mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 19:00:25 +00:00
![Alexey Dobriyan](/assets/img/avatar_default.png)
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
304 lines
7.3 KiB
C
304 lines
7.3 KiB
C
/*
|
|
* H-TCP congestion control. The algorithm is detailed in:
|
|
* R.N.Shorten, D.J.Leith:
|
|
* "H-TCP: TCP for high-speed and long-distance networks"
|
|
* Proc. PFLDnet, Argonne, 2004.
|
|
* http://www.hamilton.ie/net/htcp3.pdf
|
|
*/
|
|
|
|
#include <linux/mm.h>
|
|
#include <linux/module.h>
|
|
#include <net/tcp.h>
|
|
|
|
#define ALPHA_BASE (1<<7) /* 1.0 with shift << 7 */
|
|
#define BETA_MIN (1<<6) /* 0.5 with shift << 7 */
|
|
#define BETA_MAX 102 /* 0.8 with shift << 7 */
|
|
|
|
static int use_rtt_scaling = 1;
|
|
module_param(use_rtt_scaling, int, 0644);
|
|
MODULE_PARM_DESC(use_rtt_scaling, "turn on/off RTT scaling");
|
|
|
|
static int use_bandwidth_switch = 1;
|
|
module_param(use_bandwidth_switch, int, 0644);
|
|
MODULE_PARM_DESC(use_bandwidth_switch, "turn on/off bandwidth switcher");
|
|
|
|
struct htcp {
|
|
u16 alpha; /* Fixed point arith, << 7 */
|
|
u8 beta; /* Fixed point arith, << 7 */
|
|
u8 modeswitch; /* Delay modeswitch until we had at least one congestion event */
|
|
u32 last_cong; /* Time since last congestion event end */
|
|
u32 undo_last_cong;
|
|
u16 pkts_acked;
|
|
u32 packetcount;
|
|
u32 minRTT;
|
|
u32 maxRTT;
|
|
|
|
u32 undo_maxRTT;
|
|
u32 undo_old_maxB;
|
|
|
|
/* Bandwidth estimation */
|
|
u32 minB;
|
|
u32 maxB;
|
|
u32 old_maxB;
|
|
u32 Bi;
|
|
u32 lasttime;
|
|
};
|
|
|
|
static inline u32 htcp_cong_time(struct htcp *ca)
|
|
{
|
|
return jiffies - ca->last_cong;
|
|
}
|
|
|
|
static inline u32 htcp_ccount(struct htcp *ca)
|
|
{
|
|
return htcp_cong_time(ca)/ca->minRTT;
|
|
}
|
|
|
|
static inline void htcp_reset(struct htcp *ca)
|
|
{
|
|
ca->undo_last_cong = ca->last_cong;
|
|
ca->undo_maxRTT = ca->maxRTT;
|
|
ca->undo_old_maxB = ca->old_maxB;
|
|
|
|
ca->last_cong = jiffies;
|
|
}
|
|
|
|
static u32 htcp_cwnd_undo(struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
struct htcp *ca = inet_csk_ca(sk);
|
|
ca->last_cong = ca->undo_last_cong;
|
|
ca->maxRTT = ca->undo_maxRTT;
|
|
ca->old_maxB = ca->undo_old_maxB;
|
|
return max(tp->snd_cwnd, (tp->snd_ssthresh<<7)/ca->beta);
|
|
}
|
|
|
|
static inline void measure_rtt(struct sock *sk)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
struct htcp *ca = inet_csk_ca(sk);
|
|
u32 srtt = tp->srtt>>3;
|
|
|
|
/* keep track of minimum RTT seen so far, minRTT is zero at first */
|
|
if (ca->minRTT > srtt || !ca->minRTT)
|
|
ca->minRTT = srtt;
|
|
|
|
/* max RTT */
|
|
if (icsk->icsk_ca_state == TCP_CA_Open && tp->snd_ssthresh < 0xFFFF && htcp_ccount(ca) > 3) {
|
|
if (ca->maxRTT < ca->minRTT)
|
|
ca->maxRTT = ca->minRTT;
|
|
