240 lines
6.6 KiB
C
240 lines
6.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
*
|
|
* YeAH TCP
|
|
*
|
|
* For further details look at:
|
|
* https://web.archive.org/web/20080316215752/http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdf
|
|
*
|
|
*/
|
|
#include <linux/mm.h>
|
|
#include <linux/module.h>
|
|
#include <linux/skbuff.h>
|
|
#include <linux/inet_diag.h>
|
|
|
|
#include <net/tcp.h>
|
|
|
|
#include "tcp_vegas.h"
|
|
|
|
#define TCP_YEAH_ALPHA 80 /* number of packets queued at the bottleneck */
|
|
#define TCP_YEAH_GAMMA 1 /* fraction of queue to be removed per rtt */
|
|
#define TCP_YEAH_DELTA 3 /* log minimum fraction of cwnd to be removed on loss */
|
|
#define TCP_YEAH_EPSILON 1 /* log maximum fraction to be removed on early decongestion */
|
|
#define TCP_YEAH_PHY 8 /* maximum delta from base */
|
|
#define TCP_YEAH_RHO 16 /* minimum number of consecutive rtt to consider competition on loss */
|
|
#define TCP_YEAH_ZETA 50 /* minimum number of state switches to reset reno_count */
|
|
|
|
#define TCP_SCALABLE_AI_CNT 100U
|
|
|
|
/* YeAH variables */
|
|
struct yeah {
|
|
struct vegas vegas; /* must be first */
|
|
|
|
/* YeAH */
|
|
u32 lastQ;
|
|
u32 doing_reno_now;
|
|
|
|
u32 reno_count;
|
|
u32 fast_count;
|
|
};
|
|
|
|
static void tcp_yeah_init(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct yeah *yeah = inet_csk_ca(sk);
|
|
|
|
tcp_vegas_init(sk);
|
|
|
|
yeah->doing_reno_now = 0;
|
|
yeah->lastQ = 0;
|
|
|
|
yeah->reno_count = 2;
|
|
|
|
/* 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 tcp_yeah_cong_avoid(struct sock *sk, u32 ack, u32 acked)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct yeah *yeah = inet_csk_ca(sk);
|
|
|
|
if (!tcp_is_cwnd_limited(sk))
|
|
return;
|
|
|
|
if (tcp_in_slow_start(tp)) {
|
|
acked = tcp_slow_start(tp, acked);
|
|
if (!acked)
|
|
goto do_vegas;
|
|
}
|
|
|
|
if (!yeah->doing_reno_now) {
|
|
/* Scalable */
|
|
tcp_cong_avoid_ai(tp, min(tcp_snd_cwnd(tp), TCP_SCALABLE_AI_CNT),
|
|
acked);
|
|
} else {
|
|
/* Reno */
|
|
tcp_cong_avoid_ai(tp, tcp_snd_cwnd(tp), acked);
|
|
}
|
|
|
|
/* The key players are v_vegas.beg_snd_una and v_beg_snd_nxt.
|
|
*
|
|
* These are so named because they represent the approximate values
|
|
* of snd_una and snd_nxt at the beginning of the current RTT. More
|
|
* precisely, they represent the amount of data sent during the RTT.
|
|
* At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
|
|
* we will calculate that (v_beg_snd_nxt - v_vegas.beg_snd_una) outstanding
|
|
* bytes of data have been ACKed during the course of the RTT, giving
|
|
* an "actual" rate of:
|
|
*
|
|
* (v_beg_snd_nxt - v_vegas.beg_snd_una) / (rtt duration)
|
|
*
|
|
* Unfortunately, v_vegas.beg_snd_una is not exactly equal to snd_una,
|
|
* because delayed ACKs can cover more than one segment, so they
|
|
* don't line up yeahly with the boundaries of RTTs.
|
|
*
|
|
* Another unfortunate fact of life is that delayed ACKs delay the
|
|
* advance of the left edge of our send window, so that the number
|
|
* of bytes we send in an RTT is often less than our cwnd will allow.
|
|
* So we keep track of our cwnd separately, in v_beg_snd_cwnd.
|
|
*/
|
|
do_vegas:
|
|
if (after(ack, yeah->vegas.beg_snd_nxt)) {
|
|
/* We do the Vegas calculations only if we got enough RTT
|
|
* samples that we can be reasonably sure that we got
|
|
* at least one RTT sample that wasn't from a delayed ACK.
|
|
* If we only had 2 samples total,
|
|
* then that means we're getting only 1 ACK per RTT, which
|
|
* means they're almost certainly delayed ACKs.
|
|
* If we have 3 samples, we should be OK.
|
|
*/
|
|
|
|
if (yeah->vegas.cntRTT > 2) {
|
|
u32 rtt, queue;
|
|
u64 bw;
|
|
|
|
/* We have enough RTT samples, so, using the Vegas
|
|
* algorithm, we determine if we should increase or
|
|
* decrease cwnd, and by how much.
