplicative decrease */ + return max((tp->snd_cwnd * beta(sk)) >> BETA_SHIFT, 2U); +} + +/* Extract info for TCP socket info provided via netlink. + * We aren't really doing Vegas, but we can provide RTT info + */ +static void tcp_illinois_get_info(struct sock *sk, u32 ext, + struct sk_buff *skb) +{ + const struct tcp_illinois *ca = inet_csk_ca(sk); + + if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) { + struct tcpvegas_info info = { + .tcpv_enabled = 1, + .tcpv_rttcnt = ca->rtt_cnt, + .tcpv_minrtt = ca->min_rtt, + }; + u64 avg_rtt = ca->sum_rtt; + do_div(avg_rtt, ca->rtt_cnt); + info.tcpv_rtt = avg_rtt; + + nla_put(skb, INET_DIAG_VEGASINFO, sizeof(info), &info); + } +} + +static struct tcp_congestion_ops tcp_illinois = { + .init = tcp_illinois_init, + .ssthresh = tcp_illinois_ssthresh, + .min_cwnd = tcp_reno_min_cwnd, + .cong_avoid = tcp_illinois_cong_avoid, + .rtt_sample = tcp_illinois_rtt_calc, + .get_info = tcp_illinois_get_info, + + .owner = THIS_MODULE, + .name = "illinois", +}; + +static int __init tcp_illinois_register(void) +{ + BUILD_BUG_ON(sizeof(struct tcp_illinois) > ICSK_CA_PRIV_SIZE); + return tcp_register_congestion_control(&tcp_illinois); +} + +static void __exit tcp_illinois_unregister(void) +{ + tcp_unregister_congestion_control(&tcp_illinois); +} + +module_init(tcp_illinois_register); +module_exit(tcp_illinois_unregister); + +MODULE_AUTHOR("Stephen Hemminger, Shao Liu"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("TCP Illinois"); +MODULE_VERSION("0.3"); |