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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 | 124 | h = iph->daddr; |
6f9e98f7 | 125 | h2 = iph->saddr ^ iph->protocol; |
1da177e4 LT |
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 | 139 | h = iph->daddr.s6_addr32[3]; |
6f9e98f7 | 140 | h2 = iph->saddr.s6_addr32[3] ^ iph->nexthdr; |
1da177e4 LT |
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: | |
6f9e98f7 SH |
151 | h = (unsigned long)skb->dst ^ skb->protocol; |
152 | h2 = (unsigned long)skb->sk; | |
1da177e4 | 153 | } |
6f9e98f7 | 154 | |
1da177e4 LT |
155 | return sfq_fold_hash(q, h, h2); |
156 | } | |
157 | ||
158 | static inline void sfq_link(struct sfq_sched_data *q, sfq_index x) | |
159 | { | |
160 | sfq_index p, n; | |
161 | int d = q->qs[x].qlen + SFQ_DEPTH; | |
162 | ||
163 | p = d; | |
164 | n = q->dep[d].next; | |
165 | q->dep[x].next = n; | |
166 | q->dep[x].prev = p; | |
167 | q->dep[p].next = q->dep[n].prev = x; | |
168 | } | |
169 | ||
170 | static inline void sfq_dec(struct sfq_sched_data *q, sfq_index x) | |
171 | { | |
172 | sfq_index p, n; | |
173 | ||
174 | n = q->dep[x].next; | |
175 | p = q->dep[x].prev; | |
176 | q->dep[p].next = n; | |
177 | q->dep[n].prev = p; | |
178 | ||
179 | if (n == p && q->max_depth == q->qs[x].qlen + 1) | |
180 | q->max_depth--; | |
181 | ||
182 | sfq_link(q, x); | |
183 | } | |
184 | ||
185 | static inline void sfq_inc(struct sfq_sched_data *q, sfq_index x) | |
186 | { | |
187 | sfq_index p, n; | |
188 | int d; | |
189 | ||
190 | n = q->dep[x].next; | |
191 | p = q->dep[x].prev; | |
192 | q->dep[p].next = n; | |
193 | q->dep[n].prev = p; | |
194 | d = q->qs[x].qlen; | |
195 | if (q->max_depth < d) | |
196 | q->max_depth = d; | |
197 | ||
198 | sfq_link(q, x); | |
199 | } | |
200 | ||
201 | static unsigned int sfq_drop(struct Qdisc *sch) | |
202 | { | |
203 | struct sfq_sched_data *q = qdisc_priv(sch); | |
204 | sfq_index d = q->max_depth; | |
205 | struct sk_buff *skb; | |
206 | unsigned int len; | |
207 | ||
208 | /* Queue is full! Find the longest slot and | |
209 | drop a packet from it */ | |
210 | ||
211 | if (d > 1) { | |
6f9e98f7 | 212 | sfq_index x = q->dep[d + SFQ_DEPTH].next; |
1da177e4 LT |
213 | skb = q->qs[x].prev; |
214 | len = skb->len; | |
215 | __skb_unlink(skb, &q->qs[x]); | |
216 | kfree_skb(skb); | |
217 | sfq_dec(q, x); | |
218 | sch->q.qlen--; | |
219 | sch->qstats.drops++; | |
f5539eb8 | 220 | sch->qstats.backlog -= len; |
1da177e4 LT |
221 | return len; |
222 | } | |
223 | ||
224 | if (d == 1) { | |
225 | /* It is difficult to believe, but ALL THE SLOTS HAVE LENGTH 1. */ | |
226 | d = q->next[q->tail]; | |
227 | q->next[q->tail] = q->next[d]; | |
228 | q->allot[q->next[d]] += q->quantum; | |
229 | skb = q->qs[d].prev; | |
230 | len = skb->len; | |
231 | __skb_unlink(skb, &q->qs[d]); | |
232 | kfree_skb(skb); | |
233 | sfq_dec(q, d); | |
234 | sch->q.qlen--; | |
235 | q->ht[q->hash[d]] = SFQ_DEPTH; | |
236 | sch->qstats.drops++; | |
f5539eb8 | 237 | sch->qstats.backlog -= len; |
1da177e4 LT |
238 | return len; |
239 | } | |
240 | ||
