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authorDavid S. Miller <davem@davemloft.net>2006-07-10 17:16:32 -0400
committerDavid S. Miller <davem@sunset.davemloft.net>2006-07-10 17:50:35 -0400
commitc427d27452b41378e305af80db5757da048dd38e (patch)
treed2c07b903b14610e629ee91a163ea01cf4775177 /net/ipv4
parent1eeb7e42888b3bde403596eebdbd64452a53f4d5 (diff)
[TCP]: Remove TCP Compound
This reverts: f890f921040fef6a35e39d15b729af1fd1a35f29 The inclusion of TCP Compound needs to be reverted at this time because it is not 100% certain that this code conforms to the requirements of Developer's Certificate of Origin 1.1 paragraph (b). Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
-rw-r--r--net/ipv4/Kconfig10
-rw-r--r--net/ipv4/Makefile1
-rw-r--r--net/ipv4/tcp_compound.c448
3 files changed, 0 insertions, 459 deletions
diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index da33393be45f..8514106761b0 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -572,16 +572,6 @@ config TCP_CONG_VENO
572 loss packets. 572 loss packets.
573 See http://www.ntu.edu.sg/home5/ZHOU0022/papers/CPFu03a.pdf 573 See http://www.ntu.edu.sg/home5/ZHOU0022/papers/CPFu03a.pdf
574 574
575config TCP_CONG_COMPOUND
576 tristate "TCP Compound"
577 depends on EXPERIMENTAL
578 default n
579 ---help---
580 TCP Compound is a sender-side only change to TCP that uses
581 a mixed Reno/Vegas approach to calculate the cwnd.
582 For further details look here:
583 ftp://ftp.research.microsoft.com/pub/tr/TR-2005-86.pdf
584
585endmenu 575endmenu
586 576
587config TCP_CONG_BIC 577config TCP_CONG_BIC
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index 38b8039bdd55..4878fc5be85f 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -47,7 +47,6 @@ obj-$(CONFIG_TCP_CONG_VEGAS) += tcp_vegas.o
47obj-$(CONFIG_TCP_CONG_VENO) += tcp_veno.o 47obj-$(CONFIG_TCP_CONG_VENO) += tcp_veno.o
48obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o 48obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o
49obj-$(CONFIG_TCP_CONG_LP) += tcp_lp.o 49obj-$(CONFIG_TCP_CONG_LP) += tcp_lp.o
50obj-$(CONFIG_TCP_CONG_COMPOUND) += tcp_compound.o
51 50
52obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \ 51obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
53 xfrm4_output.o 52 xfrm4_output.o
diff --git a/net/ipv4/tcp_compound.c b/net/ipv4/tcp_compound.c
deleted file mode 100644
index bc54f7e9aea9..000000000000
--- a/net/ipv4/tcp_compound.c
+++ /dev/null
@@ -1,448 +0,0 @@
1/*
2 * TCP Vegas congestion control
3 *
4 * This is based on the congestion detection/avoidance scheme described in
5 * Lawrence S. Brakmo and Larry L. Peterson.
6 * "TCP Vegas: End to end congestion avoidance on a global internet."
7 * IEEE Journal on Selected Areas in Communication, 13(8):1465--1480,
8 * October 1995. Available from:
9 * ftp://ftp.cs.arizona.edu/xkernel/Papers/jsac.ps
10 *
11 * See http://www.cs.arizona.edu/xkernel/ for their implementation.
12 * The main aspects that distinguish this implementation from the
13 * Arizona Vegas implementation are:
14 * o We do not change the loss detection or recovery mechanisms of
15 * Linux in any way. Linux already recovers from losses quite well,
16 * using fine-grained timers, NewReno, and FACK.
17 * o To avoid the performance penalty imposed by increasing cwnd
18 * only every-other RTT during slow start, we increase during
19 * every RTT during slow start, just like Reno.
