mirror of
https://github.com/torvalds/linux.git
synced 2024-12-29 14:21:47 +00:00
74975d40b1
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
307 lines
8.2 KiB
C
307 lines
8.2 KiB
C
/*
|
|
* TCP Westwood+: end-to-end bandwidth estimation for TCP
|
|
*
|
|
* Angelo Dell'Aera: author of the first version of TCP Westwood+ in Linux 2.4
|
|
*
|
|
* Support at http://c3lab.poliba.it/index.php/Westwood
|
|
* Main references in literature:
|
|
*
|
|
* - Mascolo S, Casetti, M. Gerla et al.
|
|
* "TCP Westwood: bandwidth estimation for TCP" Proc. ACM Mobicom 2001
|
|
*
|
|
* - A. Grieco, s. Mascolo
|
|
* "Performance evaluation of New Reno, Vegas, Westwood+ TCP" ACM Computer
|
|
* Comm. Review, 2004
|
|
*
|
|
* - A. Dell'Aera, L. Grieco, S. Mascolo.
|
|
* "Linux 2.4 Implementation of Westwood+ TCP with Rate-Halving :
|
|
* A Performance Evaluation Over the Internet" (ICC 2004), Paris, June 2004
|
|
*
|
|
* Westwood+ employs end-to-end bandwidth measurement to set cwnd and
|
|
* ssthresh after packet loss. The probing phase is as the original Reno.
|
|
*/
|
|
|
|
#include <linux/mm.h>
|
|
#include <linux/module.h>
|
|
#include <linux/skbuff.h>
|
|
#include <linux/inet_diag.h>
|
|
#include <net/tcp.h>
|
|
|
|
/* TCP Westwood structure */
|
|
struct westwood {
|
|
u32 bw_ns_est; /* first bandwidth estimation..not too smoothed 8) */
|
|
u32 bw_est; /* bandwidth estimate */
|
|
u32 rtt_win_sx; /* here starts a new evaluation... */
|
|
u32 bk;
|
|
u32 snd_una; /* used for evaluating the number of acked bytes */
|
|
u32 cumul_ack;
|
|
u32 accounted;
|
|
u32 rtt;
|
|
u32 rtt_min; /* minimum observed RTT */
|
|
u8 first_ack; /* flag which infers that this is the first ack */
|
|
u8 reset_rtt_min; /* Reset RTT min to next RTT sample*/
|
|
};
|
|
|
|
|
|
/* TCP Westwood functions and constants */
|
|
#define TCP_WESTWOOD_RTT_MIN (HZ/20) /* 50ms */
|
|
#define TCP_WESTWOOD_INIT_RTT (20*HZ) /* maybe too conservative?! */
|
|
|
|
/*
|
|
* @tcp_westwood_create
|
|
* This function initializes fields used in TCP Westwood+,
|
|
* it is called after the initial SYN, so the sequence numbers
|
|
* are correct but new passive connections we have no
|
|
* information about RTTmin at this time so we simply set it to
|
|
* TCP_WESTWOOD_INIT_RTT. This value was chosen to be too conservative
|
|
* since in this way we're sure it will be updated in a consistent
|
|
* way as soon as possible. It will reasonably happen within the first
|
|
* RTT period of the connection lifetime.
|
|
*/
|
|
static void tcp_westwood_init(struct sock *sk)
|
|
{
|
|
struct westwood *w = inet_csk_ca(sk);
|
|
|
|
w->bk = 0;
|
|
w->bw_ns_est = 0;
|
|
w->bw_est = 0;
|
|
w->accounted = 0;
|
|
w->cumul_ack = 0;
|
|
w->reset_rtt_min = 1;
|
|
w->rtt_min = w->rtt = TCP_WESTWOOD_INIT_RTT;
|
|
w->rtt_win_sx = tcp_time_stamp;
|
|
w->snd_una = tcp_sk(sk)->snd_una;
|
|
w->first_ack = 1;
|
|
}
|
|
|
|
/*
|
|
* @westwood_do_filter
|
|
* Low-pass filter. Implemented using constant coefficients.
