diff options
Diffstat (limited to 'net/ipv4/tcp_illinois.c')
-rw-r--r-- | net/ipv4/tcp_illinois.c | 356 |
1 files changed, 356 insertions, 0 deletions
diff --git a/net/ipv4/tcp_illinois.c b/net/ipv4/tcp_illinois.c new file mode 100644 index 000000000000..4adc47c55351 --- /dev/null +++ b/net/ipv4/tcp_illinois.c @@ -0,0 +1,356 @@ +/* + * 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 U32_MAX ((u32)~0U) +#define RTT_MAX (U32_MAX / ALPHA_MAX) /* 3.3 secs */ + +#define BETA_SHIFT 6 +#define BETA_SCALE (1u<<BETA_SHIFT) +#define BETA_MIN (BETA_SCALE/8) /* 0.125 */ +#define BETA_MAX (BETA_SCALE/2) /* 0.5 */ +#define BETA_BASE BETA_MAX + +static int win_thresh __read_mostly = 15; +module_param(win_thresh, int, 0); +MODULE_PARM_DESC(win_thresh, "Window threshold for starting adaptive sizing"); + +static int theta __read_mostly = 5; +module_param(theta, int, 0); +MODULE_PARM_DESC(theta, "# of fast RTT's before full growth"); + +/* TCP Illinois Parameters */ +struct illinois { + u64 sum_rtt; /* sum of rtt's measured within last rtt */ + u16 cnt_rtt; /* # of rtts measured within last rtt */ + u32 base_rtt; /* min of all rtt in usec */ + u32 max_rtt; /* max of all rtt in usec */ + u32 end_seq; /* right edge of current RTT */ + u32 alpha; /* Additive increase */ + u32 beta; /* Muliplicative decrease */ + u16 acked; /* # packets acked by current ACK */ + u8 rtt_above; /* average rtt has gone above threshold */ + u8 rtt_low; /* # of rtts measurements below threshold */ +}; + +static void rtt_reset(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct illinois *ca = inet_csk_ca(sk); + + ca->end_seq = tp->snd_nxt; + ca->cnt_rtt = 0; + ca->sum_rtt = 0; + + /* TODO: age max_rtt? */ +} + +static void tcp_illinois_init(struct sock *sk) +{ + struct illinois *ca = inet_csk_ca(sk); + + ca->alpha = ALPHA_MAX; + ca->beta = BETA_BASE; + ca->base_rtt = 0x7fffffff; + ca->max_rtt = 0; + + ca->acked = 0; + ca->rtt_low = 0; + ca->rtt_above = 0; + + rtt_reset(sk); +} + +/* Measure RTT for each ack. */ +static void tcp_illinois_acked(struct sock *sk, u32 pkts_acked, ktime_t last) +{ + struct illinois *ca = inet_csk_ca(sk); + u32 rtt; + + ca->acked = pkts_acked; + + rtt = ktime_to_us(net_timedelta(last)); + + /* ignore bogus values, this prevents wraparound in alpha math */ + if (rtt > RTT_MAX) + rtt = RTT_MAX; + + /* keep track of minimum RTT seen so far */ + if (ca->base_rtt > rtt) + ca->base_rtt = rtt; + + /* and max */ + if (ca->max_rtt < rtt) + ca->max_rtt = rtt; + + ++ca->cnt_rtt; + ca->sum_rtt += rtt; +} + +/* Maximum queuing delay */ +static inline u32 max_delay(const struct illinois *ca) +{ + return ca->max_rtt - ca->base_rtt; +} + +/* Average queuing delay */ +static inline u32 avg_delay(const struct illinois *ca) +{ + u64 t = ca->sum_rtt; + + do_div(t, ca->cnt_rtt); + return t - ca->base_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 (0.3) + * + * The result is a convex window growth curve. + */ +static u32 alpha(struct illinois *ca, u32 da, u32 dm) +{ + u32 d1 = dm / 100; /* Low threshold */ + + if (da <= d1) { + /* If never got out of low delay zone, then use max */ + if (!ca->rtt_above) + return ALPHA_MAX; + + /* Wait for 5 good RTT's before allowing alpha to go alpha max. + * This prevents one good RTT from causing sudden window