diff options
| -rw-r--r-- | net/ipv4/tcp_illinois.c | 298 |
1 files changed, 186 insertions, 112 deletions
diff --git a/net/ipv4/tcp_illinois.c b/net/ipv4/tcp_illinois.c index 91a2a34604cd..ae6298600886 100644 --- a/net/ipv4/tcp_illinois.c +++ b/net/ipv4/tcp_illinois.c @@ -23,74 +23,106 @@ #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 U32_MAX ((u32)~0U) +#define RTT_MAX (U32_MAX / ALPHA_MAX) /* 3.3 secs */ #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 +#define BETA_MIN (BETA_SCALE/8) /* 0.125 */ +#define BETA_MAX (BETA_SCALE/2) /* 0.5 */ +#define BETA_BASE BETA_MAX static int win_thresh __read_mostly = 15; -module_param(win_thresh, int, 0644); +module_param(win_thresh, int, 0); MODULE_PARM_DESC(win_thresh, "Window threshold for starting adaptive sizing"); -#define MAX_RTT 0x7fffffff +static int theta __read_mostly = 5; +module_param(theta, int, 0); +MODULE_PARM_DESC(theta, "# of fast RTT's before full growth"); /* TCP Illinois Parameters */ -struct tcp_illinois { - u32 last_alpha; - u32 min_rtt; - u32 max_rtt; - u32 rtt_low; - u32 rtt_cnt; - u64 sum_rtt; +struct illinois { + u64 sum_rtt; /* sum of rtt's measured within last rtt */ + u16 cnt_rtt; /* # of rtts measured within last rtt */ + u32 base_rtt; /* min of all rtt in usec */ + u32 max_rtt; /* max of all rtt in usec */ + u32 end_seq; /* right edge of current RTT */ + u32 alpha; /* Additive increase */ + u32 beta; /* Muliplicative decrease */ + u16 acked; /* # packets acked by current ACK */ + u8 rtt_above; /* average rtt has gone above threshold */ + u8 rtt_low; /* # of rtts measurements below threshold */ }; +static void rtt_reset(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct illinois *ca = inet_csk_ca(sk); + + ca->end_seq = tp->snd_nxt; + ca->cnt_rtt = 0; + ca->sum_rtt = 0; + + /* TODO: age max_rtt? */ +} + static void tcp_illinois_init(struct sock *sk) { - struct tcp_illinois *ca = inet_csk_ca(sk); + struct illinois *ca = inet_csk_ca(sk); + + ca->alpha = ALPHA_MAX; + ca->beta = BETA_BASE; + ca->base_rtt = 0x7fffffff; + ca->max_rtt = 0; + + ca->acked = 0; + ca->rtt_low = 0; + ca->rtt_above = 0; - ca->last_alpha = ALPHA_BASE; - ca->min_rtt = 0x7fffffff; + rtt_reset(sk); } -/* - * Keep track of min, max and average RTT - */ -static void tcp_illinois_rtt_calc(struct sock *sk, u32 rtt) +/* Measure RTT for each ack. */ +static void tcp_illinois_rtt_sample(struct sock *sk, u32 rtt) { - struct tcp_illinois *ca = inet_csk_ca(sk); + struct illinois *ca = inet_csk_ca(sk); + + /* ignore bogus values, this prevents wraparound in alpha math */ + if (rtt > RTT_MAX) + rtt = RTT_MAX; - if (rtt < ca->min_rtt) - ca->min_rtt = rtt; - if (rtt > ca->max_rtt) + /* keep track of minimum RTT seen so far */ + if (ca->base_rtt > rtt) + ca->base_rtt = rtt; + + /* and max */ + if (ca->max_rtt < rtt) ca->max_rtt = rtt; - if (++ca->rtt_cnt == 1) - ca->sum_rtt = rtt; - else - ca->sum_rtt += rtt; + ++ca->cnt_rtt; + ca->sum_rtt += rtt; } -/* max queuing delay */ -static inline u32 max_delay(const struct tcp_illinois *ca) +/* Capture count of packets covered by ack, to adjust for delayed acks */ +static void tcp_illinois_acked(struct sock *sk, u32 pkts_acked) { - return ca->max_rtt - ca->min_rtt; + struct illinois *ca = inet_csk_ca(sk); + ca->acked = pkts_acked; } -/* average queueing delay */ -static u32 avg_delay(struct tcp_illinois *ca) +/* Maximum queuing delay */ +static inline u32 max_delay(const struct illinois *ca) { - u64 avg_rtt = ca->sum_rtt; - - do_div(avg_rtt, ca->rtt_cnt); + return ca->max_rtt - ca->base_rtt; +} - ca->sum_rtt = 0; - ca->rtt_cnt = 0; +/* Average queuing delay */ +static inline u32 avg_delay(const struct illinois *ca) +{ + u64 t = ca->sum_rtt; - return avg_rtt - ca->min_rtt; + do_div(t, ca->cnt_rtt); + return t - ca->base_rtt; } /* @@ -101,32 +133,31 @@ static u32 avg_delay(struct tcp_illinois *ca) * 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) + * then use small alpha (0.3) * * The result is a convex window growth curve. */ -static u32 alpha(const struct sock *sk) +static u32 alpha(struct illinois *ca, u32 da, u32 dm) { - 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; + u32 