241 | return 0; | |
242 | } | |
243 | ||
244 | static int | |
6f9e98f7 | 245 | sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch) |
1da177e4 LT |
246 | { |
247 | struct sfq_sched_data *q = qdisc_priv(sch); | |
248 | unsigned hash = sfq_hash(q, skb); | |
249 | sfq_index x; | |
250 | ||
251 | x = q->ht[hash]; | |
252 | if (x == SFQ_DEPTH) { | |
253 | q->ht[hash] = x = q->dep[SFQ_DEPTH].next; | |
254 | q->hash[x] = hash; | |
255 | } | |
6f9e98f7 | 256 | |
32740ddc AK |
257 | /* If selected queue has length q->limit, this means that |
258 | * all another queues are empty and that we do simple tail drop, | |
259 | * i.e. drop _this_ packet. | |
260 | */ | |
261 | if (q->qs[x].qlen >= q->limit) | |
262 | return qdisc_drop(skb, sch); | |
263 | ||
f5539eb8 | 264 | sch->qstats.backlog += skb->len; |
1da177e4 LT |
265 | __skb_queue_tail(&q->qs[x], skb); |
266 | sfq_inc(q, x); | |
267 | if (q->qs[x].qlen == 1) { /* The flow is new */ | |
268 | if (q->tail == SFQ_DEPTH) { /* It is the first flow */ | |
269 | q->tail = x; | |
270 | q->next[x] = x; | |
271 | q->allot[x] = q->quantum; | |
272 | } else { | |
273 | q->next[x] = q->next[q->tail]; | |
274 | q->next[q->tail] = x; | |
275 | q->tail = x; | |
276 | } | |
277 | } | |
5588b40d | 278 | if (++sch->q.qlen <= q->limit) { |
1da177e4 LT |
279 | sch->bstats.bytes += skb->len; |
280 | sch->bstats.packets++; | |
281 | return 0; | |
282 | } | |
283 | ||
284 | sfq_drop(sch); | |
285 | return NET_XMIT_CN; | |
286 | } | |
287 | ||
288 | static int | |
6f9e98f7 | 289 | sfq_requeue(struct sk_buff *skb, struct Qdisc *sch) |
1da177e4 LT |
290 | { |
291 | struct sfq_sched_data *q = qdisc_priv(sch); | |
292 | unsigned hash = sfq_hash(q, skb); | |
293 | sfq_index x; | |
294 | ||
295 | x = q->ht[hash]; | |
296 | if (x == SFQ_DEPTH) { | |
297 | q->ht[hash] = x = q->dep[SFQ_DEPTH].next; | |
298 | q->hash[x] = hash; | |
299 | } | |
6f9e98f7 | 300 | |
f5539eb8 | 301 | sch->qstats.backlog += skb->len; |
1da177e4 | 302 | __skb_queue_head(&q->qs[x], skb); |
32740ddc AK |
303 | /* If selected queue has length q->limit+1, this means that |
304 | * all another queues are empty and we do simple tail drop. | |
305 | * This packet is still requeued at head of queue, tail packet | |
306 | * is dropped. | |
307 | */ | |
308 | if (q->qs[x].qlen > q->limit) { | |
309 | skb = q->qs[x].prev; | |
310 | __skb_unlink(skb, &q->qs[x]); | |
311 | sch->qstats.drops++; | |
312 | sch->qstats.backlog -= skb->len; | |
313 | kfree_skb(skb); | |
314 | return NET_XMIT_CN; | |
315 | } | |
6f9e98f7 | 316 | |
1da177e4 LT |
317 | sfq_inc(q, x); |
318 | if (q->qs[x].qlen == 1) { /* The flow is new */ | |
319 | if (q->tail == SFQ_DEPTH) { /* It is the first flow */ | |
320 | q->tail = x; | |
321 | q->next[x] = x; | |
322 | q->allot[x] = q->quantum; | |
323 | } else { | |
324 | q->next[x] = q->next[q->tail]; | |
325 | q->next[q->tail] = x; | |
326 | q->tail = x; | |
327 | } | |
328 | } | |
6f9e98f7 | 329 | |
5588b40d | 330 | if (++sch->q.qlen <= q->limit) { |
1da177e4 LT |
331 | sch->qstats.requeues++; |
332 | return 0; | |
333 | } | |
334 | ||
