From ae27e98a51526595837ab7498b23d6478a198960 Mon Sep 17 00:00:00 2001 From: Sangtae Ha Date: Wed, 29 Oct 2008 00:07:18 -0400 Subject: [PATCH] [TCP] CUBIC v2.3 Signed-off-by: Sangtae Ha Signed-off-by: David S. Miller --- net/ipv4/tcp_cubic.c | 120 +++++++++++++++++++++++++++++++++++++++---- 1 file changed, 109 insertions(+), 11 deletions(-) diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c index 4a1221e5e8ee..ee467ec40c4f 100644 --- a/net/ipv4/tcp_cubic.c +++ b/net/ipv4/tcp_cubic.c @@ -1,13 +1,23 @@ /* - * TCP CUBIC: Binary Increase Congestion control for TCP v2.2 + * TCP CUBIC: Binary Increase Congestion control for TCP v2.3 * Home page: * http://netsrv.csc.ncsu.edu/twiki/bin/view/Main/BIC * This is from the implementation of CUBIC TCP in - * Injong Rhee, Lisong Xu. - * "CUBIC: A New TCP-Friendly High-Speed TCP Variant - * in PFLDnet 2005 + * Sangtae Ha, Injong Rhee and Lisong Xu, + * "CUBIC: A New TCP-Friendly High-Speed TCP Variant" + * in ACM SIGOPS Operating System Review, July 2008. * Available from: - * http://netsrv.csc.ncsu.edu/export/cubic-paper.pdf + * http://netsrv.csc.ncsu.edu/export/cubic_a_new_tcp_2008.pdf + * + * CUBIC integrates a new slow start algorithm, called HyStart. + * The details of HyStart are presented in + * Sangtae Ha and Injong Rhee, + * "Taming the Elephants: New TCP Slow Start", NCSU TechReport 2008. + * Available from: + * http://netsrv.csc.ncsu.edu/export/hystart_techreport_2008.pdf + * + * All testing results are available from: + * http://netsrv.csc.ncsu.edu/wiki/index.php/TCP_Testing * * Unless CUBIC is enabled and congestion window is large * this behaves the same as the original Reno. @@ -23,12 +33,26 @@ */ #define BICTCP_HZ 10 /* BIC HZ 2^10 = 1024 */ +/* Two methods of hybrid slow start */ +#define HYSTART_ACK_TRAIN 0x1 +#define HYSTART_DELAY 0x2 + +/* Number of delay samples for detecting the increase of delay */ +#define HYSTART_MIN_SAMPLES 8 +#define HYSTART_DELAY_MIN (2U<<3) +#define HYSTART_DELAY_MAX (16U<<3) +#define HYSTART_DELAY_THRESH(x) clamp(x, HYSTART_DELAY_MIN, HYSTART_DELAY_MAX) + static int fast_convergence __read_mostly = 1; static int beta __read_mostly = 717; /* = 717/1024 (BICTCP_BETA_SCALE) */ static int initial_ssthresh __read_mostly; static int bic_scale __read_mostly = 41; static int tcp_friendliness __read_mostly = 1; +static int hystart __read_mostly = 1; +static int hystart_detect __read_mostly = HYSTART_ACK_TRAIN | HYSTART_DELAY; +static int hystart_low_window __read_mostly = 16; + static u32 cube_rtt_scale __read_mostly; static u32 beta_scale __read_mostly; static u64 cube_factor __read_mostly; @@ -44,6 +68,13 @@ module_param(bic_scale, int, 0444); MODULE_PARM_DESC(bic_scale, "scale (scaled by 1024) value for bic function (bic_scale/1024)"); module_param(tcp_friendliness, int, 0644); MODULE_PARM_DESC(tcp_friendliness, "turn on/off tcp friendliness"); +module_param(hystart, int, 0644); +MODULE_PARM_DESC(hystart, "turn on/off hybrid slow start algorithm"); +module_param(hystart_detect, int, 0644); +MODULE_PARM_DESC(hystart_detect, "hyrbrid slow start detection mechanisms" + " 1: packet-train 2: delay 3: both packet-train and delay"); +module_param(hystart_low_window, int, 0644); +MODULE_PARM_DESC(hystart_low_window, "lower bound cwnd for hybrid slow start"); /* BIC TCP Parameters */ struct bictcp { @@ -59,7 +90,13 @@ struct bictcp { u32 ack_cnt; /* number of acks */ u32 tcp_cwnd; /* estimated tcp cwnd */ #define ACK_RATIO_SHIFT 4 - u32 delayed_ack; /* estimate the ratio of Packets/ACKs << 4 */ + u16 delayed_ack; /* estimate the ratio of Packets/ACKs << 4 */ + u8 sample_cnt; /* number