d1 = dm / 100; /* Low threshold */ - 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 + /* If never got out of low delay zone, then use max */ + if (!ca->rtt_above) return ALPHA_MAX; + + /* Wait for 5 good RTT's before allowing alpha to go alpha max. + * This prevents one good RTT from causing sudden window increase. + */ + if (++ca->rtt_low < theta) + return ca->alpha; + + ca->rtt_low = 0; + ca->rtt_above = 0; + return ALPHA_MAX; } - ca->rtt_low = 0; + ca->rtt_above = 1; /* * Based on: @@ -146,37 +177,8 @@ static u32 alpha(const struct sock *sk) 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++; - } + return (dm * ALPHA_MAX) / + (dm + (da * (ALPHA_MAX - ALPHA_MIN)) / ALPHA_MIN); } /* @@ -187,20 +189,14 @@ static void tcp_illinois_cong_avoid(struct sock *sk, u32 ack, u32 rtt, * 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) +static u32 beta(u32 da, u32 dm) { - 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; @@ -222,31 +218,107 @@ static inline u32 beta(struct sock *sk) / (d3 - d2); } +/* Update alpha and beta values once per RTT */ +static void update_params(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct illinois *ca = inet_csk_ca(sk); + + if (tp->snd_cwnd < win_thresh) { + ca->alpha = ALPHA_BASE; + ca->beta = BETA_BASE; + } else if (ca->cnt_rtt > 0) { + u32 dm = max_delay(ca); + u32 da = avg_delay(ca); + + ca->alpha = alpha(ca, da, dm); + ca->beta = beta(da, dm); + } + + rtt_reset(sk); +} + +/* + * In case of loss, reset to default values + */ +static void tcp_illinois_state(struct sock *sk, u8 new_state) +{ + struct illinois *ca = inet_csk_ca(sk); + + if (new_state == TCP_CA_Loss) { + ca->alpha = ALPHA_BASE; + ca->beta = BETA_BASE; + ca->rtt_low = 0; + ca->rtt_above = 0; + rtt_reset(sk); + } +} + +/* + * 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); + struct illinois *ca = inet_csk_ca(sk); + + if (after(ack, ca->end_seq)) + update_params(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 { + u32 delta; + + /* snd_cwnd_cnt is # of packets since last cwnd increment */ + tp->snd_cwnd_cnt += ca->acked; + ca->acked = 1; + + /* This is close approximation of: + * tp->snd_cwnd += alpha/tp->snd_cwnd + */ + delta = (tp->snd_cwnd_cnt * ca->alpha) >> ALPHA_SHIFT; + if (delta >= tp->snd_cwnd) { + tp->snd_cwnd = min(tp->snd_cwnd + delta / tp->snd_cwnd, + (u32) tp->snd_cwnd_clamp); + tp->snd_cwnd_cnt = 0; + } + } +} + static u32 tcp_illinois_ssthresh(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); + struct illinois *ca = inet_csk_ca(sk); /* Multiplicative decrease */ - return max((tp->snd_cwnd * beta(sk)) >> BETA_SHIFT, 2U); + return max((tp->snd_cwnd * ca->beta) >> 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) + +/* Extract info for Tcp socket info provided via netlink. */ +static void tcp_illinois_info(struct sock *sk, u32 ext, + struct sk_buff *skb) { - const struct tcp_illinois *ca = inet_csk_ca(sk); + const struct 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, + .tcpv_rttcnt = ca->cnt_rtt, + .tcpv_minrtt = ca->base_rtt, }; - u64 avg_rtt = ca->sum_rtt; - do_div(avg_rtt, ca->rtt_cnt); - info.tcpv_rtt = avg_rtt; + u64 t = ca->sum_rtt; + + do_div(t, ca->cnt_rtt); + info.tcpv_rtt = t; nla_put(skb, INET_DIAG_VEGASINFO, sizeof(info), &info); } @@ -257,8 +329,10 @@ static struct tcp_congestion_ops tcp_illinois = { .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, + .set_state = tcp_illinois_state, + .rtt_sample = tcp_illinois_rtt_sample, + .get_info = tcp_illinois_info, + .pkts_acked = tcp_illinois_acked, .owner = THIS_MODULE, .name = "illinois", @@ -266,7 +340,7 @@ static struct tcp_congestion_ops tcp_illinois = { static int __init tcp_illinois_register(void) { - BUILD_BUG_ON(sizeof(struct tcp_illinois) > ICSK_CA_PRIV_SIZE); + BUILD_BUG_ON(sizeof(struct illinois) > ICSK_CA_PRIV_SIZE); return tcp_register_congestion_control(&tcp_illinois); } @@ -281,4 +355,4 @@ module_exit(tcp_illinois_unregister); MODULE_AUTHOR("Stephen Hemminger, Shao Liu"); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("TCP Illinois"); -MODULE_VERSION("0.3"); +MODULE_VERSION("1.0"); |