xref: /linux/net/ipv4/tcp_yeah.c (revision 4f2c0a4acffbec01079c28f839422e64ddeff004)
109c434b8SThomas Gleixner // SPDX-License-Identifier: GPL-2.0-only
25ef81475SAngelo P. Castellani /*
35ef81475SAngelo P. Castellani  *
45ef81475SAngelo P. Castellani  *   YeAH TCP
55ef81475SAngelo P. Castellani  *
65ef81475SAngelo P. Castellani  * For further details look at:
749564e55SWeilong Chen  *   https://web.archive.org/web/20080316215752/http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdf
85ef81475SAngelo P. Castellani  *
95ef81475SAngelo P. Castellani  */
107752237eSStephen Hemminger #include <linux/mm.h>
117752237eSStephen Hemminger #include <linux/module.h>
127752237eSStephen Hemminger #include <linux/skbuff.h>
137752237eSStephen Hemminger #include <linux/inet_diag.h>
145ef81475SAngelo P. Castellani 
157752237eSStephen Hemminger #include <net/tcp.h>
165ef81475SAngelo P. Castellani 
177752237eSStephen Hemminger #include "tcp_vegas.h"
185ef81475SAngelo P. Castellani 
1949564e55SWeilong Chen #define TCP_YEAH_ALPHA       80 /* number of packets queued at the bottleneck */
2049564e55SWeilong Chen #define TCP_YEAH_GAMMA        1 /* fraction of queue to be removed per rtt */
2149564e55SWeilong Chen #define TCP_YEAH_DELTA        3 /* log minimum fraction of cwnd to be removed on loss */
2249564e55SWeilong Chen #define TCP_YEAH_EPSILON      1 /* log maximum fraction to be removed on early decongestion */
2349564e55SWeilong Chen #define TCP_YEAH_PHY          8 /* maximum delta from base */
2449564e55SWeilong Chen #define TCP_YEAH_RHO         16 /* minimum number of consecutive rtt to consider competition on loss */
2549564e55SWeilong Chen #define TCP_YEAH_ZETA        50 /* minimum number of state switches to reset reno_count */
265ef81475SAngelo P. Castellani 
275ef81475SAngelo P. Castellani #define TCP_SCALABLE_AI_CNT	 100U
285ef81475SAngelo P. Castellani 
295ef81475SAngelo P. Castellani /* YeAH variables */
305ef81475SAngelo P. Castellani struct yeah {
317752237eSStephen Hemminger 	struct vegas vegas;	/* must be first */
325ef81475SAngelo P. Castellani 
335ef81475SAngelo P. Castellani 	/* YeAH */
345ef81475SAngelo P. Castellani 	u32 lastQ;
355ef81475SAngelo P. Castellani 	u32 doing_reno_now;
365ef81475SAngelo P. Castellani 
375ef81475SAngelo P. Castellani 	u32 reno_count;
385ef81475SAngelo P. Castellani 	u32 fast_count;
395ef81475SAngelo P. Castellani };
405ef81475SAngelo P. Castellani 
tcp_yeah_init(struct sock * sk)415ef81475SAngelo P. Castellani static void tcp_yeah_init(struct sock *sk)
425ef81475SAngelo P. Castellani {
435ef81475SAngelo P. Castellani 	struct tcp_sock *tp = tcp_sk(sk);
445ef81475SAngelo P. Castellani 	struct yeah *yeah = inet_csk_ca(sk);
455ef81475SAngelo P. Castellani 
465ef81475SAngelo P. Castellani 	tcp_vegas_init(sk);
475ef81475SAngelo P. Castellani 
485ef81475SAngelo P. Castellani 	yeah->doing_reno_now = 0;
495ef81475SAngelo P. Castellani 	yeah->lastQ = 0;
