--- /dev/null
+/*
+ *
+ * YeAH TCP
+ *
+ * For further details look at:
+ * https://web.archive.org/web/20080316215752/http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdf
+ *
+ */
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/inet_diag.h>
+
+#include <net/tcp.h>
+
+#include "tcp_vegas.h"
+
+#define TCP_YEAH_ALPHA 80 /* number of packets queued at the bottleneck */
+#define TCP_YEAH_GAMMA 1 /* fraction of queue to be removed per rtt */
+#define TCP_YEAH_DELTA 3 /* log minimum fraction of cwnd to be removed on loss */
+#define TCP_YEAH_EPSILON 1 /* log maximum fraction to be removed on early decongestion */
+#define TCP_YEAH_PHY 8 /* maximum delta from base */
+#define TCP_YEAH_RHO 16 /* minimum number of consecutive rtt to consider competition on loss */
+#define TCP_YEAH_ZETA 50 /* minimum number of state switches to reset reno_count */
+
+#define TCP_SCALABLE_AI_CNT 100U
+
+/* YeAH variables */
+struct yeah {
+ struct vegas vegas; /* must be first */
+
+ /* YeAH */
+ u32 lastQ;
+ u32 doing_reno_now;
+
+ u32 reno_count;
+ u32 fast_count;
+
+ u32 pkts_acked;
+};
+
+static void tcp_yeah_init(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct yeah *yeah = inet_csk_ca(sk);
+
+ tcp_vegas_init(sk);
+
+ yeah->doing_reno_now = 0;
+ yeah->lastQ = 0;
+
+ yeah->reno_count = 2;
+
+ /* Ensure the MD arithmetic works. This is somewhat pedantic,
+ * since I don't think we will see a cwnd this large. :) */
+ tp->snd_cwnd_clamp = min_t(u32, tp->snd_cwnd_clamp, 0xffffffff/128);
+}
+
+static void tcp_yeah_pkts_acked(struct sock *sk, u32 pkts_acked, s32 rtt_us)
+{
+ const struct inet_connection_sock *icsk = inet_csk(sk);
+ struct yeah *yeah = inet_csk_ca(sk);
+
+ if (icsk->icsk_ca_state == TCP_CA_Open)
+ yeah->pkts_acked = pkts_acked;
+
+ tcp_vegas_pkts_acked(sk, pkts_acked, rtt_us);
+}
+
+static void tcp_yeah_cong_avoid(struct sock *sk, u32 ack, u32 acked)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct yeah *yeah = inet_csk_ca(sk);
+
+ if (!tcp_is_cwnd_limited(sk))
+ return;
+
+ if (tp->snd_cwnd <= tp->snd_ssthresh)
+ tcp_slow_start(tp, acked);
+
+ else if (!yeah->doing_reno_now) {
+ /* Scalable */
+
+ tp->snd_cwnd_cnt += yeah->pkts_acked;
+ if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)) {
+ if (tp->snd_cwnd < tp->snd_cwnd_clamp)
+ tp->snd_cwnd++;
+ tp->snd_cwnd_cnt = 0;
+ }
+
+ yeah->pkts_acked = 1;
+
+ } else {
+ /* Reno */
+ tcp_cong_avoid_ai(tp, tp->snd_cwnd, 1);
+ }
+
+ /* The key players are v_vegas.beg_snd_una and v_beg_snd_nxt.
+ *
+ * These are so named because they represent the approximate values
+ * of snd_una and snd_nxt at the beginning of the current RTT. More
+ * precisely, they represent the amount of data sent during the RTT.
+ * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
+ * we will calculate that (v_beg_snd_nxt - v_vegas.beg_snd_una) outstanding
+ * bytes of data have been ACKed during the course of the RTT, giving
+ * an "actual" rate of:
+ *
+ * (v_beg_snd_nxt - v_vegas.beg_snd_una) / (rtt duration)
+ *
+ * Unfortunately, v_vegas.beg_snd_una is not exactly equal to snd_una,
+ * because delayed ACKs can cover more than one segment, so they
+ * don't line up yeahly with the boundaries of RTTs.
+ *
+ * Another unfortunate fact of life is that delayed ACKs delay the
+ * advance of the left edge of our send window, so that the number
+ * of bytes we send in an RTT is often less than our cwnd will allow.
+ * So we keep track of our cwnd separately, in v_beg_snd_cwnd.
+ */
+
+ if (after(ack, yeah->vegas.beg_snd_nxt)) {
+ /* We do the Vegas calculations only if we got enough RTT
+ * samples that we can be reasonably sure that we got
+ * at least one RTT sample that wasn't from a delayed ACK.
+ * If we only had 2 samples total,
+ * then that means we're getting only 1 ACK per RTT, which
+ * means they're almost certainly delayed ACKs.
