[linux-block.git] / net / ipv4 / tcp_scalable.c

// SPDX-License-Identifier: GPL-2.0-only
/* Tom Kelly's Scalable TCP
 *
 * See http://www.deneholme.net/tom/scalable/
 *
 * John Heffner <jheffner@sc.edu>
 */

#include <linux/module.h>
#include <net/tcp.h>

/* These factors derived from the recommended values in the aer:
 * .01 and and 7/8. We use 50 instead of 100 to account for
 * delayed ack.
 */
#define TCP_SCALABLE_AI_CNT	50U
#define TCP_SCALABLE_MD_SCALE	3

static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
{
	struct tcp_sock *tp = tcp_sk(sk);

	if (!tcp_is_cwnd_limited(sk))
		return;

	if (tcp_in_slow_start(tp))
		tcp_slow_start(tp, acked);
	else
		tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
				  1);
}

static u32 tcp_scalable_ssthresh(struct sock *sk)
{
	const struct tcp_sock *tp = tcp_sk(sk);

	return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
}

static struct tcp_congestion_ops tcp_scalable __read_mostly = {
	.ssthresh	= tcp_scalable_ssthresh,
	.undo_cwnd	= tcp_reno_undo_cwnd,
	.cong_avoid	= tcp_scalable_cong_avoid,

	.owner		= THIS_MODULE,
	.name		= "scalable",
};

static int __init tcp_scalable_register(void)
{
	return tcp_register_congestion_control(&tcp_scalable);
}

static void __exit tcp_scalable_unregister(void)
{
	tcp_unregister_congestion_control(&tcp_scalable);
}

module_init(tcp_scalable_register);
module_exit(tcp_scalable_unregister);

MODULE_AUTHOR("John Heffner");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Scalable TCP");
Commit	Line	Data
09c434b8	1	// SPDX-License-Identifier: GPL-2.0-only
0e57976b JH	2	/* Tom Kelly's Scalable TCP
0e57976b JH	3	*
a52b8bd3	4	* See http://www.deneholme.net/tom/scalable/
0e57976b JH	5	*
	6	* John Heffner <jheffner@sc.edu>
	7	*/
	8
0e57976b JH	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
24901551	19	static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
0e57976b	20	{
6687e988	21	struct tcp_sock *tp = tcp_sk(sk);
f4805ede	22
24901551	23	if (!tcp_is_cwnd_limited(sk))
0e57976b JH	24	return;
0e57976b JH	25
071d5080	26	if (tcp_in_slow_start(tp))
9f9843a7	27	tcp_slow_start(tp, acked);
758ce5c8	28	else
e73ebb08 NC	29	tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
e73ebb08 NC	30	1);
0e57976b JH	31	}
0e57976b JH	32
6687e988	33	static u32 tcp_scalable_ssthresh(struct sock *sk)
0e57976b	34	{
6687e988	35	const struct tcp_sock *tp = tcp_sk(sk);
688d1945	36
0e57976b JH	37	return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
	38	}
	39
a252bebe	40	static struct tcp_congestion_ops tcp_scalable __read_mostly = {
0e57976b	41	.ssthresh = tcp_scalable_ssthresh,
f1722a1b	42	.undo_cwnd = tcp_reno_undo_cwnd,
0e57976b	43	.cong_avoid = tcp_scalable_cong_avoid,
0e57976b JH	44
	45	.owner = THIS_MODULE,
	46	.name = "scalable",
	47	};
	48
	49	static int __init tcp_scalable_register(void)
	50	{
	51	return tcp_register_congestion_control(&tcp_scalable);
	52	}
	53
	54	static void __exit tcp_scalable_unregister(void)
	55	{
	56	tcp_unregister_congestion_control(&tcp_scalable);
	57	}
	58
	59	module_init(tcp_scalable_register);
	60	module_exit(tcp_scalable_unregister);
	61
	62	MODULE_AUTHOR("John Heffner");
	63	MODULE_LICENSE("GPL");
	64	MODULE_DESCRIPTION("Scalable TCP");