Blame view
net/ipv4/tcp_westwood.c
8.24 KB
872707628 [TCP]: Add TCP We... |
1 |
/* |
b7d7a9e3c [TCP] Westwood: c... |
2 |
* TCP Westwood+: end-to-end bandwidth estimation for TCP |
872707628 [TCP]: Add TCP We... |
3 |
* |
b7d7a9e3c [TCP] Westwood: c... |
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 |
* 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. |
872707628 [TCP]: Add TCP We... |
22 |
*/ |
872707628 [TCP]: Add TCP We... |
23 24 25 |
#include <linux/mm.h> #include <linux/module.h> #include <linux/skbuff.h> |
a8c2190ee [INET_DIAG]: Rena... |
26 |
#include <linux/inet_diag.h> |
872707628 [TCP]: Add TCP We... |
27 28 29 30 31 32 33 34 35 36 37 38 39 |
#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 */ |
f61e29018 [TCP] Westwood: f... |
40 |
u8 first_ack; /* flag which infers that this is the first ack */ |
bc726a71d [TCP] Westwood: r... |
41 |
u8 reset_rtt_min; /* Reset RTT min to next RTT sample*/ |
872707628 [TCP]: Add TCP We... |
42 |
}; |
872707628 [TCP]: Add TCP We... |
43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 |
/* 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. */ |
6687e988d [ICSK]: Move TCP ... |
58 |
static void tcp_westwood_init(struct sock *sk) |
872707628 [TCP]: Add TCP We... |
59 |
{ |
6687e988d [ICSK]: Move TCP ... |
60 |
struct westwood *w = inet_csk_ca(sk); |
872707628 [TCP]: Add TCP We... |
61 62 |
w->bk = 0; |
e905a9eda [NET] IPV4: Fix w... |
63 64 65 66 |
w->bw_ns_est = 0; w->bw_est = 0; w->accounted = 0; w->cumul_ack = 0; |
bc726a71d [TCP] Westwood: r... |
67 |
w->reset_rtt_min = 1; |
872707628 [TCP]: Add TCP We... |
68 |
w->rtt_min = w->rtt = TCP_WESTWOOD_INIT_RTT; |
ad5ad69e6 tcp_westwood: use... |
69 |
w->rtt_win_sx = tcp_jiffies32; |
6687e988d [ICSK]: Move TCP ... |
70 |
w->snd_una = tcp_sk(sk)->snd_una; |
f61e29018 [TCP] Westwood: f... |
71 |
w->first_ack = 1; |
872707628 [TCP]: Add TCP We... |
72 73 74 75 76 77 78 79 |
} /* * @westwood_do_filter * Low-pass filter. Implemented using constant coefficients. */ static inline u32 westwood_do_filter(u32 a, u32 b) { |
a02cec215 net: return opera... |
80 |
return ((7 * a) + b) >> 3; |
872707628 [TCP]: Add TCP We... |
81 |
} |
b3a92eabe [TCP] Westwood: b... |
82 |
static void westwood_filter(struct westwood *w, u32 delta) |
872707628 [TCP]: Add TCP We... |
83 |
{ |
b3a92eabe [TCP] Westwood: b... |
84 85 86 87 88 89 90 91 |
/* 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); } |
872707628 [TCP]: Add TCP We... |
92 93 94 95 96 97 98 |
} /* * @westwood_pkts_acked * Called after processing group of packets. * but all westwood needs is the last sample of srtt. */ |
756ee1729 tcp: replace cnt ... |
99 100 |
static void tcp_westwood_pkts_acked(struct sock *sk, const struct ack_sample *sample) |
872707628 [TCP]: Add TCP We... |
101 |
{ |
6687e988d [ICSK]: Move TCP ... |
102 |
struct westwood *w = inet_csk_ca(sk); |
30cfd0baf [TCP]: congestion... |
103 |
|
756ee1729 tcp: replace cnt ... |
104 105 |
if (sample->rtt_us > 0) w->rtt = usecs_to_jiffies(sample->rtt_us); |
872707628 [TCP]: Add TCP We... |
106 107 108 109 110 111 112 |
} /* * @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. */ |
6687e988d [ICSK]: Move TCP ... |
113 |
static void westwood_update_window(struct sock *sk) |
872707628 [TCP]: Add TCP We... |
114 |
{ |
6687e988d [ICSK]: Move TCP ... |
115 |
struct westwood *w = inet_csk_ca(sk); |
ad5ad69e6 tcp_westwood: use... |