20 * o Largely to allow continuous cwnd growth during slow start,
21 * we use the rate at which ACKs come back as the "actual"
22 * rate, rather than the rate at which data is sent.
23 * o To speed convergence to the right rate, we set the cwnd
24 * to achieve the right ("actual") rate when we exit slow start.
25 * o To filter out the noise caused by delayed ACKs, we use the
26 * minimum RTT sample observed during the last RTT to calculate
27 * the actual rate.
28 * o When the sender re-starts from idle, it waits until it has
29 * received ACKs for an entire flight of new data before making
30 * a cwnd adjustment decision. The original Vegas implementation
31 * assumed senders never went idle.
32 *
33 *
34 * TCP Compound based on TCP Vegas
35 *
36 * further details can be found here:
37 * ftp://ftp.research.microsoft.com/pub/tr/TR-2005-86.pdf
38 */
39
40#include <linux/config.h>
41#include <linux/mm.h>
42#include <linux/module.h>
43#include <linux/skbuff.h>
44#include <linux/inet_diag.h>
45
46#include <net/tcp.h>
47
48/* Default values of the Vegas variables, in fixed-point representation
49 * with V_PARAM_SHIFT bits to the right of the binary point.
50 */
51#define V_PARAM_SHIFT 1
52
53#define TCP_COMPOUND_ALPHA 3U
54#define TCP_COMPOUND_BETA 1U
55#define TCP_COMPOUND_GAMMA 30
56#define TCP_COMPOUND_ZETA 1
57
58/* TCP compound variables */
59struct compound {
60 u32 beg_snd_nxt; /* right edge during last RTT */
61 u32 beg_snd_una; /* left edge during last RTT */
62 u32 beg_snd_cwnd; /* saves the size of the cwnd */
63 u8 doing_vegas_now; /* if true, do vegas for this RTT */
64 u16 cntRTT; /* # of RTTs measured within last RTT */
65 u32 minRTT; /* min of RTTs measured within last RTT (in usec) */
66 u32 baseRTT; /* the min of all Vegas RTT measurements seen (in usec) */
67
68 u32 cwnd;
69 u32 dwnd;
70};
71
72/* There are several situations when we must "re-start" Vegas:
73 *
74 * o when a connection is established
75 * o after an RTO
76 * o after fast recovery
77 * o when we send a packet and there is no outstanding
78 * unacknowledged data (restarting an idle connection)
79 *
80 * In these circumstances we cannot do a Vegas calculation at the
81 * end of the first RTT, because any calculation we do is using
82 * stale info -- both the saved cwnd and congestion feedback are
83 * stale.
84 *
85 * Instead we must wait until the completion of an RTT during
86 * which we actually receive ACKs.
87 */
88static inline void vegas_enable(struct sock *sk)
89{
90 const struct tcp_sock *tp = tcp_sk(sk);
91 struct compound *vegas = inet_csk_ca(sk);
92
93 /* Begin taking Vegas samples next time we send something. */
94 vegas->doing_vegas_now = 1;
95
96 /* Set the beginning of the next send window. */
97 vegas->beg_snd_nxt = tp->snd_nxt;
98
99 vegas->cntRTT = 0;
100 vegas->minRTT = 0x7fffffff;
101}
102
103/* Stop taking Vegas samples for now. */
104static inline void vegas_disable(struct sock *sk)
105{
106 struct compound *vegas = inet_csk_ca(sk);
107
108 vegas->doing_vegas_now = 0;
109}
110
111static void tcp_compound_init(struct sock *sk)
112{
113 struct compound *vegas = inet_csk_ca(sk);
114 const struct tcp_sock *tp = tcp_sk(sk);
115
116 vegas->baseRTT = 0x7fffffff;
117 vegas_enable(sk);
118
119 vegas->dwnd = 0;
120 vegas->cwnd = tp->snd_cwnd;
121}
122
123/* Do RTT sampling needed for Vegas.
