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1da177e4 LT |
1 | /* |
2 | * net/sched/sch_sfq.c Stochastic Fairness Queueing discipline. | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU General Public License | |
6 | * as published by the Free Software Foundation; either version | |
7 | * 2 of the License, or (at your option) any later version. | |
8 | * | |
9 | * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru> | |
10 | */ | |
11 | ||
1da177e4 | 12 | #include <linux/module.h> |
1da177e4 LT |
13 | #include <linux/types.h> |
14 | #include <linux/kernel.h> | |
15 | #include <linux/jiffies.h> | |
16 | #include <linux/string.h> | |
1da177e4 LT |
17 | #include <linux/in.h> |
18 | #include <linux/errno.h> | |
1da177e4 | 19 | #include <linux/init.h> |
1da177e4 | 20 | #include <linux/ipv6.h> |
1da177e4 | 21 | #include <linux/skbuff.h> |
32740ddc | 22 | #include <linux/jhash.h> |
0ba48053 PM |
23 | #include <net/ip.h> |
24 | #include <net/netlink.h> | |
1da177e4 LT |
25 | #include <net/pkt_sched.h> |
26 | ||
27 | ||
28 | /* Stochastic Fairness Queuing algorithm. | |
29 | ======================================= | |
30 | ||
31 | Source: | |
32 | Paul E. McKenney "Stochastic Fairness Queuing", | |
33 | IEEE INFOCOMM'90 Proceedings, San Francisco, 1990. | |
34 | ||
35 | Paul E. McKenney "Stochastic Fairness Queuing", | |
36 | "Interworking: Research and Experience", v.2, 1991, p.113-131. | |
37 | ||
38 | ||
39 | See also: | |
40 | M. Shreedhar and George Varghese "Efficient Fair | |
41 | Queuing using Deficit Round Robin", Proc. SIGCOMM 95. | |
42 | ||
43 | ||
10297b99 | 44 | This is not the thing that is usually called (W)FQ nowadays. |
1da177e4 LT |
45 | It does not use any timestamp mechanism, but instead |
46 | processes queues in round-robin order. | |
47 | ||
48 | ADVANTAGE: | |
49 | ||
50 | - It is very cheap. Both CPU and memory requirements are minimal. | |
51 | ||
52 | DRAWBACKS: | |
53 | ||
10297b99 | 54 | - "Stochastic" -> It is not 100% fair. |
1da177e4 LT |
55 | When hash collisions occur, several flows are considered as one. |
56 | ||
57 | - "Round-robin" -> It introduces larger delays than virtual clock | |
58 | based schemes, and should not be used for isolating interactive | |
59 | traffic from non-interactive. It means, that this scheduler | |
60 | should be used as leaf of CBQ or P3, which put interactive traffic | |
61 | to higher priority band. | |
62 | ||
63 | We still need true WFQ for top level CSZ, but using WFQ | |
64 | for the best effort traffic is absolutely pointless: | |
65 | SFQ is superior for this purpose. | |
66 | ||
67 | IMPLEMENTATION: | |
68 | This implementation limits maximal queue length to 128; | |
69 | maximal mtu to 2^15-1; number of hash buckets to 1024. | |
70 | The only goal of this restrictions was that all data | |
71 | fit into one 4K page :-). Struct sfq_sched_data is | |