116 |
s32 delta = tcp_jiffies32 - w->rtt_win_sx; |
872707628 [TCP]: Add TCP We... |
117 |
|
b7d7a9e3c [TCP] Westwood: c... |
118 |
/* Initialize w->snd_una with the first acked sequence number in order |
f61e29018 [TCP] Westwood: f... |
119 120 121 |
* to fix mismatch between tp->snd_una and w->snd_una for the first * bandwidth sample */ |
e905a9eda [NET] IPV4: Fix w... |
122 |
if (w->first_ack) { |
f61e29018 [TCP] Westwood: f... |
123 124 125 |
w->snd_una = tcp_sk(sk)->snd_una; w->first_ack = 0; } |
872707628 [TCP]: Add TCP We... |
126 127 128 129 130 131 132 133 134 135 136 137 138 |
/* * 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; |
ad5ad69e6 tcp_westwood: use... |
139 |
w->rtt_win_sx = tcp_jiffies32; |
872707628 [TCP]: Add TCP We... |
140 141 |
} } |
bc726a71d [TCP] Westwood: r... |
142 143 144 145 |
static inline void update_rtt_min(struct westwood *w) { if (w->reset_rtt_min) { w->rtt_min = w->rtt; |
e905a9eda [NET] IPV4: Fix w... |
146 |
w->reset_rtt_min = 0; |
bc726a71d [TCP] Westwood: r... |
147 148 149 |
} else w->rtt_min = min(w->rtt, w->rtt_min); } |
872707628 [TCP]: Add TCP We... |
150 151 152 153 154 155 |
/* * @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. */ |
6687e988d [ICSK]: Move TCP ... |
156 |
static inline void westwood_fast_bw(struct sock *sk) |
872707628 [TCP]: Add TCP We... |
157 |
{ |
6687e988d [ICSK]: Move TCP ... |
158 159 |
const struct tcp_sock *tp = tcp_sk(sk); struct westwood *w = inet_csk_ca(sk); |
872707628 [TCP]: Add TCP We... |
160 |
|
6687e988d [ICSK]: Move TCP ... |
161 |
westwood_update_window(sk); |
872707628 [TCP]: Add TCP We... |
162 163 164 |
w->bk += tp->snd_una - w->snd_una; w->snd_una = tp->snd_una; |
bc726a71d [TCP] Westwood: r... |
165 |
update_rtt_min(w); |
872707628 [TCP]: Add TCP We... |
166 167 168 169 170 171 172 |
} /* * @westwood_acked_count * This function evaluates cumul_ack for evaluating bk in case of * delayed or partial acks. */ |
6687e988d [ICSK]: Move TCP ... |
173 |
static inline u32 westwood_acked_count(struct sock *sk) |
872707628 [TCP]: Add TCP We... |
174 |
{ |
6687e988d [ICSK]: Move TCP ... |
175 176 |
const struct tcp_sock *tp = tcp_sk(sk); struct westwood *w = inet_csk_ca(sk); |
872707628 [TCP]: Add TCP We... |
177 178 |
w->cumul_ack = tp->snd_una - w->snd_una; |
e905a9eda [NET] IPV4: Fix w... |
179 180 181 182 |
/* If cumul_ack is 0 this is a dupack since it's not moving * tp->snd_una. */ if (!w->cumul_ack) { |
872707628 [TCP]: Add TCP We... |
183 184 185 |
w->accounted += tp->mss_cache; w->cumul_ack = tp->mss_cache; } |
e905a9eda [NET] IPV4: Fix w... |
186 |
if (w->cumul_ack > tp->mss_cache) { |
872707628 [TCP]: Add TCP We... |
187 188 189 190 191 192 193 194 195 196 197 198 199 200 |
/* 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; } |
872707628 [TCP]: Add TCP We... |
201 202 203 204 205 206 |
/* * 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. */ |
72dc5b922 [TCP]: Minimum co... |
207 |
static u32 tcp_westwood_bw_rttmin(const struct sock *sk) |
872707628 [TCP]: Add TCP We... |
208 |
{ |
72dc5b922 [TCP]: Minimum co... |
209 210 |
const struct tcp_sock *tp = tcp_sk(sk); const struct westwood *w = inet_csk_ca(sk); |
688d1945b tcp: whitespace f... |
211 |
|
72dc5b922 [TCP]: Minimum co... |
212 |
return max_t(u32, (w->bw_est * w->rtt_min) / tp->mss_cache, 2); |
872707628 [TCP]: Add TCP We... |
213 |
} |