505ef81475SAngelo P. Castellani 
515ef81475SAngelo P. Castellani 	yeah->reno_count = 2;
525ef81475SAngelo P. Castellani 
535ef81475SAngelo P. Castellani 	/* Ensure the MD arithmetic works.  This is somewhat pedantic,
545ef81475SAngelo P. Castellani 	 * since I don't think we will see a cwnd this large. :) */
555ef81475SAngelo P. Castellani 	tp->snd_cwnd_clamp = min_t(u32, tp->snd_cwnd_clamp, 0xffffffff/128);
565ef81475SAngelo P. Castellani }
575ef81475SAngelo P. Castellani 
tcp_yeah_cong_avoid(struct sock * sk,u32 ack,u32 acked)5824901551SEric Dumazet static void tcp_yeah_cong_avoid(struct sock *sk, u32 ack, u32 acked)
595ef81475SAngelo P. Castellani {
605ef81475SAngelo P. Castellani 	struct tcp_sock *tp = tcp_sk(sk);
615ef81475SAngelo P. Castellani 	struct yeah *yeah = inet_csk_ca(sk);
625ef81475SAngelo P. Castellani 
6324901551SEric Dumazet 	if (!tcp_is_cwnd_limited(sk))
645ef81475SAngelo P. Castellani 		return;
655ef81475SAngelo P. Castellani 
66fa4cb9ebSPengcheng Yang 	if (tcp_in_slow_start(tp)) {
67fa4cb9ebSPengcheng Yang 		acked = tcp_slow_start(tp, acked);
68fa4cb9ebSPengcheng Yang 		if (!acked)
69fa4cb9ebSPengcheng Yang 			goto do_vegas;
705ef81475SAngelo P. Castellani 	}
715ef81475SAngelo P. Castellani 
72fa4cb9ebSPengcheng Yang 	if (!yeah->doing_reno_now) {
73fa4cb9ebSPengcheng Yang 		/* Scalable */
74*40570375SEric Dumazet 		tcp_cong_avoid_ai(tp, min(tcp_snd_cwnd(tp), TCP_SCALABLE_AI_CNT),
75fa4cb9ebSPengcheng Yang 				  acked);
765ef81475SAngelo P. Castellani 	} else {
775ef81475SAngelo P. Castellani 		/* Reno */
78*40570375SEric Dumazet 		tcp_cong_avoid_ai(tp, tcp_snd_cwnd(tp), acked);
795ef81475SAngelo P. Castellani 	}
805ef81475SAngelo P. Castellani 
817752237eSStephen Hemminger 	/* The key players are v_vegas.beg_snd_una and v_beg_snd_nxt.
825ef81475SAngelo P. Castellani 	 *
835ef81475SAngelo P. Castellani 	 * These are so named because they represent the approximate values
845ef81475SAngelo P. Castellani 	 * of snd_una and snd_nxt at the beginning of the current RTT. More
855ef81475SAngelo P. Castellani 	 * precisely, they represent the amount of data sent during the RTT.
865ef81475SAngelo P. Castellani 	 * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
877752237eSStephen Hemminger 	 * we will calculate that (v_beg_snd_nxt - v_vegas.beg_snd_una) outstanding
885ef81475SAngelo P. Castellani 	 * bytes of data have been ACKed during the course of the RTT, giving
895ef81475SAngelo P. Castellani 	 * an "actual" rate of:
905ef81475SAngelo P. Castellani 	 *
917752237eSStephen Hemminger 	 *     (v_beg_snd_nxt - v_vegas.beg_snd_una) / (rtt duration)
925ef81475SAngelo P. Castellani 	 *
937752237eSStephen Hemminger 	 * Unfortunately, v_vegas.beg_snd_una is not exactly equal to snd_una,
945ef81475SAngelo P. Castellani 	 * because delayed ACKs can cover more than one segment, so they
955ef81475SAngelo P. Castellani 	 * don't line up yeahly with the boundaries of RTTs.