|
|
*/
|
|
static inline u32 westwood_do_filter(u32 a, u32 b)
|
|
{
|
|
return (((7 * a) + b) >> 3);
|
|
}
|
|
|
|
static void westwood_filter(struct westwood *w, u32 delta)
|
|
{
|
|
/* If the filter is empty fill it with the first sample of bandwidth */
|
|
if (w->bw_ns_est == 0 && w->bw_est == 0) {
|
|
w->bw_ns_est = w->bk / delta;
|
|
w->bw_est = w->bw_ns_est;
|
|
} else {
|
|
w->bw_ns_est = westwood_do_filter(w->bw_ns_est, w->bk / delta);
|
|
w->bw_est = westwood_do_filter(w->bw_est, w->bw_ns_est);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* @westwood_pkts_acked
|
|
* Called after processing group of packets.
|
|
* but all westwood needs is the last sample of srtt.
|
|
*/
|
|
static void tcp_westwood_pkts_acked(struct sock *sk, u32 cnt)
|
|
{
|
|
struct westwood *w = inet_csk_ca(sk);
|
|
if (cnt > 0)
|
|
w->rtt = tcp_sk(sk)->srtt >> 3;
|
|
}
|
|
|
|
/*
|
|
* @westwood_update_window
|
|
* It updates RTT evaluation window if it is the right moment to do
|
|
* it. If so it calls filter for evaluating bandwidth.
|
|
*/
|
|
static void westwood_update_window(struct sock *sk)
|
|
{
|
|
struct westwood *w = inet_csk_ca(sk);
|
|
s32 delta = tcp_time_stamp - w->rtt_win_sx;
|
|
|
|
/* Initialize w->snd_una with the first acked sequence number in order
|
|
* to fix mismatch between tp->snd_una and w->snd_una for the first
|
|
* bandwidth sample
|
|
*/
|
|
if (w->first_ack) {
|
|
w->snd_una = tcp_sk(sk)->snd_una;
|
|
w->first_ack = 0;
|
|
}
|
|
|
|
/*
|
|
* See if a RTT-window has passed.
|
|
* Be careful since if RTT is less than
|
|
* 50ms we don't filter but we continue 'building the sample'.
|
|
* This minimum limit was chosen since an estimation on small
|
|
* time intervals is better to avoid...
|
|
* Obviously on a LAN we reasonably will always have
|
|
* right_bound = left_bound + WESTWOOD_RTT_MIN
|
|
*/
|
|
if (w->rtt && delta > max_t(u32, w->rtt, TCP_WESTWOOD_RTT_MIN)) {
|
|
westwood_filter(w, delta);
|
|
|
|
w->bk = 0;
|
|
w->rtt_win_sx = tcp_time_stamp;
|
|
}
|
|
}
|
|
|
|
static inline void update_rtt_min(struct westwood *w)
|
|
{
|
|
if (w->reset_rtt_min) {
|
|
w->rtt_min = w->rtt;
|
|
w->reset_rtt_min = 0;
|
|
} else
|
|
w->rtt_min = min(w->rtt, w->rtt_min);
|
|
}
|
|
|
|
|
|
/*
|
|
* @westwood_fast_bw
|
|
* It is called when we are in fast path. In particular it is called when
|
|
* header prediction is successful. In such case in fact update is
|
|
* straight forward and doesn't need any particular care.
|
|
*/
|
|
static inline void westwood_fast_bw(struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
struct westwood *w = inet_csk_ca(sk);
|
|
|
|
westwood_update_window(sk);
|
|
|
|
w->bk += tp->snd_una - w->snd_una;
|
|
w->snd_una = tp->snd_una;
|
|
update_rtt_min(w);
|
|
}
|
|
|
|
/*
|
|
* @westwood_acked_count
|
|
* This function evaluates cumul_ack for evaluating bk in case of
|
|
* delayed or partial acks.
|
|
*/
|
|
static inline u32 westwood_acked_count(struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
struct westwood *w = inet_csk_ca(sk);
|
|
|
|
w->cumul_ack = tp->snd_una - w->snd_una;
|
|
|
|
/* If cumul_ack is 0 this is a dupack since it's not moving
|
|
* tp->snd_una.