335 | sch->qstats.drops++; | |
336 | sfq_drop(sch); | |
337 | return NET_XMIT_CN; | |
338 | } | |
339 | ||
340 | ||
341 | ||
342 | ||
343 | static struct sk_buff * | |
6f9e98f7 | 344 | sfq_dequeue(struct Qdisc *sch) |
1da177e4 LT |
345 | { |
346 | struct sfq_sched_data *q = qdisc_priv(sch); | |
347 | struct sk_buff *skb; | |
348 | sfq_index a, old_a; | |
349 | ||
350 | /* No active slots */ | |
351 | if (q->tail == SFQ_DEPTH) | |
352 | return NULL; | |
353 | ||
354 | a = old_a = q->next[q->tail]; | |
355 | ||
356 | /* Grab packet */ | |
357 | skb = __skb_dequeue(&q->qs[a]); | |
358 | sfq_dec(q, a); | |
359 | sch->q.qlen--; | |
f5539eb8 | 360 | sch->qstats.backlog -= skb->len; |
1da177e4 LT |
361 | |
362 | /* Is the slot empty? */ | |
363 | if (q->qs[a].qlen == 0) { | |
364 | q->ht[q->hash[a]] = SFQ_DEPTH; | |
365 | a = q->next[a]; | |
366 | if (a == old_a) { | |
367 | q->tail = SFQ_DEPTH; | |
368 | return skb; | |
369 | } | |
370 | q->next[q->tail] = a; | |
371 | q->allot[a] += q->quantum; | |
372 | } else if ((q->allot[a] -= skb->len) <= 0) { | |
373 | q->tail = a; | |
374 | a = q->next[a]; | |
375 | q->allot[a] += q->quantum; | |
376 | } | |
377 | return skb; | |
378 | } | |
379 | ||
380 | static void | |
6f9e98f7 | 381 | sfq_reset(struct Qdisc *sch) |
1da177e4 LT |
382 | { |
383 | struct sk_buff *skb; | |
384 | ||
385 | while ((skb = sfq_dequeue(sch)) != NULL) | |
386 | kfree_skb(skb); | |
387 | } | |
388 | ||
389 | static void sfq_perturbation(unsigned long arg) | |
390 | { | |
6f9e98f7 | 391 | struct Qdisc *sch = (struct Qdisc *)arg; |
1da177e4 LT |
392 | struct sfq_sched_data *q = qdisc_priv(sch); |
393 | ||
d46f8dd8 | 394 | q->perturbation = net_random(); |
1da177e4 | 395 | |
32740ddc AK |
396 | if (q->perturb_period) |
397 | mod_timer(&q->perturb_timer, jiffies + q->perturb_period); | |
1da177e4 LT |
398 | } |
399 | ||
1e90474c | 400 | static int sfq_change(struct Qdisc *sch, struct nlattr *opt) |
1da177e4 LT |
401 | { |
402 | struct sfq_sched_data *q = qdisc_priv(sch); | |
1e90474c | 403 | struct tc_sfq_qopt *ctl = nla_data(opt); |
5e50da01 | 404 | unsigned int qlen; |
1da177e4 | 405 | |
1e90474c | 406 | if (opt->nla_len < nla_attr_size(sizeof(*ctl))) |
1da177e4 LT |
407 | return -EINVAL; |
408 | ||
409 | sch_tree_lock(sch); | |
410 | q->quantum = ctl->quantum ? : psched_mtu(sch->dev); | |
6f9e98f7 | 411 | q->perturb_period = ctl->perturb_period * HZ; |
1da177e4 | 412 | if (ctl->limit) |
32740ddc | 413 | q->limit = min_t(u32, ctl->limit, SFQ_DEPTH - 1); |
1da177e4 | 414 | |
5e50da01 | 415 | qlen = sch->q.qlen; |
5588b40d | 416 | while (sch->q.qlen > q->limit) |
1da177e4 | 417 | sfq_drop(sch); |
5e50da01 | 418 | qdisc_tree_decrease_qlen(sch, qlen - sch->q.qlen); |
1da177e4 LT |
419 | |
420 | del_timer(&q->perturb_timer); | |
421 | if (q->perturb_period) { | |
32740ddc | 422 | mod_timer(&q->perturb_timer, jiffies + q->perturb_period); |
d46f8dd8 | 423 | q->perturbation = net_random(); |
1da177e4 LT |
424 | } |
425 | sch_tree_unlock(sch); | |
426 | return 0; | |
427 | } | |
428 | ||
1e90474c | 429 | static int sfq_init(struct Qdisc *sch, struct nlattr *opt) |