7354c8c38 net: tcp: split a... |
214 215 216 217 218 219 220 221 222 223 224 225 226 227 |
static void tcp_westwood_ack(struct sock *sk, u32 ack_flags) { if (ack_flags & CA_ACK_SLOWPATH) { struct westwood *w = inet_csk_ca(sk); westwood_update_window(sk); w->bk += westwood_acked_count(sk); update_rtt_min(w); return; } westwood_fast_bw(sk); } |
6687e988d [ICSK]: Move TCP ... |
228 |
static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event) |
872707628 [TCP]: Add TCP We... |
229 |
{ |
6687e988d [ICSK]: Move TCP ... |
230 231 |
struct tcp_sock *tp = tcp_sk(sk); struct westwood *w = inet_csk_ca(sk); |
b7d7a9e3c [TCP] Westwood: c... |
232 |
|
2de979bd7 [TCP]: whitespace... |
233 |
switch (event) { |
872707628 [TCP]: Add TCP We... |
234 |
case CA_EVENT_COMPLETE_CWR: |
72dc5b922 [TCP]: Minimum co... |
235 |
tp->snd_cwnd = tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk); |
872707628 [TCP]: Add TCP We... |
236 |
break; |
9b44190dc tcp: refactor F-RTO |
237 |
case CA_EVENT_LOSS: |
72dc5b922 [TCP]: Minimum co... |
238 |
tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk); |
e905a9eda [NET] IPV4: Fix w... |
239 |
/* Update RTT_min when next ack arrives */ |
bc726a71d [TCP] Westwood: r... |
240 |
w->reset_rtt_min = 1; |
872707628 [TCP]: Add TCP We... |
241 |
break; |
872707628 [TCP]: Add TCP We... |
242 243 244 245 246 |
default: /* don't care */ break; } } |
872707628 [TCP]: Add TCP We... |
247 |
/* Extract info for Tcp socket info provided via netlink. */ |
31ccd0e66 tcp_westwood: fix... |
248 249 |
static size_t tcp_westwood_info(struct sock *sk, u32 ext, int *attr, union tcp_cc_info *info) |
872707628 [TCP]: Add TCP We... |
250 |
{ |
6687e988d [ICSK]: Move TCP ... |
251 |
const struct westwood *ca = inet_csk_ca(sk); |
688d1945b tcp: whitespace f... |
252 |
|
73c1f4a03 [TCPDIAG]: Just r... |
253 |
if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) { |
31ccd0e66 tcp_westwood: fix... |
254 255 |
info->vegas.tcpv_enabled = 1; info->vegas.tcpv_rttcnt = 0; |
be7164cd5 tcp_westwood: fix... |
256 257 |
info->vegas.tcpv_rtt = jiffies_to_usecs(ca->rtt); info->vegas.tcpv_minrtt = jiffies_to_usecs(ca->rtt_min); |
267281058 [TCP] westwood: U... |
258 |
|
31ccd0e66 tcp_westwood: fix... |
259 260 |
*attr = INET_DIAG_VEGASINFO; return sizeof(struct tcpvegas_info); |
872707628 [TCP]: Add TCP We... |
261 |
} |
521f1cf1d inet_diag: fix ac... |
262 |
return 0; |
872707628 [TCP]: Add TCP We... |
263 |
} |
a252bebe2 tcp: mark tcp_con... |
264 |
static struct tcp_congestion_ops tcp_westwood __read_mostly = { |
872707628 [TCP]: Add TCP We... |
265 266 267 |
.init = tcp_westwood_init, .ssthresh = tcp_reno_ssthresh, .cong_avoid = tcp_reno_cong_avoid, |
e97991832 tcp: make undo_cw... |
268 |
.undo_cwnd = tcp_reno_undo_cwnd, |
872707628 [TCP]: Add TCP We... |
269 |
.cwnd_event = tcp_westwood_event, |
7354c8c38 net: tcp: split a... |
270 |
.in_ack_event = tcp_westwood_ack, |
872707628 [TCP]: Add TCP We... |
271 272 273 274 275 276 277 278 279 |
.get_info = tcp_westwood_info, .pkts_acked = tcp_westwood_pkts_acked, .owner = THIS_MODULE, .name = "westwood" }; static int __init tcp_westwood_register(void) { |
74975d40b [TCP] Congestion ... |
280 |
BUILD_BUG_ON(sizeof(struct westwood) > ICSK_CA_PRIV_SIZE); |
872707628 [TCP]: Add TCP We... |
281 282 283 284 285 286 287 288 289 290 291 292 293 294 |
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+"); |