Commit | Line | Data |
---|---|---|
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 | ||
12 | #include <linux/config.h> | |
13 | #include <linux/module.h> | |
14 | #include <asm/uaccess.h> | |
15 | #include <asm/system.h> | |
16 | #include <linux/bitops.h> | |
17 | #include <linux/types.h> | |
18 | #include <linux/kernel.h> | |
19 | #include <linux/jiffies.h> | |
20 | #include <linux/string.h> | |
21 | #include <linux/mm.h> | |
22 | #include <linux/socket.h> | |
23 | #include <linux/sockios.h> | |
24 | #include <linux/in.h> | |
25 | #include <linux/errno.h> | |
26 | #include <linux/interrupt.h> | |
27 | #include <linux/if_ether.h> | |
28 | #include <linux/inet.h> | |
29 | #include <linux/netdevice.h> | |
30 | #include <linux/etherdevice.h> | |
31 | #include <linux/notifier.h> | |
32 | #include <linux/init.h> | |
33 | #include <net/ip.h> | |
34 | #include <linux/ipv6.h> | |
35 | #include <net/route.h> | |
36 | #include <linux/skbuff.h> | |
37 | #include <net/sock.h> | |
38 | #include <net/pkt_sched.h> | |
39 | ||
40 | ||
41 | /* Stochastic Fairness Queuing algorithm. | |
42 | ======================================= | |
43 | ||
44 | Source: | |
45 | Paul E. McKenney "Stochastic Fairness Queuing", | |
46 | IEEE INFOCOMM'90 Proceedings, San Francisco, 1990. | |
47 | ||
48 | Paul E. McKenney "Stochastic Fairness Queuing", | |
49 | "Interworking: Research and Experience", v.2, 1991, p.113-131. | |
50 | ||
51 | ||
52 | See also: | |
53 | M. Shreedhar and George Varghese "Efficient Fair | |
54 | Queuing using Deficit Round Robin", Proc. SIGCOMM 95. | |
55 | ||
56 | ||
57 | This is not the thing that is usually called (W)FQ nowadays. | |
58 | It does not use any timestamp mechanism, but instead | |
59 | processes queues in round-robin order. | |
60 | ||
61 | ADVANTAGE: | |
62 | ||
63 | - It is very cheap. Both CPU and memory requirements are minimal. | |
64 | ||
65 | DRAWBACKS: | |
66 | ||
67 | - "Stochastic" -> It is not 100% fair. | |
68 | When hash collisions occur, several flows are considered as one. | |
69 | ||
70 | - "Round-robin" -> It introduces larger delays than virtual clock | |
71 | based schemes, and should not be used for isolating interactive | |
72 | traffic from non-interactive. It means, that this scheduler | |
73 | should be used as leaf of CBQ or P3, which put interactive traffic | |
74 | to higher priority band. | |
75 | ||
76 | We still need true WFQ for top level CSZ, but using WFQ | |
77 | for the best effort traffic is absolutely pointless: | |
78 | SFQ is superior for this purpose. | |
79 | ||
80 | IMPLEMENTATION: | |
81 | This implementation limits maximal queue length to 128; | |
82 | maximal mtu to 2^15-1; number of hash buckets to 1024. | |
83 | The only goal of this restrictions was that all data | |
84 | fit into one 4K page :-). Struct sfq_sched_data is | |
85 | organized in anti-cache manner: all the data for a bucket | |
86 | are scattered over different locations. This is not good, | |
87 | but it allowed me to put it into 4K. | |
88 | ||
89 | It is easy to increase these values, but not in flight. */ | |
90 | ||
91 | #define SFQ_DEPTH 128 | |
92 | #define SFQ_HASH_DIVISOR 1024 | |
93 | ||
94 | /* This type should contain at least SFQ_DEPTH*2 values */ | |
95 | typedef unsigned char sfq_index; | |
96 | ||
97 | struct sfq_head | |
98 | { | |
99 | sfq_index next; | |
100 | sfq_index prev; | |
101 | }; | |
102 | ||
103 | struct sfq_sched_data | |
104 | { | |
105 | /* Parameters */ | |
106 | int perturb_period; | |
107 | unsigned quantum; /* Allotment per round: MUST BE >= MTU */ | |
108 | int limit; | |
109 | ||
110 | /* Variables */ | |
111 | struct timer_list perturb_timer; | |
112 | int perturbation; | |
113 | sfq_index tail; /* Index of current slot in round */ | |
114 | sfq_index max_depth; /* Maximal depth */ | |
115 | ||
116 | sfq_index ht[SFQ_HASH_DIVISOR]; /* Hash table */ | |
117 | sfq_index next[SFQ_DEPTH]; /* Active slots link */ | |
118 | short allot[SFQ_DEPTH]; /* Current allotment per slot */ | |
119 | unsigned short hash[SFQ_DEPTH]; /* Hash value indexed by slots */ | |
120 | struct sk_buff_head qs[SFQ_DEPTH]; /* Slot queue */ | |
121 | struct sfq_head dep[SFQ_DEPTH*2]; /* Linked list of slots, indexed by depth */ | |