if (ca->maxRTT < srtt && srtt <= ca->maxRTT+msecs_to_jiffies(20))
|
|
ca->maxRTT = srtt;
|
|
}
|
|
}
|
|
|
|
static void measure_achieved_throughput(struct sock *sk, u32 pkts_acked)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
struct htcp *ca = inet_csk_ca(sk);
|
|
u32 now = tcp_time_stamp;
|
|
|
|
if (icsk->icsk_ca_state == TCP_CA_Open)
|
|
ca->pkts_acked = pkts_acked;
|
|
|
|
if (!use_bandwidth_switch)
|
|
return;
|
|
|
|
/* achieved throughput calculations */
|
|
if (icsk->icsk_ca_state != TCP_CA_Open &&
|
|
icsk->icsk_ca_state != TCP_CA_Disorder) {
|
|
ca->packetcount = 0;
|
|
ca->lasttime = now;
|
|
return;
|
|
}
|
|
|
|
ca->packetcount += pkts_acked;
|
|
|
|
if (ca->packetcount >= tp->snd_cwnd - (ca->alpha>>7? : 1)
|
|
&& now - ca->lasttime >= ca->minRTT
|
|
&& ca->minRTT > 0) {
|
|
__u32 cur_Bi = ca->packetcount*HZ/(now - ca->lasttime);
|
|
if (htcp_ccount(ca) <= 3) {
|
|
/* just after backoff */
|
|
ca->minB = ca->maxB = ca->Bi = cur_Bi;
|
|
} else {
|
|
ca->Bi = (3*ca->Bi + cur_Bi)/4;
|
|
if (ca->Bi > ca->maxB)
|
|
ca->maxB = ca->Bi;
|
|
if (ca->minB > ca->maxB)
|
|
ca->minB = ca->maxB;
|
|
}
|
|
ca->packetcount = 0;
|
|
ca->lasttime = now;
|
|
}
|
|
}
|
|
|
|
static inline void htcp_beta_update(struct htcp *ca, u32 minRTT, u32 maxRTT)
|
|
{
|
|
if (use_bandwidth_switch) {
|
|
u32 maxB = ca->maxB;
|
|
u32 old_maxB = ca->old_maxB;
|
|
ca->old_maxB = ca->maxB;
|
|
|
|
if (!between(5*maxB, 4*old_maxB, 6*old_maxB)) {
|
|
ca->beta = BETA_MIN;
|
|
ca->modeswitch = 0;
|
|
return;
|
|
}
|
|
}
|
|
|
|
if (ca->modeswitch && minRTT > msecs_to_jiffies(10) && maxRTT) {
|
|
ca->beta = (minRTT<<7)/maxRTT;
|
|
if (ca->beta < BETA_MIN)
|
|
ca->beta = BETA_MIN;
|
|
else if (ca->beta > BETA_MAX)
|
|
ca->beta = BETA_MAX;
|
|
} else {
|
|
ca->beta = BETA_MIN;
|
|
ca->modeswitch = 1;
|
|
}
|
|
}
|
|
|
|
static inline void htcp_alpha_update(struct htcp *ca)
|
|
{
|
|
u32 minRTT = ca->minRTT;
|
|
u32 factor = 1;
|
|
u32 diff = htcp_cong_time(ca);
|
|
|
|
if (diff > HZ) {
|
|
diff -= HZ;
|
|
factor = 1+ ( 10*diff + ((diff/2)*(diff/2)/HZ) )/HZ;
|
|
}
|
|
|
|
if (use_rtt_scaling && minRTT) {
|
|
u32 scale = (HZ<<3)/(10*minRTT);
|
|
scale = min(max(scale, 1U<<2), 10U<<3); /* clamping ratio to interval [0.5,10]<<3 */
|
|
factor = (factor<<3)/scale;
|
|
if (!factor)
|
|
factor = 1;
|
|
}
|
|
|
|
ca->alpha = 2*factor*((1<<7)-ca->beta);
|
|
if (!ca->alpha)
|
|
ca->alpha = ALPHA_BASE;
|
|
}
|
|
|
|
/* After we have the rtt data to calculate beta, we'd still prefer to wait one
|
|
* rtt before we adjust our beta to ensure we are working from a consistent
|
|
* data.
|
|
*
|
|
* This function should be called when we hit a congestion event since only at
|
|
* that point do we really have a real sense of maxRTT (the queues en route
|
|
* were getting just too full now).
