net/ipv4/tcp_scalable.c

   1 /* Tom Kelly's Scalable TCP
   2  *
   3  * See http://www.deneholme.net/tom/scalable/
   4  *
   5  * John Heffner <jheffner@sc.edu>
   6  */
   7
   8 #include <linux/module.h>
   9 #include <net/tcp.h>
  10
  11 /* These factors derived from the recommended values in the aer:
  12  * .01 and and 7/8. We use 50 instead of 100 to account for
  13  * delayed ack.
  14  */
  15 #define TCP_SCALABLE_AI_CNT     50U
  16 #define TCP_SCALABLE_MD_SCALE   3
  17
  18 struct scalable {
  19         u32 loss_cwnd;
  20 };
  21
  22 static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
  23 {
  24         struct tcp_sock *tp = tcp_sk(sk);
  25
  26         if (!tcp_is_cwnd_limited(sk))
  27                 return;
  28
  29         if (tcp_in_slow_start(tp))
  30                 tcp_slow_start(tp, acked);
  31         else
  32                 tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
  33                                   1);
  34 }
  35
  36 static u32 tcp_scalable_ssthresh(struct sock *sk)
  37 {
  38         const struct tcp_sock *tp = tcp_sk(sk);
  39         struct scalable *ca = inet_csk_ca(sk);
  40
  41         ca->loss_cwnd = tp->snd_cwnd;
  42
  43         return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
  44 }
  45
  46 static u32 tcp_scalable_cwnd_undo(struct sock *sk)
  47 {
  48         const struct scalable *ca = inet_csk_ca(sk);
  49
  50         return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
  51 }
  52
  53 static struct tcp_congestion_ops tcp_scalable __read_mostly = {
  54         .ssthresh       = tcp_scalable_ssthresh,
  55         .undo_cwnd      = tcp_scalable_cwnd_undo,
  56         .cong_avoid     = tcp_scalable_cong_avoid,
  57
  58         .owner          = THIS_MODULE,
  59         .name           = "scalable",
  60 };
  61
  62 static int __init tcp_scalable_register(void)
  63 {
  64         return tcp_register_congestion_control(&tcp_scalable);
  65 }
  66
  67 static void __exit tcp_scalable_unregister(void)
  68 {
  69         tcp_unregister_congestion_control(&tcp_scalable);
  70 }
  71
  72 module_init(tcp_scalable_register);
  73 module_exit(tcp_scalable_unregister);
  74
  75 MODULE_AUTHOR("John Heffner");
  76 MODULE_LICENSE("GPL");
  77 MODULE_DESCRIPTION("Scalable TCP");