diff options
Diffstat (limited to 'net/ipv4/tcp_yeah.c')
| -rw-r--r-- | net/ipv4/tcp_yeah.c | 260 |
1 files changed, 260 insertions, 0 deletions
diff --git a/net/ipv4/tcp_yeah.c b/net/ipv4/tcp_yeah.c new file mode 100644 index 00000000..05c3b6f0 --- /dev/null +++ b/net/ipv4/tcp_yeah.c @@ -0,0 +1,260 @@ +/* + * + * YeAH TCP + * + * For further details look at: + * 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 //lin number of packets queued at the bottleneck +#define TCP_YEAH_GAMMA 1 //lin 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 //lin maximum delta from base +#define TCP_YEAH_RHO 16 //lin minimum number of consecutive rtt to consider competition on loss +#define TCP_YEAH_ZETA 50 //lin minimum number of state switchs 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 in_flight) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct yeah *yeah = inet_csk_ca(sk); + + if (!tcp_is_cwnd_limited(sk, in_flight)) + return; + + if (tp->snd_cwnd <= tp->snd_ssthresh) + tcp_slow_start(tp); + + 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); + } + + /* 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 = { + .flags = TCP_CONG_RTT_STAMP, + .init = tcp_yeah_init, + .ssthresh = tcp_yeah_ssthresh, + .cong_avoid = tcp_yeah_cong_avoid, + .min_cwnd = tcp_reno_min_cwnd, + .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"); |