965ef81475SAngelo P. Castellani 	 *
975ef81475SAngelo P. Castellani 	 * Another unfortunate fact of life is that delayed ACKs delay the
985ef81475SAngelo P. Castellani 	 * advance of the left edge of our send window, so that the number
995ef81475SAngelo P. Castellani 	 * of bytes we send in an RTT is often less than our cwnd will allow.
1005ef81475SAngelo P. Castellani 	 * So we keep track of our cwnd separately, in v_beg_snd_cwnd.
1015ef81475SAngelo P. Castellani 	 */
102fa4cb9ebSPengcheng Yang do_vegas:
1037752237eSStephen Hemminger 	if (after(ack, yeah->vegas.beg_snd_nxt)) {
1045ef81475SAngelo P. Castellani 		/* We do the Vegas calculations only if we got enough RTT
1055ef81475SAngelo P. Castellani 		 * samples that we can be reasonably sure that we got
1065ef81475SAngelo P. Castellani 		 * at least one RTT sample that wasn't from a delayed ACK.
1075ef81475SAngelo P. Castellani 		 * If we only had 2 samples total,
1085ef81475SAngelo P. Castellani 		 * then that means we're getting only 1 ACK per RTT, which
1095ef81475SAngelo P. Castellani 		 * means they're almost certainly delayed ACKs.
1105ef81475SAngelo P. Castellani 		 * If  we have 3 samples, we should be OK.
1115ef81475SAngelo P. Castellani 		 */
1125ef81475SAngelo P. Castellani 
1137752237eSStephen Hemminger 		if (yeah->vegas.cntRTT > 2) {
11443e68392SStephen Hemminger 			u32 rtt, queue;
11543e68392SStephen Hemminger 			u64 bw;
1165ef81475SAngelo P. Castellani 
1175ef81475SAngelo P. Castellani 			/* We have enough RTT samples, so, using the Vegas
1185ef81475SAngelo P. Castellani 			 * algorithm, we determine if we should increase or
1195ef81475SAngelo P. Castellani 			 * decrease cwnd, and by how much.
1205ef81475SAngelo P. Castellani 			 */
1215ef81475SAngelo P. Castellani 
1225ef81475SAngelo P. Castellani 			/* Pluck out the RTT we are using for the Vegas
1235ef81475SAngelo P. Castellani 			 * calculations. This is the min RTT seen during the
1245ef81475SAngelo P. Castellani 			 * last RTT. Taking the min filters out the effects
1255ef81475SAngelo P. Castellani 			 * of delayed ACKs, at the cost of noticing congestion
1265ef81475SAngelo P. Castellani 			 * a bit later.
1275ef81475SAngelo P. Castellani 			 */
1287752237eSStephen Hemminger 			rtt = yeah->vegas.minRTT;
1295ef81475SAngelo P. Castellani 
13043e68392SStephen Hemminger 			/* Compute excess number of packets above bandwidth
13143e68392SStephen Hemminger 			 * Avoid doing full 64 bit divide.