124 * Basically we:
125 * o min-filter RTT samples from within an RTT to get the current
126 * propagation delay + queuing delay (we are min-filtering to try to
127 * avoid the effects of delayed ACKs)
128 * o min-filter RTT samples from a much longer window (forever for now)
129 * to find the propagation delay (baseRTT)
130 */
131static void tcp_compound_rtt_calc(struct sock *sk, u32 usrtt)
132{
133 struct compound *vegas = inet_csk_ca(sk);
134 u32 vrtt = usrtt + 1; /* Never allow zero rtt or baseRTT */
135
136 /* Filter to find propagation delay: */
137 if (vrtt < vegas->baseRTT)
138 vegas->baseRTT = vrtt;
139
140 /* Find the min RTT during the last RTT to find
141 * the current prop. delay + queuing delay:
142 */
143
144 vegas->minRTT = min(vegas->minRTT, vrtt);
145 vegas->cntRTT++;
146}
147
148static void tcp_compound_state(struct sock *sk, u8 ca_state)
149{
150
151 if (ca_state == TCP_CA_Open)
152 vegas_enable(sk);
153 else
154 vegas_disable(sk);
155}
156
157
158/* 64bit divisor, dividend and result. dynamic precision */
159static inline u64 div64_64(u64 dividend, u64 divisor)
160{
161 u32 d = divisor;
162
163 if (divisor > 0xffffffffULL) {
164 unsigned int shift = fls(divisor >> 32);
165
166 d = divisor >> shift;
167 dividend >>= shift;
168 }
169
170 /* avoid 64 bit division if possible */
171 if (dividend >> 32)
172 do_div(dividend, d);
173 else
174 dividend = (u32) dividend / d;
175
176 return dividend;
177}
178
179/* calculate the quartic root of "a" using Newton-Raphson */
180static u32 qroot(u64 a)
181{
182 u32 x, x1;
183
184 /* Initial estimate is based on:
185 * qrt(x) = exp(log(x) / 4)
186 */
187 x = 1u << (fls64(a) >> 2);
188
189 /*
190 * Iteration based on:
191 * 3
192 * x = ( 3 * x + a / x ) / 4
193 * k+1 k k
194 */
195 do {
196 u64 x3 = x;
197
198 x1 = x;
199 x3 *= x;
200 x3 *= x;
201
202 x = (3 * x + (u32) div64_64(a, x3)) / 4;
203 } while (abs(x1 - x) > 1);
204
205 return x;
206}
207
208
209/*
210 * If the connection is idle and we are restarting,
211 * then we don't want to do any Vegas calculations
212 * until we get fresh RTT samples. So when we
213 * restart, we reset our Vegas state to a clean
214 * slate. After we get acks for this flight of
215 * packets, _then_ we can make Vegas calculations
216 * again.
217 */
218static void tcp_compound_cwnd_event(struct sock *sk, enum tcp_ca_event event)
219{
220 if (event == CA_EVENT_CWND_RESTART || event == CA_EVENT_TX_START)
221 tcp_compound_init(sk);
222}
223
224static void tcp_compound_cong_avoid(struct sock *sk, u32 ack,
225 u32 seq_rtt, u32 in_flight, int flag)
226{
227 struct tcp_sock *tp = tcp_sk(sk);
228 struct compound *vegas = inet_csk_ca(sk);
229 u8 inc = 0;
230
231 if (vegas->cwnd + vegas->dwnd > tp->snd_cwnd) {
232 if (vegas->cwnd > tp->snd_cwnd || vegas->dwnd > tp->snd_cwnd) {
233 vegas->cwnd = tp->snd_cwnd;
234 vegas->dwnd = 0;
235 } else
236 vegas->cwnd = tp->snd_cwnd - vegas->dwnd;
237
238 }
239
240 if (!tcp_is_cwnd_limited(sk, in_flight))
241 return;
242
243 if (vegas->cwnd <= tp->snd_ssthresh)
244 inc = 1;
245 else if (tp->snd_cwnd_cnt < tp->snd_cwnd)
246 tp->snd_cwnd_cnt++;
247
248 if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
249 inc = 1;
250 tp->snd_cwnd_cnt = 0;
251 }
252
253 if (inc && tp->snd_cwnd < tp->snd_cwnd_clamp)
254 vegas->cwnd++;
255
256 /* The key players are v_beg_snd_una and v_beg_snd_nxt.
