Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=65d1b4a7e73fe0e1f5275ad7d2d3547981480886
Commit:     65d1b4a7e73fe0e1f5275ad7d2d3547981480886
Parent:     42431592e74a968d919a46baf0515a2ee6978dac
Author:     Stephen Hemminger <[EMAIL PROTECTED]>
AuthorDate: Mon Apr 23 22:24:32 2007 -0700
Committer:  David S. Miller <[EMAIL PROTECTED]>
CommitDate: Wed Apr 25 22:29:44 2007 -0700

    [TCP]: TCP Illinois update.
    
    This version more closely matches the paper, and fixes several
    math errors. The biggest difference is that it updates alpha/beta
    once per RTT
    
    Signed-off-by: Stephen Hemminger <[EMAIL PROTECTED]>
    Signed-off-by: David S. Miller <[EMAIL PROTECTED]>
---
 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 91a2a34..ae62986 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");
-
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