13243e68392SStephen Hemminger 			 */
133*40570375SEric Dumazet 			bw = tcp_snd_cwnd(tp);
1347752237eSStephen Hemminger 			bw *= rtt - yeah->vegas.baseRTT;
13543e68392SStephen Hemminger 			do_div(bw, rtt);
13643e68392SStephen Hemminger 			queue = bw;
1375ef81475SAngelo P. Castellani 
13843e68392SStephen Hemminger 			if (queue > TCP_YEAH_ALPHA ||
1397752237eSStephen Hemminger 			    rtt - yeah->vegas.baseRTT > (yeah->vegas.baseRTT / TCP_YEAH_PHY)) {
1409d4fb27dSJoe Perches 				if (queue > TCP_YEAH_ALPHA &&
141*40570375SEric Dumazet 				    tcp_snd_cwnd(tp) > yeah->reno_count) {
1425ef81475SAngelo P. Castellani 					u32 reduction = min(queue / TCP_YEAH_GAMMA ,
143*40570375SEric Dumazet 							    tcp_snd_cwnd(tp) >> TCP_YEAH_EPSILON);
1445ef81475SAngelo P. Castellani 
145*40570375SEric Dumazet 					tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) - reduction);
1465ef81475SAngelo P. Castellani 
147*40570375SEric Dumazet 					tcp_snd_cwnd_set(tp, max(tcp_snd_cwnd(tp),
148*40570375SEric Dumazet 								 yeah->reno_count));
1495ef81475SAngelo P. Castellani 
150*40570375SEric Dumazet 					tp->snd_ssthresh = tcp_snd_cwnd(tp);
1515ef81475SAngelo P. Castellani 				}
1525ef81475SAngelo P. Castellani 
1535ef81475SAngelo P. Castellani 				if (yeah->reno_count <= 2)
154*40570375SEric Dumazet 					yeah->reno_count = max(tcp_snd_cwnd(tp)>>1, 2U);
1555ef81475SAngelo P. Castellani 				else
1565ef81475SAngelo P. Castellani 					yeah->reno_count++;
1575ef81475SAngelo P. Castellani 
15843e68392SStephen Hemminger 				yeah->doing_reno_now = min(yeah->doing_reno_now + 1,
15943e68392SStephen Hemminger 							   0xffffffU);
1605ef81475SAngelo P. Castellani 			} else {
1615ef81475SAngelo P. Castellani 				yeah->fast_count++;
1625ef81475SAngelo P. Castellani 
1635ef81475SAngelo P. Castellani 				if (yeah->fast_count > TCP_YEAH_ZETA) {
1645ef81475SAngelo P. Castellani 					yeah->reno_count = 2;
1655ef81475SAngelo P. Castellani 					yeah->fast_count = 0;
1665ef81475SAngelo P. Castellani 				}
1675ef81475SAngelo P. Castellani 
1685ef81475SAngelo P. Castellani 				yeah->doing_reno_now = 0;
1695ef81475SAngelo P. Castellani 			}
1705ef81475SAngelo P. Castellani 
1715ef81475SAngelo P. Castellani 			yeah->lastQ = queue;
1725ef81475SAngelo P. Castellani 		}
1735ef81475SAngelo P. Castellani 
1745ef81475SAngelo P. Castellani 		/* Save the extent of the current window so we can use this
1755ef81475SAngelo P. Castellani 		 * at the end of the next RTT.
1765ef81475SAngelo P. Castellani 		 */
1777752237eSStephen Hemminger 		yeah->vegas.beg_snd_una  = yeah->vegas.beg_snd_nxt;
1787752237eSStephen Hemminger 		yeah->vegas.beg_snd_nxt  = tp->snd_nxt;
179*40570375SEric Dumazet 		yeah->vegas.beg_snd_cwnd = tcp_snd_cwnd(tp);
1805ef81475SAngelo P. Castellani 
1815ef81475SAngelo P. Castellani 		/* Wipe the slate clean for the next RTT. */
1827752237eSStephen Hemminger 		yeah->vegas.cntRTT = 0;
1837752237eSStephen Hemminger 		yeah->vegas.minRTT = 0x7fffffff;
1845ef81475SAngelo P. Castellani 	}
1855ef81475SAngelo P. Castellani }
1865ef81475SAngelo P. Castellani 
