linux/net/ipv4/tcp_highspeed.c
Yuchung Cheng f1722a1be1 tcp: consolidate congestion control undo functions
Most TCP congestion controls are using identical logic to undo
cwnd except BBR. This patch consolidates these similar functions
to the one used currently by Reno and others.

Suggested-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-06 21:25:10 -07:00

186 lines
4.9 KiB
C

/*
* Sally Floyd's High Speed TCP (RFC 3649) congestion control
*
* See http://www.icir.org/floyd/hstcp.html
*
* John Heffner <jheffner@psc.edu>
*/
#include <linux/module.h>
#include <net/tcp.h>
/* From AIMD tables from RFC 3649 appendix B,
* with fixed-point MD scaled <<8.
*/
static const struct hstcp_aimd_val {
unsigned int cwnd;
unsigned int md;
} hstcp_aimd_vals[] = {
{ 38, 128, /* 0.50 */ },
{ 118, 112, /* 0.44 */ },
{ 221, 104, /* 0.41 */ },
{ 347, 98, /* 0.38 */ },
{ 495, 93, /* 0.37 */ },
{ 663, 89, /* 0.35 */ },
{ 851, 86, /* 0.34 */ },
{ 1058, 83, /* 0.33 */ },
{ 1284, 81, /* 0.32 */ },
{ 1529, 78, /* 0.31 */ },
{ 1793, 76, /* 0.30 */ },
{ 2076, 74, /* 0.29 */ },
{ 2378, 72, /* 0.28 */ },
{ 2699, 71, /* 0.28 */ },
{ 3039, 69, /* 0.27 */ },
{ 3399, 68, /* 0.27 */ },
{ 3778, 66, /* 0.26 */ },
{ 4177, 65, /* 0.26 */ },
{ 4596, 64, /* 0.25 */ },
{ 5036, 62, /* 0.25 */ },
{ 5497, 61, /* 0.24 */ },
{ 5979, 60, /* 0.24 */ },
{ 6483, 59, /* 0.23 */ },
{ 7009, 58, /* 0.23 */ },
{ 7558, 57, /* 0.22 */ },
{ 8130, 56, /* 0.22 */ },
{ 8726, 55, /* 0.22 */ },
{ 9346, 54, /* 0.21 */ },
{ 9991, 53, /* 0.21 */ },
{ 10661, 52, /* 0.21 */ },
{ 11358, 52, /* 0.20 */ },
{ 12082, 51, /* 0.20 */ },
{ 12834, 50, /* 0.20 */ },
{ 13614, 49, /* 0.19 */ },
{ 14424, 48, /* 0.19 */ },
{ 15265, 48, /* 0.19 */ },
{ 16137, 47, /* 0.19 */ },
{ 17042, 46, /* 0.18 */ },
{ 17981, 45, /* 0.18 */ },
{ 18955, 45, /* 0.18 */ },
{ 19965, 44, /* 0.17 */ },
{ 21013, 43, /* 0.17 */ },
{ 22101, 43, /* 0.17 */ },
{ 23230, 42, /* 0.17 */ },
{ 24402, 41, /* 0.16 */ },
{ 25618, 41, /* 0.16 */ },
{ 26881, 40, /* 0.16 */ },
{ 28193, 39, /* 0.16 */ },
{ 29557, 39, /* 0.15 */ },
{ 30975, 38, /* 0.15 */ },
{ 32450, 38, /* 0.15 */ },
{ 33986, 37, /* 0.15 */ },
{ 35586, 36, /* 0.14 */ },
{ 37253, 36, /* 0.14 */ },
{ 38992, 35, /* 0.14 */ },
{ 40808, 35, /* 0.14 */ },
{ 42707, 34, /* 0.13 */ },
{ 44694, 33, /* 0.13 */ },
{ 46776, 33, /* 0.13 */ },
{ 48961, 32, /* 0.13 */ },
{ 51258, 32, /* 0.13 */ },
{ 53677, 31, /* 0.12 */ },
{ 56230, 30, /* 0.12 */ },
{ 58932, 30, /* 0.12 */ },
{ 61799, 29, /* 0.12 */ },
{ 64851, 28, /* 0.11 */ },
{ 68113, 28, /* 0.11 */ },
{ 71617, 27, /* 0.11 */ },
{ 75401, 26, /* 0.10 */ },
{ 79517, 26, /* 0.10 */ },
{ 84035, 25, /* 0.10 */ },
{ 89053, 24, /* 0.10 */ },
};
#define HSTCP_AIMD_MAX ARRAY_SIZE(hstcp_aimd_vals)
struct hstcp {
u32 ai;
};
static void hstcp_init(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);
struct hstcp *ca = inet_csk_ca(sk);
ca->ai = 0;
/* Ensure the MD arithmetic works. This is somewhat pedantic,
* since I don't think we will see a cwnd this large. :) */
tp->snd_cwnd_clamp = min_t(u32, tp->snd_cwnd_clamp, 0xffffffff/128);
}
static void hstcp_cong_avoid(struct sock *sk, u32 ack, u32 acked)
{
struct tcp_sock *tp = tcp_sk(sk);
struct hstcp *ca = inet_csk_ca(sk);
if (!tcp_is_cwnd_limited(sk))
return;
if (tcp_in_slow_start(tp))
tcp_slow_start(tp, acked);
else {
/* Update AIMD parameters.
*
* We want to guarantee that:
* hstcp_aimd_vals[ca->ai-1].cwnd <
* snd_cwnd <=
* hstcp_aimd_vals[ca->ai].cwnd
*/
if (tp->snd_cwnd > hstcp_aimd_vals[ca->ai].cwnd) {
while (tp->snd_cwnd > hstcp_aimd_vals[ca->ai].cwnd &&
ca->ai < HSTCP_AIMD_MAX - 1)
ca->ai++;
} else if (ca->ai && tp->snd_cwnd <= hstcp_aimd_vals[ca->ai-1].cwnd) {
while (ca->ai && tp->snd_cwnd <= hstcp_aimd_vals[ca->ai-1].cwnd)
ca->ai--;
}
/* Do additive increase */
if (tp->snd_cwnd < tp->snd_cwnd_clamp) {
/* cwnd = cwnd + a(w) / cwnd */
tp->snd_cwnd_cnt += ca->ai + 1;
if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
tp->snd_cwnd_cnt -= tp->snd_cwnd;
tp->snd_cwnd++;
}
}
}
}
static u32 hstcp_ssthresh(struct sock *sk)
{
const struct tcp_sock *tp = tcp_sk(sk);
struct hstcp *ca = inet_csk_ca(sk);
/* Do multiplicative decrease */
return max(tp->snd_cwnd - ((tp->snd_cwnd * hstcp_aimd_vals[ca->ai].md) >> 8), 2U);
}
static struct tcp_congestion_ops tcp_highspeed __read_mostly = {
.init = hstcp_init,
.ssthresh = hstcp_ssthresh,
.undo_cwnd = tcp_reno_undo_cwnd,
.cong_avoid = hstcp_cong_avoid,
.owner = THIS_MODULE,
.name = "highspeed"
};
static int __init hstcp_register(void)
{
BUILD_BUG_ON(sizeof(struct hstcp) > ICSK_CA_PRIV_SIZE);
return tcp_register_congestion_control(&tcp_highspeed);
}
static void __exit hstcp_unregister(void)
{
tcp_unregister_congestion_control(&tcp_highspeed);
}
module_init(hstcp_register);
module_exit(hstcp_unregister);
MODULE_AUTHOR("John Heffner");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("High Speed TCP");