increase. + */ + if (++ca->rtt_low < theta) + return ca->alpha; + + ca->rtt_low = 0; + ca->rtt_above = 0; + return ALPHA_MAX; + } + + ca->rtt_above = 1; + + /* + * Based on: + * + * (dm - d1) amin amax + * k1 = ------------------- + * amax - amin + * + * (dm - d1) amin + * k2 = ---------------- - d1 + * amax - amin + * + * k1 + * alpha = ---------- + * k2 + da + */ + + dm -= d1; + da -= d1; + return (dm * ALPHA_MAX) / + (dm + (da * (ALPHA_MAX - ALPHA_MIN)) / ALPHA_MIN); +} + +/* + * 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 u32 beta(u32 da, u32 dm) +{ + u32 d2, d3; + + 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); +} + +/* Update alpha and beta values once per RTT */ +static void update_params(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct illinois *ca = inet_csk_ca(sk); + + if (tp->snd_cwnd < win_thresh) { + ca->alpha = ALPHA_BASE; + ca->beta = BETA_BASE; + } else if (ca->cnt_rtt > 0) { + u32 dm = max_delay(ca); + u32 da = avg_delay(ca); + + ca->alpha = alpha(ca, da, dm); + ca->beta = beta(da, dm); + } + + rtt_reset(sk); +} + +/* + * In case of loss, reset to default values + */ +static void tcp_illinois_state(struct sock *sk, u8 new_state) +{ + struct illinois *ca = inet_csk_ca(sk); + + if (new_state == TCP_CA_Loss) { + ca->alpha = ALPHA_BASE; + ca->beta = BETA_BASE; + ca->rtt_low = 0; + ca->rtt_above = 0; + rtt_reset(sk); + } +} + +/* + * 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); + struct illinois *ca = inet_csk_ca(sk); + + if (after(ack, ca->end_seq)) + update_params(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 { + u32 delta; + + /* snd_cwnd_cnt is # of packets since last cwnd increment */ + tp->snd_cwnd_cnt += ca->acked; + ca->acked = 1; + + /* This is close approximation of: + * tp->snd_cwnd += alpha/tp->snd_cwnd + */ + delta = (tp->snd_cwnd_cnt * ca->alpha) >> ALPHA_SHIFT; + if (delta >= tp->snd_cwnd) { + tp->snd_cwnd = min(tp->snd_cwnd + delta / tp->snd_cwnd, + (u32) tp->snd_cwnd_clamp); + tp->snd_cwnd_cnt = 0; + } + } +} + +static u32 tcp_illinois_ssthresh(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct illinois *ca = inet_csk_ca(sk); + + /* Multiplicative decrease */ + return max((tp->snd_cwnd * ca->beta) >> BETA_SHIFT, 2U); +} + + +/* Extract info for Tcp socket info provided via netlink. */ +static void tcp_illinois_info(struct sock *sk, u32 ext, + struct sk_buff *skb) +{ + const struct illinois *ca = inet_csk_ca(sk); + + if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) { + struct tcpvegas_info info = { + .tcpv_enabled = 1, + .tcpv_rttcnt = ca->cnt_rtt, + .tcpv_minrtt = ca->base_rtt, + }; + u64 t = ca->sum_rtt; + + do_div(t, ca->cnt_rtt); + info.tcpv_rtt = t; + + nla_put(skb, INET_DIAG_VEGASINFO, sizeof(info), &info); + } +} + +static struct tcp_congestion_ops tcp_illinois = { + .flags = TCP_CONG_RTT_STAMP, + .init = tcp_illinois_init, + .ssthresh = tcp_illinois_ssthresh, + .min_cwnd = tcp_reno_min_cwnd, + .cong_avoid = tcp_illinois_cong_avoid, + .set_state = tcp_illinois_state, + .get_info = tcp_illinois_info, + .pkts_acked = tcp_illinois_acked, + + .owner = THIS_MODULE, + .name = "illinois", +}; + +static int __init tcp_illinois_register(void) +{ + BUILD_BUG_ON(sizeof(struct 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("1.0"); |