257 *
258 * These are so named because they represent the approximate values
259 * of snd_una and snd_nxt at the beginning of the current RTT. More
260 * precisely, they represent the amount of data sent during the RTT.
261 * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
262 * we will calculate that (v_beg_snd_nxt - v_beg_snd_una) outstanding
263 * bytes of data have been ACKed during the course of the RTT, giving
264 * an "actual" rate of:
265 *
266 * (v_beg_snd_nxt - v_beg_snd_una) / (rtt duration)
267 *
268 * Unfortunately, v_beg_snd_una is not exactly equal to snd_una,
269 * because delayed ACKs can cover more than one segment, so they
270 * don't line up nicely with the boundaries of RTTs.
271 *
272 * Another unfortunate fact of life is that delayed ACKs delay the
273 * advance of the left edge of our send window, so that the number
274 * of bytes we send in an RTT is often less than our cwnd will allow.
275 * So we keep track of our cwnd separately, in v_beg_snd_cwnd.
276 */
277
278 if (after(ack, vegas->beg_snd_nxt)) {
279 /* Do the Vegas once-per-RTT cwnd adjustment. */
280 u32 old_wnd, old_snd_cwnd;
281
282 /* Here old_wnd is essentially the window of data that was
283 * sent during the previous RTT, and has all
284 * been acknowledged in the course of the RTT that ended
285 * with the ACK we just received. Likewise, old_snd_cwnd
286 * is the cwnd during the previous RTT.
287 */
288 if (!tp->mss_cache)
289 return;
290
291 old_wnd = (vegas->beg_snd_nxt - vegas->beg_snd_una) /
292 tp->mss_cache;
293 old_snd_cwnd = vegas->beg_snd_cwnd;
294
295 /* Save the extent of the current window so we can use this
296 * at the end of the next RTT.
297 */
298 vegas->beg_snd_una = vegas->beg_snd_nxt;
299 vegas->beg_snd_nxt = tp->snd_nxt;
300 vegas->beg_snd_cwnd = tp->snd_cwnd;
301
302 /* We do the Vegas calculations only if we got enough RTT
303 * samples that we can be reasonably sure that we got
304 * at least one RTT sample that wasn't from a delayed ACK.
305 * If we only had 2 samples total,
306 * then that means we're getting only 1 ACK per RTT, which
307 * means they're almost certainly delayed ACKs.
308 * If we have 3 samples, we should be OK.
309 */
310
311 if (vegas->cntRTT > 2) {
312 u32 rtt, target_cwnd, diff;
313 u32 brtt, dwnd;
314
315 /* We have enough RTT samples, so, using the Vegas
316 * algorithm, we determine if we should increase or
317 * decrease cwnd, and by how much.
318 */
319
320 /* Pluck out the RTT we are using for the Vegas
321 * calculations. This is the min RTT seen during the
322 * last RTT. Taking the min filters out the effects
323 * of delayed ACKs, at the cost of noticing congestion
324 * a bit later.
325 */
326 rtt = vegas->minRTT;
327
328 /* Calculate the cwnd we should have, if we weren't
329 * going too fast.
330 *
331 * This is:
332 * (actual rate in segments) * baseRTT
333 * We keep it as a fixed point number with
334 * V_PARAM_SHIFT bits to the right of the binary point.