72 | organized in anti-cache manner: all the data for a bucket | |
73 | are scattered over different locations. This is not good, | |
74 | but it allowed me to put it into 4K. | |
75 | ||
76 | It is easy to increase these values, but not in flight. */ | |
77 | ||
78 | #define SFQ_DEPTH 128 | |
79 | #define SFQ_HASH_DIVISOR 1024 | |
80 | ||
81 | /* This type should contain at least SFQ_DEPTH*2 values */ | |
82 | typedef unsigned char sfq_index; | |
83 | ||
84 | struct sfq_head | |
85 | { | |
86 | sfq_index next; | |
87 | sfq_index prev; | |
88 | }; | |
89 | ||
90 | struct sfq_sched_data | |
91 | { | |
92 | /* Parameters */ | |
93 | int perturb_period; | |
94 | unsigned quantum; /* Allotment per round: MUST BE >= MTU */ | |
95 | int limit; | |
96 | ||
97 | /* Variables */ | |
98 | struct timer_list perturb_timer; | |
32740ddc | 99 | u32 perturbation; |
1da177e4 LT |
100 | sfq_index tail; /* Index of current slot in round */ |
101 | sfq_index max_depth; /* Maximal depth */ | |
102 | ||
103 | sfq_index ht[SFQ_HASH_DIVISOR]; /* Hash table */ | |
104 | sfq_index next[SFQ_DEPTH]; /* Active slots link */ | |
105 | short allot[SFQ_DEPTH]; /* Current allotment per slot */ | |
106 | unsigned short hash[SFQ_DEPTH]; /* Hash value indexed by slots */ | |
107 | struct sk_buff_head qs[SFQ_DEPTH]; /* Slot queue */ | |
108 | struct sfq_head dep[SFQ_DEPTH*2]; /* Linked list of slots, indexed by depth */ | |
109 | }; | |
110 | ||
111 | static __inline__ unsigned sfq_fold_hash(struct sfq_sched_data *q, u32 h, u32 h1) | |
112 | { | |
32740ddc | 113 | return jhash_2words(h, h1, q->perturbation) & (SFQ_HASH_DIVISOR - 1); |
1da177e4 LT |
114 | } |
115 | ||
116 | static unsigned sfq_hash(struct sfq_sched_data *q, struct sk_buff *skb) | |
117 | { | |
118 | u32 h, h2; | |
119 | ||
120 | switch (skb->protocol) { | |
121 | case __constant_htons(ETH_P_IP): | |
122 | { | |
eddc9ec5 | 123 | const struct iphdr *iph = ip_hdr(skb); |
1da177e4 LT |
124 | h = iph->daddr; |
125 | h2 = iph->saddr^iph->protocol; | |
126 | if (!(iph->frag_off&htons(IP_MF|IP_OFFSET)) && | |
127 | (iph->protocol == IPPROTO_TCP || | |
128 | iph->protocol == IPPROTO_UDP || | |
a8d0f952 | 129 | iph->protocol == IPPROTO_UDPLITE || |
ae82af54 PM |
130 | iph->protocol == IPPROTO_SCTP || |
131 | iph->protocol == IPPROTO_DCCP || | |
1da177e4 LT |
132 | iph->protocol == IPPROTO_ESP)) |
133 | h2 ^= *(((u32*)iph) + iph->ihl); | |
134 | break; | |
135 | } | |
136 | case __constant_htons(ETH_P_IPV6): | |
137 | { | |
0660e03f | 138 | struct ipv6hdr *iph = ipv6_hdr(skb); |
1da177e4 LT |
139 | h = iph->daddr.s6_addr32[3]; |
140 | h2 = iph->saddr.s6_addr32[3]^iph->nexthdr; | |
141 | if (iph->nexthdr == IPPROTO_TCP || | |
142 | iph->nexthdr == IPPROTO_UDP || | |
a8d0f952 | 143 | iph->nexthdr == IPPROTO_UDPLITE || |
ae82af54 PM |
144 | iph->nexthdr == IPPROTO_SCTP || |
