linux/net/ipv4/tcp_htcp.c
Arnaldo Carvalho de Melo 6687e988d9 [ICSK]: Move TCP congestion avoidance members to icsk
This changeset basically moves tcp_sk()->{ca_ops,ca_state,etc} to inet_csk(),
minimal renaming/moving done in this changeset to ease review.

Most of it is just changes of struct tcp_sock * to struct sock * parameters.

With this we move to a state closer to two interesting goals:

1. Generalisation of net/ipv4/tcp_diag.c, becoming inet_diag.c, being used
   for any INET transport protocol that has struct inet_hashinfo and are
   derived from struct inet_connection_sock. Keeps the userspace API, that will
   just not display DCCP sockets, while newer versions of tools can support
   DCCP.

2. INET generic transport pluggable Congestion Avoidance infrastructure, using
   the current TCP CA infrastructure with DCCP.

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2005-08-29 15:56:18 -07:00

298 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/config.h>
#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 */
u8 ccount; /* Number of RTTs since last congestion event */
u8 undo_ccount;
u16 packetcount;
u32 minRTT;
u32 maxRTT;
u32 snd_cwnd_cnt2;
u32 undo_maxRTT;
u32 undo_old_maxB;
/* Bandwidth estimation */
u32 minB;
u32 maxB;
u32 old_maxB;
u32 Bi;
u32 lasttime;
};
static inline void htcp_reset(struct htcp *ca)
{
ca->undo_ccount = ca->ccount;
ca->undo_maxRTT = ca->maxRTT;
ca->undo_old_maxB = ca->old_maxB;
ca->ccount = 0;
ca->snd_cwnd_cnt2 = 0;
}
static u32 htcp_cwnd_undo(struct sock *sk)
{
const struct tcp_sock *tp = tcp_sk(sk);
struct htcp *ca = inet_csk_ca(sk);
ca->ccount = ca->undo_ccount;
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 && ca->ccount > 3) {
if (ca->maxRTT < ca->minRTT)
ca->maxRTT = ca->minRTT;
if (ca->maxRTT < srtt && srtt <= ca->maxRTT+HZ/50)
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;
/* 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 (ca->ccount <= 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 > max(HZ/100, 1) && 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 = ca->ccount * minRTT; /* time since last backoff */
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 (in_flight < tp->snd_cwnd)
return;
if (tp->snd_cwnd <= tp->snd_ssthresh) {
/* In "safe" area, increase. */
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
} else {
measure_rtt(sk);
/* keep track of number of round-trip times since last backoff event */
if (ca->snd_cwnd_cnt2++ > tp->snd_cwnd) {
ca->ccount++;
ca->snd_cwnd_cnt2 = 0;
htcp_alpha_update(ca);
}
/* 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;
ca->ccount++;
}
}
}
/* Lower bound on congestion window. */
static u32 htcp_min_cwnd(struct sock *sk)
{
const struct tcp_sock *tp = tcp_sk(sk);
return tp->snd_ssthresh;
}
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;
}
static void htcp_state(struct sock *sk, u8 new_state)
{
switch (new_state) {
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,
.min_cwnd = htcp_min_cwnd,
.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)
{
BUG_ON(sizeof(struct htcp) > ICSK_CA_PRIV_SIZE);
BUILD_BUG_ON(BETA_MIN >= BETA_MAX);
if (!use_bandwidth_switch)
htcp.pkts_acked = NULL;
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");