tcp_yeah_ssthresh(struct sock * sk)187688d1945Sstephen hemminger static u32 tcp_yeah_ssthresh(struct sock *sk)
188688d1945Sstephen hemminger {
1895ef81475SAngelo P. Castellani 	const struct tcp_sock *tp = tcp_sk(sk);
1905ef81475SAngelo P. Castellani 	struct yeah *yeah = inet_csk_ca(sk);
1915ef81475SAngelo P. Castellani 	u32 reduction;
1925ef81475SAngelo P. Castellani 
1935ef81475SAngelo P. Castellani 	if (yeah->doing_reno_now < TCP_YEAH_RHO) {
1945ef81475SAngelo P. Castellani 		reduction = yeah->lastQ;
1955ef81475SAngelo P. Castellani 
196*40570375SEric Dumazet 		reduction = min(reduction, max(tcp_snd_cwnd(tp)>>1, 2U));
1975ef81475SAngelo P. Castellani 
198*40570375SEric Dumazet 		reduction = max(reduction, tcp_snd_cwnd(tp) >> TCP_YEAH_DELTA);
1995ef81475SAngelo P. Castellani 	} else
200*40570375SEric Dumazet 		reduction = max(tcp_snd_cwnd(tp)>>1, 2U);
2015ef81475SAngelo P. Castellani 
2025ef81475SAngelo P. Castellani 	yeah->fast_count = 0;
2035ef81475SAngelo P. Castellani 	yeah->reno_count = max(yeah->reno_count>>1, 2U);
2045ef81475SAngelo P. Castellani 
205*40570375SEric Dumazet 	return max_t(int, tcp_snd_cwnd(tp) - reduction, 2);
2065ef81475SAngelo P. Castellani }
2075ef81475SAngelo P. Castellani 
208a252bebeSStephen Hemminger static struct tcp_congestion_ops tcp_yeah __read_mostly = {
2095ef81475SAngelo P. Castellani 	.init		= tcp_yeah_init,
2105ef81475SAngelo P. Castellani 	.ssthresh	= tcp_yeah_ssthresh,
211f1722a1bSYuchung Cheng 	.undo_cwnd      = tcp_reno_undo_cwnd,
2125ef81475SAngelo P. Castellani 	.cong_avoid	= tcp_yeah_cong_avoid,
2135ef81475SAngelo P. Castellani 	.set_state	= tcp_vegas_state,
2145ef81475SAngelo P. Castellani 	.cwnd_event	= tcp_vegas_cwnd_event,
2155ef81475SAngelo P. Castellani 	.get_info	= tcp_vegas_get_info,
216fa4cb9ebSPengcheng Yang 	.pkts_acked	= tcp_vegas_pkts_acked,
2175ef81475SAngelo P. Castellani 
2185ef81475SAngelo P. Castellani 	.owner		= THIS_MODULE,
2195ef81475SAngelo P. Castellani 	.name		= "yeah",
2205ef81475SAngelo P. Castellani };
2215ef81475SAngelo P. Castellani 
tcp_yeah_register(void)2225ef81475SAngelo P. Castellani static int __init tcp_yeah_register(void)
2235ef81475SAngelo P. Castellani {
2246706721dSEric Dumazet 	BUILD_BUG_ON(sizeof(struct yeah) > ICSK_CA_PRIV_SIZE);
2255ef81475SAngelo P. Castellani 	tcp_register_congestion_control(&tcp_yeah);
2265ef81475SAngelo P. Castellani 	return 0;
2275ef81475SAngelo P. Castellani }
2285ef81475SAngelo P. Castellani 
tcp_yeah_unregister(void)2295ef81475SAngelo P. Castellani static void __exit tcp_yeah_unregister(void)
2305ef81475SAngelo P. Castellani {
2315ef81475SAngelo P. Castellani 	tcp_unregister_congestion_control(&tcp_yeah);
2325ef81475SAngelo P. Castellani }
2335ef81475SAngelo P. Castellani 
2345ef81475SAngelo P. Castellani module_init(tcp_yeah_register);
2355ef81475SAngelo P. Castellani module_exit(tcp_yeah_unregister);
2365ef81475SAngelo P. Castellani 
2375ef81475SAngelo P. Castellani MODULE_AUTHOR("Angelo P. Castellani");
2385ef81475SAngelo P. Castellani MODULE_LICENSE("GPL");
2395ef81475SAngelo P. Castellani MODULE_DESCRIPTION("YeAH TCP");
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