145 | iph->nexthdr == IPPROTO_DCCP || | |
1da177e4 LT |
146 | iph->nexthdr == IPPROTO_ESP) |
147 | h2 ^= *(u32*)&iph[1]; | |
148 | break; | |
149 | } | |
150 | default: | |
151 | h = (u32)(unsigned long)skb->dst^skb->protocol; | |
152 | h2 = (u32)(unsigned long)skb->sk; | |
153 | } | |
154 | return sfq_fold_hash(q, h, h2); | |
155 | } | |
156 | ||
157 | static inline void sfq_link(struct sfq_sched_data *q, sfq_index x) | |
158 | { | |
159 | sfq_index p, n; | |
160 | int d = q->qs[x].qlen + SFQ_DEPTH; | |
161 | ||
162 | p = d; | |
163 | n = q->dep[d].next; | |
164 | q->dep[x].next = n; | |
165 | q->dep[x].prev = p; | |
166 | q->dep[p].next = q->dep[n].prev = x; | |
167 | } | |
168 | ||
169 | static inline void sfq_dec(struct sfq_sched_data *q, sfq_index x) | |
170 | { | |
171 | sfq_index p, n; | |
172 | ||
173 | n = q->dep[x].next; | |
174 | p = q->dep[x].prev; | |
175 | q->dep[p].next = n; | |
176 | q->dep[n].prev = p; | |
177 | ||
178 | if (n == p && q->max_depth == q->qs[x].qlen + 1) | |
179 | q->max_depth--; | |
180 | ||
181 | sfq_link(q, x); | |
182 | } | |
183 | ||
184 | static inline void sfq_inc(struct sfq_sched_data *q, sfq_index x) | |
185 | { | |
186 | sfq_index p, n; | |
187 | int d; | |
188 | ||
189 | n = q->dep[x].next; | |
190 | p = q->dep[x].prev; | |
191 | q->dep[p].next = n; | |
192 | q->dep[n].prev = p; | |
193 | d = q->qs[x].qlen; | |
194 | if (q->max_depth < d) | |
195 | q->max_depth = d; | |
196 | ||
197 | sfq_link(q, x); | |
198 | } | |
199 | ||
200 | static unsigned int sfq_drop(struct Qdisc *sch) | |
201 | { | |
202 | struct sfq_sched_data *q = qdisc_priv(sch); | |
203 | sfq_index d = q->max_depth; | |
204 | struct sk_buff *skb; | |
205 | unsigned int len; | |
206 | ||
207 | /* Queue is full! Find the longest slot and | |
208 | drop a packet from it */ | |
209 | ||
210 | if (d > 1) { | |
211 | sfq_index x = q->dep[d+SFQ_DEPTH].next; | |
212 | skb = q->qs[x].prev; | |
213 | len = skb->len; | |
214 | __skb_unlink(skb, &q->qs[x]); | |
215 | kfree_skb(skb); | |
216 | sfq_dec(q, x); | |
217 | sch->q.qlen--; | |
218 | sch->qstats.drops++; | |
f5539eb8 | 219 | sch->qstats.backlog -= len; |
1da177e4 LT |
220 | return len; |
221 | } | |
222 | ||
223 | if (d == 1) { | |
224 | /* It is difficult to believe, but ALL THE SLOTS HAVE LENGTH 1. */ | |
225 | d = q->next[q->tail]; | |
226 | q->next[q->tail] = q->next[d]; | |
227 | q->allot[q->next[d]] += q->quantum; | |
228 | skb = q->qs[d].prev; | |
229 | len = skb->len; | |
230 | __skb_unlink(skb, &q->qs[d]); | |
231 | kfree_skb(skb); | |
232 | sfq_dec(q, d); | |
233 | sch->q.qlen--; | |
234 | q->ht[q->hash[d]] = SFQ_DEPTH; | |
235 | sch->qstats.drops++; | |
f5539eb8 | 236 | sch->qstats.backlog -= len; |
1da177e4 LT |
237 | return len; |
238 | } | |
239 | ||
240 | return 0; | |
241 | } | |
242 | ||
243 | static int | |
244 | sfq_enqueue(struct sk_buff *skb, struct Qdisc* sch) | |