|
|
*/
|
|
static void htcp_param_update(struct sock *sk)
|
|
{
|
|
struct htcp *ca = inet_csk_ca(sk);
|
|
u32 minRTT = ca->minRTT;
|
|
u32 maxRTT = ca->maxRTT;
|
|
|
|
htcp_beta_update(ca, minRTT, maxRTT);
|
|
htcp_alpha_update(ca);
|
|
|
|
/* add slowly fading memory for maxRTT to accommodate routing changes etc */
|
|
if (minRTT > 0 && maxRTT > minRTT)
|
|
ca->maxRTT = minRTT + ((maxRTT-minRTT)*95)/100;
|
|
}
|
|
|
|
static u32 htcp_recalc_ssthresh(struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
const struct htcp *ca = inet_csk_ca(sk);
|
|
htcp_param_update(sk);
|
|
return max((tp->snd_cwnd * ca->beta) >> 7, 2U);
|
|
}
|
|
|
|
static void htcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
|
|
u32 in_flight, int data_acked)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct htcp *ca = inet_csk_ca(sk);
|
|
|
|
if (!tcp_is_cwnd_limited(sk, in_flight))
|
|
return;
|
|
|
|
if (tp->snd_cwnd <= tp->snd_ssthresh)
|
|
tcp_slow_start(tp);
|
|
else {
|
|
|
|
measure_rtt(sk);
|
|
|
|
/* In dangerous area, increase slowly.
|
|
* In theory this is tp->snd_cwnd += alpha / tp->snd_cwnd
|
|
*/
|
|
if ((tp->snd_cwnd_cnt * ca->alpha)>>7 >= tp->snd_cwnd) {
|
|
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
|
|
tp->snd_cwnd++;
|
|
tp->snd_cwnd_cnt = 0;
|
|
htcp_alpha_update(ca);
|
|
} else
|
|
tp->snd_cwnd_cnt += ca->pkts_acked;
|
|
|
|
ca->pkts_acked = 1;
|
|
}
|
|
}
|
|
|
|
static void htcp_init(struct sock *sk)
|
|
{
|
|
struct htcp *ca = inet_csk_ca(sk);
|
|
|
|
memset(ca, 0, sizeof(struct htcp));
|
|
ca->alpha = ALPHA_BASE;
|
|
ca->beta = BETA_MIN;
|
|
ca->pkts_acked = 1;
|
|
ca->last_cong = jiffies;
|
|
}
|
|
|
|
static void htcp_state(struct sock *sk, u8 new_state)
|
|
{
|
|
switch (new_state) {
|
|
case TCP_CA_Open:
|
|
{
|
|
struct htcp *ca = inet_csk_ca(sk);
|
|
ca->last_cong = jiffies;
|
|
}
|
|
break;
|
|
case TCP_CA_CWR:
|
|
case TCP_CA_Recovery:
|
|
case TCP_CA_Loss:
|
|
htcp_reset(inet_csk_ca(sk));
|
|
break;
|
|
}
|
|
}
|
|
|
|
static struct tcp_congestion_ops htcp = {
|
|
.init = htcp_init,
|
|
.ssthresh = htcp_recalc_ssthresh,
|
|
.cong_avoid = htcp_cong_avoid,
|
|
.set_state = htcp_state,
|
|
.undo_cwnd = htcp_cwnd_undo,
|
|
.pkts_acked = measure_achieved_throughput,
|
|
.owner = THIS_MODULE,
|
|
.name = "htcp",
|
|
};
|
|
|
|
static int __init htcp_register(void)
|
|
{
|
|
BUILD_BUG_ON(sizeof(struct htcp) > ICSK_CA_PRIV_SIZE);
|
|
BUILD_BUG_ON(BETA_MIN >= BETA_MAX);
|
|
return tcp_register_congestion_control(&htcp);
|
|
}
|
|
|
|
static void __exit htcp_unregister(void)
|
|
{
|
|
tcp_unregister_congestion_control(&htcp);
|
|
}
|
|
|
|
module_init(htcp_register);
|
|
module_exit(htcp_unregister);
|
|
|
|
MODULE_AUTHOR("Baruch Even");
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_DESCRIPTION("H-TCP");
|