0e57976b63
This patch implements Tom Kelly's Scalable TCP congestion control algorithm for the modular framework. The algorithm has some nice scaling properties, and has been used a fair bit in research, though is known to have significant fairness issues, so it's not really suitable for general purpose use. Signed-off-by: John Heffner <jheffner@psc.edu> Signed-off-by: David S. Miller <davem@davemloft.net>
68 lines
1.6 KiB
C
68 lines
1.6 KiB
C
/* Tom Kelly's Scalable TCP
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*
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* See htt://www-lce.eng.cam.ac.uk/~ctk21/scalable/
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*
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* John Heffner <jheffner@sc.edu>
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*/
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#include <linux/config.h>
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#include <linux/module.h>
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#include <net/tcp.h>
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/* These factors derived from the recommended values in the aer:
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* .01 and and 7/8. We use 50 instead of 100 to account for
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* delayed ack.
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*/
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#define TCP_SCALABLE_AI_CNT 50U
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#define TCP_SCALABLE_MD_SCALE 3
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static void tcp_scalable_cong_avoid(struct tcp_sock *tp, u32 ack, u32 rtt,
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u32 in_flight, int flag)
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{
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if (in_flight < tp->snd_cwnd)
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return;
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if (tp->snd_cwnd <= tp->snd_ssthresh) {
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tp->snd_cwnd++;
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} else {
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tp->snd_cwnd_cnt++;
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if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){
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tp->snd_cwnd++;
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tp->snd_cwnd_cnt = 0;
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}
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}
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tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
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tp->snd_cwnd_stamp = tcp_time_stamp;
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}
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static u32 tcp_scalable_ssthresh(struct tcp_sock *tp)
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{
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return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
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}
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static struct tcp_congestion_ops tcp_scalable = {
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.ssthresh = tcp_scalable_ssthresh,
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.cong_avoid = tcp_scalable_cong_avoid,
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.min_cwnd = tcp_reno_min_cwnd,
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.owner = THIS_MODULE,
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.name = "scalable",
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};
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static int __init tcp_scalable_register(void)
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{
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return tcp_register_congestion_control(&tcp_scalable);
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}
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static void __exit tcp_scalable_unregister(void)
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{
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tcp_unregister_congestion_control(&tcp_scalable);
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}
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module_init(tcp_scalable_register);
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module_exit(tcp_scalable_unregister);
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MODULE_AUTHOR("John Heffner");
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("Scalable TCP");
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