1da177e4 LT |
430 | { |
431 | struct sfq_sched_data *q = qdisc_priv(sch); | |
432 | int i; | |
433 | ||
d3e99483 SH |
434 | q->perturb_timer.function = sfq_perturbation; |
435 | q->perturb_timer.data = (unsigned long)sch;; | |
436 | init_timer_deferrable(&q->perturb_timer); | |
1da177e4 | 437 | |
6f9e98f7 | 438 | for (i = 0; i < SFQ_HASH_DIVISOR; i++) |
1da177e4 | 439 | q->ht[i] = SFQ_DEPTH; |
6f9e98f7 SH |
440 | |
441 | for (i = 0; i < SFQ_DEPTH; i++) { | |
1da177e4 | 442 | skb_queue_head_init(&q->qs[i]); |
6f9e98f7 SH |
443 | q->dep[i + SFQ_DEPTH].next = i + SFQ_DEPTH; |
444 | q->dep[i + SFQ_DEPTH].prev = i + SFQ_DEPTH; | |
1da177e4 | 445 | } |
6f9e98f7 | 446 | |
32740ddc | 447 | q->limit = SFQ_DEPTH - 1; |
1da177e4 LT |
448 | q->max_depth = 0; |
449 | q->tail = SFQ_DEPTH; | |
450 | if (opt == NULL) { | |
451 | q->quantum = psched_mtu(sch->dev); | |
452 | q->perturb_period = 0; | |
d46f8dd8 | 453 | q->perturbation = net_random(); |
1da177e4 LT |
454 | } else { |
455 | int err = sfq_change(sch, opt); | |
456 | if (err) | |
457 | return err; | |
458 | } | |
6f9e98f7 SH |
459 | |
460 | for (i = 0; i < SFQ_DEPTH; i++) | |
1da177e4 LT |
461 | sfq_link(q, i); |
462 | return 0; | |
463 | } | |
464 | ||
465 | static void sfq_destroy(struct Qdisc *sch) | |
466 | { | |
467 | struct sfq_sched_data *q = qdisc_priv(sch); | |
468 | del_timer(&q->perturb_timer); | |
469 | } | |
470 | ||
471 | static int sfq_dump(struct Qdisc *sch, struct sk_buff *skb) | |
472 | { | |
473 | struct sfq_sched_data *q = qdisc_priv(sch); | |
27a884dc | 474 | unsigned char *b = skb_tail_pointer(skb); |
1da177e4 LT |
475 | struct tc_sfq_qopt opt; |
476 | ||
477 | opt.quantum = q->quantum; | |
6f9e98f7 | 478 | opt.perturb_period = q->perturb_period / HZ; |
1da177e4 LT |
479 | |
480 | opt.limit = q->limit; | |
481 | opt.divisor = SFQ_HASH_DIVISOR; | |
482 | opt.flows = q->limit; | |
483 | ||
1e90474c | 484 | NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt); |
1da177e4 LT |
485 | |
486 | return skb->len; | |
487 | ||
1e90474c | 488 | nla_put_failure: |
dc5fc579 | 489 | nlmsg_trim(skb, b); |
1da177e4 LT |
490 | return -1; |
491 | } | |
492 | ||
20fea08b | 493 | static struct Qdisc_ops sfq_qdisc_ops __read_mostly = { |
1da177e4 LT |
494 | .next = NULL, |
495 | .cl_ops = NULL, | |
496 | .id = "sfq", | |
497 | .priv_size = sizeof(struct sfq_sched_data), | |
498 | .enqueue = sfq_enqueue, | |
499 | .dequeue = sfq_dequeue, | |
500 | .requeue = sfq_requeue, | |
501 | .drop = sfq_drop, | |
502 | .init = sfq_init, | |
503 | .reset = sfq_reset, | |
504 | .destroy = sfq_destroy, | |
505 | .change = NULL, | |
506 | .dump = sfq_dump, | |
507 | .owner = THIS_MODULE, | |
508 | }; | |
509 | ||
510 | static int __init sfq_module_init(void) | |
511 | { | |
512 | return register_qdisc(&sfq_qdisc_ops); | |
513 | } | |
10297b99 | 514 | static void __exit sfq_module_exit(void) |
1da177e4 LT |
515 | { |
516 | unregister_qdisc(&sfq_qdisc_ops); | |
517 | } | |
518 | module_init(sfq_module_init) | |
519 | module_exit(sfq_module_exit) | |
520 | MODULE_LICENSE("GPL"); |