|
|
*/
|
|
|
|
/* Pluck out the RTT we are using for the Vegas
|
|
* calculations. This is the min RTT seen during the
|
|
* last RTT. Taking the min filters out the effects
|
|
* of delayed ACKs, at the cost of noticing congestion
|
|
* a bit later.
|
|
*/
|
|
rtt = yeah->vegas.minRTT;
|
|
|
|
/* Compute excess number of packets above bandwidth
|
|
* Avoid doing full 64 bit divide.
|
|
*/
|
|
bw = tcp_snd_cwnd(tp);
|
|
bw *= rtt - yeah->vegas.baseRTT;
|
|
do_div(bw, rtt);
|
|
queue = bw;
|
|
|
|
if (queue > TCP_YEAH_ALPHA ||
|
|
rtt - yeah->vegas.baseRTT > (yeah->vegas.baseRTT / TCP_YEAH_PHY)) {
|
|
if (queue > TCP_YEAH_ALPHA &&
|
|
tcp_snd_cwnd(tp) > yeah->reno_count) {
|
|
u32 reduction = min(queue / TCP_YEAH_GAMMA ,
|
|
tcp_snd_cwnd(tp) >> TCP_YEAH_EPSILON);
|
|
|
|
tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) - reduction);
|
|
|
|
tcp_snd_cwnd_set(tp, max(tcp_snd_cwnd(tp),
|
|
yeah->reno_count));
|
|
|
|
tp->snd_ssthresh = tcp_snd_cwnd(tp);
|
|
}
|
|
|
|
if (yeah->reno_count <= 2)
|
|
yeah->reno_count = max(tcp_snd_cwnd(tp)>>1, 2U);
|
|
else
|
|
yeah->reno_count++;
|
|
|
|
yeah->doing_reno_now = min(yeah->doing_reno_now + 1,
|
|
0xffffffU);
|
|
} else {
|
|
yeah->fast_count++;
|
|
|
|
if (yeah->fast_count > TCP_YEAH_ZETA) {
|
|
yeah->reno_count = 2;
|
|
yeah->fast_count = 0;
|
|
}
|
|
|
|
yeah->doing_reno_now = 0;
|
|
}
|
|
|
|
yeah->lastQ = queue;
|
|
}
|
|
|
|
/* Save the extent of the current window so we can use this
|
|
* at the end of the next RTT.
|
|
*/
|
|
yeah->vegas.beg_snd_una = yeah->vegas.beg_snd_nxt;
|
|
yeah->vegas.beg_snd_nxt = tp->snd_nxt;
|
|
yeah->vegas.beg_snd_cwnd = tcp_snd_cwnd(tp);
|
|
|
|
/* Wipe the slate clean for the next RTT. */
|
|
yeah->vegas.cntRTT = 0;
|
|
yeah->vegas.minRTT = 0x7fffffff;
|
|
}
|
|
}
|
|
|
|
static u32 tcp_yeah_ssthresh(struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
struct yeah *yeah = inet_csk_ca(sk);
|
|
u32 reduction;
|
|
|
|
if (yeah->doing_reno_now < TCP_YEAH_RHO) {
|
|
reduction = yeah->lastQ;
|
|
|
|
reduction = min(reduction, max(tcp_snd_cwnd(tp)>>1, 2U));
|
|
|
|
reduction = max(reduction, tcp_snd_cwnd(tp) >> TCP_YEAH_DELTA);
|
|
} else
|
|
reduction = max(tcp_snd_cwnd(tp)>>1, 2U);
|
|
|
|
yeah->fast_count = 0;
|
|
yeah->reno_count = max(yeah->reno_count>>1, 2U);
|
|
|
|
return max_t(int, tcp_snd_cwnd(tp) - reduction, 2);
|
|
}
|
|
|
|
static struct tcp_congestion_ops tcp_yeah __read_mostly = {
|
|
.init = tcp_yeah_init,
|
|
.ssthresh = tcp_yeah_ssthresh,
|
|
.undo_cwnd = tcp_reno_undo_cwnd,
|
|
.cong_avoid = tcp_yeah_cong_avoid,
|
|
.set_state = tcp_vegas_state,
|
|
.cwnd_event = tcp_vegas_cwnd_event,
|
|
.get_info = tcp_vegas_get_info,
|
|
.pkts_acked = tcp_vegas_pkts_acked,
|
|
|
|
.owner = THIS_MODULE,
|
|
.name = "yeah",
|
|
};
|
|
|
|
static int __init tcp_yeah_register(void)
|
|
{
|
|
BUILD_BUG_ON(sizeof(struct yeah) > ICSK_CA_PRIV_SIZE);
|
|
tcp_register_congestion_control(&tcp_yeah);
|
|
return 0;
|
|
}
|
|
|
|
static void __exit tcp_yeah_unregister(void)
|
|
{
|
|
tcp_unregister_congestion_control(&tcp_yeah);
|
|
}
|
|
|
|
module_init(tcp_yeah_register);
|
|
module_exit(tcp_yeah_unregister);
|
|
|
|
MODULE_AUTHOR("Angelo P. Castellani");
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_DESCRIPTION("YeAH TCP");
|