of samples to decide curr_rtt */ + u8 found; /* the exit point is found? */ + u32 round_start; /* beginning of each round */ + u32 end_seq; /* end_seq of the round */ + u32 last_jiffies; /* last time when the ACK spacing is close */ + u32 curr_rtt; /* the minimum rtt of current round */ }; static inline void bictcp_reset(struct bictcp *ca) @@ -76,12 +113,28 @@ static inline void bictcp_reset(struct bictcp *ca) ca->delayed_ack = 2 << ACK_RATIO_SHIFT; ca->ack_cnt = 0; ca->tcp_cwnd = 0; + ca->found = 0; +} + +static inline void bictcp_hystart_reset(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bictcp *ca = inet_csk_ca(sk); + + ca->round_start = ca->last_jiffies = jiffies; + ca->end_seq = tp->snd_nxt; + ca->curr_rtt = 0; + ca->sample_cnt = 0; } static void bictcp_init(struct sock *sk) { bictcp_reset(inet_csk_ca(sk)); - if (initial_ssthresh) + + if (hystart) + bictcp_hystart_reset(sk); + + if (!hystart && initial_ssthresh) tcp_sk(sk)->snd_ssthresh = initial_ssthresh; } @@ -235,9 +288,11 @@ static void bictcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) if (!tcp_is_cwnd_limited(sk, in_flight)) return; - if (tp->snd_cwnd <= tp->snd_ssthresh) + if (tp->snd_cwnd <= tp->snd_ssthresh) { + if (hystart && after(ack, ca->end_seq)) + bictcp_hystart_reset(sk); tcp_slow_start(tp); - else { + } else { bictcp_update(ca, tp->snd_cwnd); /* In dangerous area, increase slowly. @@ -281,8 +336,45 @@ static u32 bictcp_undo_cwnd(struct sock *sk) static void bictcp_state(struct sock *sk, u8 new_state) { - if (new_state == TCP_CA_Loss) + if (new_state == TCP_CA_Loss) { bictcp_reset(inet_csk_ca(sk)); + bictcp_hystart_reset(sk); + } +} + +static void hystart_update(struct sock *sk, u32 delay) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bictcp *ca = inet_csk_ca(sk); + + if (!(ca->found & hystart_detect)) { + u32 curr_jiffies = jiffies; + + /* first detection parameter - ack-train detection */ + if (curr_jiffies - ca->last_jiffies <= msecs_to_jiffies(2)) { + ca->last_jiffies = curr_jiffies; + if (curr_jiffies - ca->round_start >= ca->delay_min>>4) + ca->found |= HYSTART_ACK_TRAIN; + } + + /* obtain the minimum delay of more than sampling packets */ + if (ca->sample_cnt < HYSTART_MIN_SAMPLES) { + if (ca->curr_rtt == 0 || ca->curr_rtt > delay) + ca->curr_rtt = delay; + + ca->sample_cnt++; + } else { + if (ca->curr_rtt > ca->delay_min + + HYSTART_DELAY_THRESH(ca->delay_min>>4)) + ca->found |= HYSTART_DELAY; + } + /* + * Either one of two conditions are met, + * we exit from slow start immediately. + */ + if (ca->found & hystart_detect) + tp->snd_ssthresh = tp->snd_cwnd; + } } /* Track delayed acknowledgment ratio using sliding window @@ -291,6 +383,7 @@ static void bictcp_state(struct sock *sk, u8 new_state) static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt_us) { const struct inet_connection_sock *icsk = inet_csk(sk); + const struct tcp_sock *tp = tcp_sk(sk); struct bictcp *ca = inet_csk_ca(sk); u32 delay; @@ -314,6 +407,11 @@ static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt_us) /* first time call or link delay decreases */ if (ca->delay_min == 0 || ca->delay_min > delay) ca->delay_min = delay; + + /* hystart triggers when cwnd is larger than some threshold */ + if (hystart && tp->snd_cwnd <= tp->snd_ssthresh && + tp->snd_cwnd >= hystart_low_window) + hystart_update(sk, delay); } static struct tcp_congestion_ops cubictcp = { @@ -372,4 +470,4 @@ module_exit(cubictcp_unregister); MODULE_AUTHOR("Sangtae Ha, Stephen Hemminger"); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("CUBIC TCP"); -MODULE_VERSION("2.2"); +MODULE_VERSION("2.3");