335 */
336 if (!rtt)
337 return;
338
339 brtt = vegas->baseRTT;
340 target_cwnd = ((old_wnd * brtt)
341 << V_PARAM_SHIFT) / rtt;
342
343 /* Calculate the difference between the window we had,
344 * and the window we would like to have. This quantity
345 * is the "Diff" from the Arizona Vegas papers.
346 *
347 * Again, this is a fixed point number with
348 * V_PARAM_SHIFT bits to the right of the binary
349 * point.
350 */
351
352 diff = (old_wnd << V_PARAM_SHIFT) - target_cwnd;
353
354 dwnd = vegas->dwnd;
355
356 if (diff < (TCP_COMPOUND_GAMMA << V_PARAM_SHIFT)) {
357 u64 v;
358 u32 x;
359
360 /*
361 * The TCP Compound paper describes the choice
362 * of "k" determines the agressiveness,
363 * ie. slope of the response function.
364 *
365 * For same value as HSTCP would be 0.8
366 * but for computaional reasons, both the
367 * original authors and this implementation
368 * use 0.75.
369 */
370 v = old_wnd;
371 x = qroot(v * v * v) >> TCP_COMPOUND_ALPHA;
372 if (x > 1)
373 dwnd = x - 1;
374 else
375 dwnd = 0;
376
377 dwnd += vegas->dwnd;
378
379 } else if ((dwnd << V_PARAM_SHIFT) <
380 (diff * TCP_COMPOUND_BETA))
381 dwnd = 0;
382 else
383 dwnd =
384 ((dwnd << V_PARAM_SHIFT) -
385 (diff *
386 TCP_COMPOUND_BETA)) >> V_PARAM_SHIFT;
387
388 vegas->dwnd = dwnd;
389
390 }
391
392 /* Wipe the slate clean for the next RTT. */
393 vegas->cntRTT = 0;
394 vegas->minRTT = 0x7fffffff;
395 }
396
397 tp->snd_cwnd = vegas->cwnd + vegas->dwnd;
398}
399
400/* Extract info for Tcp socket info provided via netlink. */
401static void tcp_compound_get_info(struct sock *sk, u32 ext, struct sk_buff *skb)
402{
403 const struct compound *ca = inet_csk_ca(sk);
404 if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
405 struct tcpvegas_info *info;
406
407 info = RTA_DATA(__RTA_PUT(skb, INET_DIAG_VEGASINFO,
408 sizeof(*info)));
409
410 info->tcpv_enabled = ca->doing_vegas_now;
411 info->tcpv_rttcnt = ca->cntRTT;
412 info->tcpv_rtt = ca->baseRTT;
413 info->tcpv_minrtt = ca->minRTT;
414 rtattr_failure:;
415 }
416}
417
418static struct tcp_congestion_ops tcp_compound = {
419 .init = tcp_compound_init,
420 .ssthresh = tcp_reno_ssthresh,
421 .cong_avoid = tcp_compound_cong_avoid,
422 .rtt_sample = tcp_compound_rtt_calc,
423 .set_state = tcp_compound_state,
424 .cwnd_event = tcp_compound_cwnd_event,
425 .get_info = tcp_compound_get_info,
426
427 .owner = THIS_MODULE,
428 .name = "compound",
429};
430
431static int __init tcp_compound_register(void)
432{
433 BUG_ON(sizeof(struct compound) > ICSK_CA_PRIV_SIZE);
434 tcp_register_congestion_control(&tcp_compound);
435 return 0;
436}
437
438static void __exit tcp_compound_unregister(void)
439{
440 tcp_unregister_congestion_control(&tcp_compound);
441}
442
443module_init(tcp_compound_register);
444module_exit(tcp_compound_unregister);
445
446MODULE_AUTHOR("Angelo P. Castellani, Stephen Hemminger");
447MODULE_LICENSE("GPL");
448MODULE_DESCRIPTION("TCP Compound");
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