245 | { | |
246 | struct sfq_sched_data *q = qdisc_priv(sch); | |
247 | unsigned hash = sfq_hash(q, skb); | |
248 | sfq_index x; | |
249 | ||
250 | x = q->ht[hash]; | |
251 | if (x == SFQ_DEPTH) { | |
252 | q->ht[hash] = x = q->dep[SFQ_DEPTH].next; | |
253 | q->hash[x] = hash; | |
254 | } | |
32740ddc AK |
255 | /* If selected queue has length q->limit, this means that |
256 | * all another queues are empty and that we do simple tail drop, | |
257 | * i.e. drop _this_ packet. | |
258 | */ | |
259 | if (q->qs[x].qlen >= q->limit) | |
260 | return qdisc_drop(skb, sch); | |
261 | ||
f5539eb8 | 262 | sch->qstats.backlog += skb->len; |
1da177e4 LT |
263 | __skb_queue_tail(&q->qs[x], skb); |
264 | sfq_inc(q, x); | |
265 | if (q->qs[x].qlen == 1) { /* The flow is new */ | |
266 | if (q->tail == SFQ_DEPTH) { /* It is the first flow */ | |
267 | q->tail = x; | |
268 | q->next[x] = x; | |
269 | q->allot[x] = q->quantum; | |
270 | } else { | |
271 | q->next[x] = q->next[q->tail]; | |
272 | q->next[q->tail] = x; | |
273 | q->tail = x; | |
274 | } | |
275 | } | |
5588b40d | 276 | if (++sch->q.qlen <= q->limit) { |
1da177e4 LT |
277 | sch->bstats.bytes += skb->len; |
278 | sch->bstats.packets++; | |
279 | return 0; | |
280 | } | |
281 | ||
282 | sfq_drop(sch); | |
283 | return NET_XMIT_CN; | |
284 | } | |
285 | ||
286 | static int | |
287 | sfq_requeue(struct sk_buff *skb, struct Qdisc* sch) | |
288 | { | |
289 | struct sfq_sched_data *q = qdisc_priv(sch); | |
290 | unsigned hash = sfq_hash(q, skb); | |
291 | sfq_index x; | |
292 | ||
293 | x = q->ht[hash]; | |
294 | if (x == SFQ_DEPTH) { | |
295 | q->ht[hash] = x = q->dep[SFQ_DEPTH].next; | |
296 | q->hash[x] = hash; | |
297 | } | |
f5539eb8 | 298 | sch->qstats.backlog += skb->len; |
1da177e4 | 299 | __skb_queue_head(&q->qs[x], skb); |
32740ddc AK |
300 | /* If selected queue has length q->limit+1, this means that |
301 | * all another queues are empty and we do simple tail drop. | |
302 | * This packet is still requeued at head of queue, tail packet | |
303 | * is dropped. | |
304 | */ | |
305 | if (q->qs[x].qlen > q->limit) { | |
306 | skb = q->qs[x].prev; | |
307 | __skb_unlink(skb, &q->qs[x]); | |
308 | sch->qstats.drops++; | |
309 | sch->qstats.backlog -= skb->len; | |
310 | kfree_skb(skb); | |
311 | return NET_XMIT_CN; | |
312 | } | |
1da177e4 LT |
313 | sfq_inc(q, x); |
314 | if (q->qs[x].qlen == 1) { /* The flow is new */ | |
315 | if (q->tail == SFQ_DEPTH) { /* It is the first flow */ | |
316 | q->tail = x; | |
317 | q->next[x] = x; | |
318 | q->allot[x] = q->quantum; | |
319 | } else { | |
320 | q->next[x] = q->next[q->tail]; | |
321 | q->next[q->tail] = x; | |
322 | q->tail = x; | |
323 | } | |
324 | } | |
5588b40d | 325 | if (++sch->q.qlen <= q->limit) { |
1da177e4 LT |
326 | sch->qstats.requeues++; |
327 | return 0; | |
328 | } | |
329 | ||
330 | sch->qstats.drops++; | |