+ * If we have 3 samples, we should be OK.
+ */
+
+ if (yeah->vegas.cntRTT > 2) {
+ u32 rtt, queue;
+ u64 bw;
+
+ /* We have enough RTT samples, so, using the Vegas
+ * algorithm, we determine if we should increase or
+ * decrease cwnd, and by how much.
+ */
+
+ /* Pluck out the RTT we are using for the Vegas
+ * calculations. This is the min RTT seen during the
+ * last RTT. Taking the min filters out the effects
+ * of delayed ACKs, at the cost of noticing congestion
+ * a bit later.
+ */
+ rtt = yeah->vegas.minRTT;
+
+ /* Compute excess number of packets above bandwidth
+ * Avoid doing full 64 bit divide.
+ */
+ bw = tp->snd_cwnd;
+ bw *= rtt - yeah->vegas.baseRTT;
+ do_div(bw, rtt);
+ queue = bw;
+
+ if (queue > TCP_YEAH_ALPHA ||
+ rtt - yeah->vegas.baseRTT > (yeah->vegas.baseRTT / TCP_YEAH_PHY)) {
+ if (queue > TCP_YEAH_ALPHA &&
+ tp->snd_cwnd > yeah->reno_count) {
+ u32 reduction = min(queue / TCP_YEAH_GAMMA ,
+ tp->snd_cwnd >> TCP_YEAH_EPSILON);
+
+ tp->snd_cwnd -= reduction;
+
+ tp->snd_cwnd = max(tp->snd_cwnd,
+ yeah->reno_count);
+
+ tp->snd_ssthresh = tp->snd_cwnd;
+ }
+
+ if (yeah->reno_count <= 2)
+ yeah->reno_count = max(tp->snd_cwnd>>1, 2U);
+ else
+ yeah->reno_count++;
+
+ yeah->doing_reno_now = min(yeah->doing_reno_now + 1,
+ 0xffffffU);
+ } else {
+ yeah->fast_count++;
+
+ if (yeah->fast_count > TCP_YEAH_ZETA) {
+ yeah->reno_count = 2;
+ yeah->fast_count = 0;
+ }
+
+ yeah->doing_reno_now = 0;
+ }
+
+ yeah->lastQ = queue;
+ }
+
+ /* Save the extent of the current window so we can use this
+ * at the end of the next RTT.
+ */
+ yeah->vegas.beg_snd_una = yeah->vegas.beg_snd_nxt;
+ yeah->vegas.beg_snd_nxt = tp->snd_nxt;
+ yeah->vegas.beg_snd_cwnd = tp->snd_cwnd;
+
+ /* Wipe the slate clean for the next RTT. */
+ yeah->vegas.cntRTT = 0;
+ yeah->vegas.minRTT = 0x7fffffff;
+ }
+}
+
+static u32 tcp_yeah_ssthresh(struct sock *sk)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+ struct yeah *yeah = inet_csk_ca(sk);
+ u32 reduction;
+
+ if (yeah->doing_reno_now < TCP_YEAH_RHO) {
+ reduction = yeah->lastQ;
+
+ reduction = min(reduction, max(tp->snd_cwnd>>1, 2U));
+
+ reduction = max(reduction, tp->snd_cwnd >> TCP_YEAH_DELTA);
+ } else
+ reduction = max(tp->snd_cwnd>>1, 2U);
+
+ yeah->fast_count = 0;
+ yeah->reno_count = max(yeah->reno_count>>1, 2U);
+
+ return tp->snd_cwnd - reduction;
+}
+
+static struct tcp_congestion_ops tcp_yeah __read_mostly = {
+ .init = tcp_yeah_init,
+ .ssthresh = tcp_yeah_ssthresh,
+ .cong_avoid = tcp_yeah_cong_avoid,
+ .set_state = tcp_vegas_state,
+ .cwnd_event = tcp_vegas_cwnd_event,
+ .get_info = tcp_vegas_get_info,
+ .pkts_acked = tcp_yeah_pkts_acked,
+
+ .owner = THIS_MODULE,
+ .name = "yeah",
+};
+
+static int __init tcp_yeah_register(void)
+{
+ BUG_ON(sizeof(struct yeah) > ICSK_CA_PRIV_SIZE);
+ tcp_register_congestion_control(&tcp_yeah);
+ return 0;
+}
+
+static void __exit tcp_yeah_unregister(void)
+{
+ tcp_unregister_congestion_control(&tcp_yeah);
+}
+
+module_init(tcp_yeah_register);
+module_exit(tcp_yeah_unregister);
+
+MODULE_AUTHOR("Angelo P. Castellani");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("YeAH TCP");
Code Review / kvmfornfv.git / blobdiff