--- /dev/null
+/*
+ * 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");
projects / powerpc.git / commitdiff