331 | sfq_drop(sch); | |
332 | return NET_XMIT_CN; | |
333 | } | |
334 | ||
335 | ||
336 | ||
337 | ||
338 | static struct sk_buff * | |
339 | sfq_dequeue(struct Qdisc* sch) | |
340 | { | |
341 | struct sfq_sched_data *q = qdisc_priv(sch); | |
342 | struct sk_buff *skb; | |
343 | sfq_index a, old_a; | |
344 | ||
345 | /* No active slots */ | |
346 | if (q->tail == SFQ_DEPTH) | |
347 | return NULL; | |
348 | ||
349 | a = old_a = q->next[q->tail]; | |
350 | ||
351 | /* Grab packet */ | |
352 | skb = __skb_dequeue(&q->qs[a]); | |
353 | sfq_dec(q, a); | |
354 | sch->q.qlen--; | |
f5539eb8 | 355 | sch->qstats.backlog -= skb->len; |
1da177e4 LT |
356 | |
357 | /* Is the slot empty? */ | |
358 | if (q->qs[a].qlen == 0) { | |
359 | q->ht[q->hash[a]] = SFQ_DEPTH; | |
360 | a = q->next[a]; | |
361 | if (a == old_a) { | |
362 | q->tail = SFQ_DEPTH; | |
363 | return skb; | |
364 | } | |
365 | q->next[q->tail] = a; | |
366 | q->allot[a] += q->quantum; | |
367 | } else if ((q->allot[a] -= skb->len) <= 0) { | |
368 | q->tail = a; | |
369 | a = q->next[a]; | |
370 | q->allot[a] += q->quantum; | |
371 | } | |
372 | return skb; | |
373 | } | |
374 | ||
375 | static void | |
376 | sfq_reset(struct Qdisc* sch) | |
377 | { | |
378 | struct sk_buff *skb; | |
379 | ||
380 | while ((skb = sfq_dequeue(sch)) != NULL) | |
381 | kfree_skb(skb); | |
382 | } | |
383 | ||
384 | static void sfq_perturbation(unsigned long arg) | |
385 | { | |
386 | struct Qdisc *sch = (struct Qdisc*)arg; | |
387 | struct sfq_sched_data *q = qdisc_priv(sch); | |
388 | ||
32740ddc | 389 | get_random_bytes(&q->perturbation, 4); |
1da177e4 | 390 | |
32740ddc AK |
391 | if (q->perturb_period) |
392 | mod_timer(&q->perturb_timer, jiffies + q->perturb_period); | |
1da177e4 LT |
393 | } |
394 | ||
395 | static int sfq_change(struct Qdisc *sch, struct rtattr *opt) | |
396 | { | |
397 | struct sfq_sched_data *q = qdisc_priv(sch); | |
398 | struct tc_sfq_qopt *ctl = RTA_DATA(opt); | |
5e50da01 | 399 | unsigned int qlen; |
1da177e4 LT |
400 | |
401 | if (opt->rta_len < RTA_LENGTH(sizeof(*ctl))) | |
402 | return -EINVAL; | |
403 | ||
404 | sch_tree_lock(sch); | |
405 | q->quantum = ctl->quantum ? : psched_mtu(sch->dev); | |
406 | q->perturb_period = ctl->perturb_period*HZ; | |
407 | if (ctl->limit) | |
32740ddc | 408 | q->limit = min_t(u32, ctl->limit, SFQ_DEPTH - 1); |
1da177e4 | 409 | |
5e50da01 | 410 | qlen = sch->q.qlen; |
5588b40d | 411 | while (sch->q.qlen > q->limit) |
1da177e4 | 412 | sfq_drop(sch); |
5e50da01 | 413 | qdisc_tree_decrease_qlen(sch, qlen - sch->q.qlen); |
1da177e4 LT |
414 | |
415 | del_timer(&q->perturb_timer); | |
416 | if (q->perturb_period) { | |
32740ddc AK |
417 | mod_timer(&q->perturb_timer, jiffies + q->perturb_period); |
418 | get_random_bytes(&q->perturbation, 4); | |
1da177e4 LT |
419 | } |
420 | sch_tree_unlock(sch); | |
421 | return 0; | |
