Merge master.kernel.org:/pub/scm/linux/kernel/git/davej/cpufreq
[linux-2.6] / net / ipv4 / tcp_scalable.c
1 /* Tom Kelly's Scalable TCP
2  *
3  * See htt://www-lce.eng.cam.ac.uk/~ctk21/scalable/
4  *
5  * John Heffner <jheffner@sc.edu>
6  */
7
8 #include <linux/config.h>
9 #include <linux/module.h>
10 #include <net/tcp.h>
11
12 /* These factors derived from the recommended values in the aer:
13  * .01 and and 7/8. We use 50 instead of 100 to account for
14  * delayed ack.
15  */
16 #define TCP_SCALABLE_AI_CNT     50U
17 #define TCP_SCALABLE_MD_SCALE   3
18
19 static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
20                                     u32 in_flight, int flag)
21 {
22         struct tcp_sock *tp = tcp_sk(sk);
23
24         if (!tcp_is_cwnd_limited(sk, in_flight))
25                 return;
26
27         if (tp->snd_cwnd <= tp->snd_ssthresh)
28                 tcp_slow_start(tp);
29         else {
30                 tp->snd_cwnd_cnt++;
31                 if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){
32                         if (tp->snd_cwnd < tp->snd_cwnd_clamp)
33                                 tp->snd_cwnd++;
34                         tp->snd_cwnd_cnt = 0;
35                 }
36         }
37 }
38
39 static u32 tcp_scalable_ssthresh(struct sock *sk)
40 {
41         const struct tcp_sock *tp = tcp_sk(sk);
42         return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
43 }
44
45
46 static struct tcp_congestion_ops tcp_scalable = {
47         .ssthresh       = tcp_scalable_ssthresh,
48         .cong_avoid     = tcp_scalable_cong_avoid,
49         .min_cwnd       = tcp_reno_min_cwnd,
50
51         .owner          = THIS_MODULE,
52         .name           = "scalable",
53 };
54
55 static int __init tcp_scalable_register(void)
56 {
57         return tcp_register_congestion_control(&tcp_scalable);
58 }
59
60 static void __exit tcp_scalable_unregister(void)
61 {
62         tcp_unregister_congestion_control(&tcp_scalable);
63 }
64
65 module_init(tcp_scalable_register);
66 module_exit(tcp_scalable_unregister);
67
68 MODULE_AUTHOR("John Heffner");
69 MODULE_LICENSE("GPL");
70 MODULE_DESCRIPTION("Scalable TCP");