|
|
*/
|
|
if (!w->cumul_ack) {
|
|
w->accounted += tp->mss_cache;
|
|
w->cumul_ack = tp->mss_cache;
|
|
}
|
|
|
|
if (w->cumul_ack > tp->mss_cache) {
|
|
/* Partial or delayed ack */
|
|
if (w->accounted >= w->cumul_ack) {
|
|
w->accounted -= w->cumul_ack;
|
|
w->cumul_ack = tp->mss_cache;
|
|
} else {
|
|
w->cumul_ack -= w->accounted;
|
|
w->accounted = 0;
|
|
}
|
|
}
|
|
|
|
w->snd_una = tp->snd_una;
|
|
|
|
return w->cumul_ack;
|
|
}
|
|
|
|
|
|
/*
|
|
* TCP Westwood
|
|
* Here limit is evaluated as Bw estimation*RTTmin (for obtaining it
|
|
* in packets we use mss_cache). Rttmin is guaranteed to be >= 2
|
|
* so avoids ever returning 0.
|
|
*/
|
|
static u32 tcp_westwood_bw_rttmin(const struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
const struct westwood *w = inet_csk_ca(sk);
|
|
return max_t(u32, (w->bw_est * w->rtt_min) / tp->mss_cache, 2);
|
|
}
|
|
|
|
static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct westwood *w = inet_csk_ca(sk);
|
|
|
|
switch(event) {
|
|
case CA_EVENT_FAST_ACK:
|
|
westwood_fast_bw(sk);
|
|
break;
|
|
|
|
case CA_EVENT_COMPLETE_CWR:
|
|
tp->snd_cwnd = tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk);
|
|
break;
|
|
|
|
case CA_EVENT_FRTO:
|
|
tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk);
|
|
/* Update RTT_min when next ack arrives */
|
|
w->reset_rtt_min = 1;
|
|
break;
|
|
|
|
case CA_EVENT_SLOW_ACK:
|
|
westwood_update_window(sk);
|
|
w->bk += westwood_acked_count(sk);
|
|
update_rtt_min(w);
|
|
break;
|
|
|
|
default:
|
|
/* don't care */
|
|
break;
|
|
}
|
|
}
|
|
|
|
|
|
/* Extract info for Tcp socket info provided via netlink. */
|
|
static void tcp_westwood_info(struct sock *sk, u32 ext,
|
|
struct sk_buff *skb)
|
|
{
|
|
const struct westwood *ca = inet_csk_ca(sk);
|
|
if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
|
|
struct rtattr *rta;
|
|
struct tcpvegas_info *info;
|
|
|
|
rta = __RTA_PUT(skb, INET_DIAG_VEGASINFO, sizeof(*info));
|
|
info = RTA_DATA(rta);
|
|
info->tcpv_enabled = 1;
|
|
info->tcpv_rttcnt = 0;
|
|
info->tcpv_rtt = jiffies_to_usecs(ca->rtt);
|
|
info->tcpv_minrtt = jiffies_to_usecs(ca->rtt_min);
|
|
rtattr_failure: ;
|
|
}
|
|
}
|
|
|
|
|
|
static struct tcp_congestion_ops tcp_westwood = {
|
|
.init = tcp_westwood_init,
|
|
.ssthresh = tcp_reno_ssthresh,
|
|
.cong_avoid = tcp_reno_cong_avoid,
|
|
.min_cwnd = tcp_westwood_bw_rttmin,
|
|
.cwnd_event = tcp_westwood_event,
|
|
.get_info = tcp_westwood_info,
|
|
.pkts_acked = tcp_westwood_pkts_acked,
|
|
|
|
.owner = THIS_MODULE,
|
|
.name = "westwood"
|
|
};
|
|
|
|
static int __init tcp_westwood_register(void)
|
|
{
|
|
BUILD_BUG_ON(sizeof(struct westwood) > ICSK_CA_PRIV_SIZE);
|
|
return tcp_register_congestion_control(&tcp_westwood);
|
|
}
|
|
|
|
static void __exit tcp_westwood_unregister(void)
|
|
{
|
|
tcp_unregister_congestion_control(&tcp_westwood);
|
|
}
|
|
|
|
module_init(tcp_westwood_register);
|
|
module_exit(tcp_westwood_unregister);
|
|
|
|
MODULE_AUTHOR("Stephen Hemminger, Angelo Dell'Aera");
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_DESCRIPTION("TCP Westwood+");
|