422 | } | |
423 | ||
424 | static int sfq_init(struct Qdisc *sch, struct rtattr *opt) | |
425 | { | |
426 | struct sfq_sched_data *q = qdisc_priv(sch); | |
427 | int i; | |
428 | ||
b24b8a24 | 429 | setup_timer(&q->perturb_timer, sfq_perturbation, (unsigned long)sch); |
1da177e4 LT |
430 | |
431 | for (i=0; i<SFQ_HASH_DIVISOR; i++) | |
432 | q->ht[i] = SFQ_DEPTH; | |
433 | for (i=0; i<SFQ_DEPTH; i++) { | |
434 | skb_queue_head_init(&q->qs[i]); | |
435 | q->dep[i+SFQ_DEPTH].next = i+SFQ_DEPTH; | |
436 | q->dep[i+SFQ_DEPTH].prev = i+SFQ_DEPTH; | |
437 | } | |
32740ddc | 438 | q->limit = SFQ_DEPTH - 1; |
1da177e4 LT |
439 | q->max_depth = 0; |
440 | q->tail = SFQ_DEPTH; | |
441 | if (opt == NULL) { | |
442 | q->quantum = psched_mtu(sch->dev); | |
443 | q->perturb_period = 0; | |
32740ddc | 444 | get_random_bytes(&q->perturbation, 4); |
1da177e4 LT |
445 | } else { |
446 | int err = sfq_change(sch, opt); | |
447 | if (err) | |
448 | return err; | |
449 | } | |
450 | for (i=0; i<SFQ_DEPTH; i++) | |
451 | sfq_link(q, i); | |
452 | return 0; | |
453 | } | |
454 | ||
455 | static void sfq_destroy(struct Qdisc *sch) | |
456 | { | |
457 | struct sfq_sched_data *q = qdisc_priv(sch); | |
458 | del_timer(&q->perturb_timer); | |
459 | } | |
460 | ||
461 | static int sfq_dump(struct Qdisc *sch, struct sk_buff *skb) | |
462 | { | |
463 | struct sfq_sched_data *q = qdisc_priv(sch); | |
27a884dc | 464 | unsigned char *b = skb_tail_pointer(skb); |
1da177e4 LT |
465 | struct tc_sfq_qopt opt; |
466 | ||
467 | opt.quantum = q->quantum; | |
468 | opt.perturb_period = q->perturb_period/HZ; | |
469 | ||
470 | opt.limit = q->limit; | |
471 | opt.divisor = SFQ_HASH_DIVISOR; | |
472 | opt.flows = q->limit; | |
473 | ||
474 | RTA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt); | |
475 | ||
476 | return skb->len; | |
477 | ||
478 | rtattr_failure: | |
dc5fc579 | 479 | nlmsg_trim(skb, b); |
1da177e4 LT |
480 | return -1; |
481 | } | |
482 | ||
20fea08b | 483 | static struct Qdisc_ops sfq_qdisc_ops __read_mostly = { |
1da177e4 LT |
484 | .next = NULL, |
485 | .cl_ops = NULL, | |
486 | .id = "sfq", | |
487 | .priv_size = sizeof(struct sfq_sched_data), | |
488 | .enqueue = sfq_enqueue, | |
489 | .dequeue = sfq_dequeue, | |
490 | .requeue = sfq_requeue, | |
491 | .drop = sfq_drop, | |
492 | .init = sfq_init, | |
493 | .reset = sfq_reset, | |
494 | .destroy = sfq_destroy, | |
495 | .change = NULL, | |
496 | .dump = sfq_dump, | |
497 | .owner = THIS_MODULE, | |
498 | }; | |
499 | ||
500 | static int __init sfq_module_init(void) | |
501 | { | |
502 | return register_qdisc(&sfq_qdisc_ops); | |
503 | } | |
10297b99 | 504 | static void __exit sfq_module_exit(void) |
1da177e4 LT |
505 | { |
506 | unregister_qdisc(&sfq_qdisc_ops); | |
507 | } | |
508 | module_init(sfq_module_init) | |
509 | module_exit(sfq_module_exit) | |
510 | MODULE_LICENSE("GPL"); |