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 static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
  19 {
  20         struct tcp_sock *tp = tcp_sk(sk);
  21
  22         if (!tcp_is_cwnd_limited(sk))
  23                 return;
  24
  25         if (tp->snd_cwnd <= tp->snd_ssthresh)
  26                 tcp_slow_start(tp, acked);
  27         else
  28                 tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
  29                                   1);
  30 }
  31
  32 static u32 tcp_scalable_ssthresh(struct sock *sk)
  33 {
  34         const struct tcp_sock *tp = tcp_sk(sk);
  35
  36         return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
  37 }
  38
  39 static struct tcp_congestion_ops tcp_scalable __read_mostly = {
  40         .ssthresh       = tcp_scalable_ssthresh,
  41         .cong_avoid     = tcp_scalable_cong_avoid,
  42
  43         .owner          = THIS_MODULE,
  44         .name           = "scalable",
  45 };
  46
  47 static int __init tcp_scalable_register(void)
  48 {
  49         return tcp_register_congestion_control(&tcp_scalable);
  50 }
  51
  52 static void __exit tcp_scalable_unregister(void)
  53 {
  54         tcp_unregister_congestion_control(&tcp_scalable);
  55 }
  56
  57 module_init(tcp_scalable_register);
  58 module_exit(tcp_scalable_unregister);
  59
  60 MODULE_AUTHOR("John Heffner");
  61 MODULE_LICENSE("GPL");
  62 MODULE_DESCRIPTION("Scalable TCP");