122 | }; | |
123 | ||
124 | static __inline__ unsigned sfq_fold_hash(struct sfq_sched_data *q, u32 h, u32 h1) | |
125 | { | |
126 | int pert = q->perturbation; | |
127 | ||
128 | /* Have we any rotation primitives? If not, WHY? */ | |
129 | h ^= (h1<<pert) ^ (h1>>(0x1F - pert)); | |
130 | h ^= h>>10; | |
131 | return h & 0x3FF; | |
132 | } | |
133 | ||
134 | static unsigned sfq_hash(struct sfq_sched_data *q, struct sk_buff *skb) | |
135 | { | |
136 | u32 h, h2; | |
137 | ||
138 | switch (skb->protocol) { | |
139 | case __constant_htons(ETH_P_IP): | |
140 | { | |
141 | struct iphdr *iph = skb->nh.iph; | |
142 | h = iph->daddr; | |
143 | h2 = iph->saddr^iph->protocol; | |
144 | if (!(iph->frag_off&htons(IP_MF|IP_OFFSET)) && | |
145 | (iph->protocol == IPPROTO_TCP || | |
146 | iph->protocol == IPPROTO_UDP || | |
147 | iph->protocol == IPPROTO_ESP)) | |
148 | h2 ^= *(((u32*)iph) + iph->ihl); | |
149 | break; | |
150 | } | |
151 | case __constant_htons(ETH_P_IPV6): | |
152 | { | |
153 | struct ipv6hdr *iph = skb->nh.ipv6h; | |
154 | h = iph->daddr.s6_addr32[3]; | |
155 | h2 = iph->saddr.s6_addr32[3]^iph->nexthdr; | |
156 | if (iph->nexthdr == IPPROTO_TCP || | |
157 | iph->nexthdr == IPPROTO_UDP || | |
158 | iph->nexthdr == IPPROTO_ESP) | |
159 | h2 ^= *(u32*)&iph[1]; | |
160 | break; | |
161 | } | |
162 | default: | |
163 | h = (u32)(unsigned long)skb->dst^skb->protocol; | |
164 | h2 = (u32)(unsigned long)skb->sk; | |
165 | } | |
166 | return sfq_fold_hash(q, h, h2); | |
167 | } | |
168 | ||
169 | static inline void sfq_link(struct sfq_sched_data *q, sfq_index x) | |
170 | { | |
171 | sfq_index p, n; | |
172 | int d = q->qs[x].qlen + SFQ_DEPTH; | |
173 | ||
174 | p = d; | |
175 | n = q->dep[d].next; | |
176 | q->dep[x].next = n; | |
177 | q->dep[x].prev = p; | |
178 | q->dep[p].next = q->dep[n].prev = x; | |
179 | } | |
180 | ||
181 | static inline void sfq_dec(struct sfq_sched_data *q, sfq_index x) | |
182 | { | |
183 | sfq_index p, n; | |
184 | ||
185 | n = q->dep[x].next; | |
186 | p = q->dep[x].prev; | |
187 | q->dep[p].next = n; | |
188 | q->dep[n].prev = p; | |
189 | ||
190 | if (n == p && q->max_depth == q->qs[x].qlen + 1) | |
191 | q->max_depth--; | |
192 | ||
193 | sfq_link(q, x); | |
194 | } | |
195 | ||
196 | static inline void sfq_inc(struct sfq_sched_data *q, sfq_index x) | |
197 | { | |
198 | sfq_index p, n; | |
199 | int d; | |
200 | ||
201 | n = q->dep[x].next; | |
202 | p = q->dep[x].prev; | |
203 | q->dep[p].next = n; | |
204 | q->dep[n].prev = p; | |
205 | d = q->qs[x].qlen; | |
206 | if (q->max_depth < d) | |
207 | q->max_depth = d; | |
208 | ||
209 | sfq_link(q, x); | |
210 | } | |
211 | ||
212 | static unsigned int sfq_drop(struct Qdisc *sch) | |
213 | { | |
214 | struct sfq_sched_data *q = qdisc_priv(sch); | |
215 | sfq_index d = q->max_depth; | |
216 | struct sk_buff *skb; | |
217 | unsigned int len; | |
218 | ||
219 | /* Queue is full! Find the longest slot and | |
220 | drop a packet from it */ | |
221 | ||
222 | if (d > 1) { | |
223 | sfq_index x = q->dep[d+SFQ_DEPTH].next; | |
224 | skb = q->qs[x].prev; | |
225 | len = skb->len; | |
226 | __skb_unlink(skb, &q->qs[x]); | |
227 | kfree_skb(skb); | |
228 | sfq_dec(q, x); | |
229 | sch->q.qlen--; | |
230 | sch->qstats.drops++; | |
231 | return len; | |
232 | } | |
233 | ||
234 | if (d == 1) { | |
235 | /* It is difficult to believe, but ALL THE SLOTS HAVE LENGTH 1. */ | |
236 | d = q->next[q->tail]; | |
237 | q->next[q->tail] = q->next[d]; | |
238 | q->allot[q->next[d]] += q->quantum; | |
239 | skb = q->qs[d].prev; | |
240 | len = skb->len; | |
241 | __skb_unlink(skb, &q->qs[d]); | |
242 | kfree_skb(skb); | |
243 | sfq_dec(q, d); | |
244 | sch->q.qlen--; | |
245 | q->ht[q->hash[d]] = SFQ_DEPTH; | |
246 | sch->qstats.drops++; | |
247 | return len; | |
248 | } | |
249 | ||
250 | return 0; | |
251 | } | |
252 | ||
253 | static int | |
254 | sfq_enqueue(struct sk_buff *skb, struct Qdisc* sch) | |
255 | { | |
256 | struct sfq_sched_data *q = qdisc_priv(sch); | |
257 | unsigned hash = sfq_hash(q, skb); | |
258 | sfq_index x; | |
259 | ||
260 | x = q->ht[hash]; | |
261 | if (x == SFQ_DEPTH) { | |
262 | q->ht[hash] = x = q->dep[SFQ_DEPTH].next; | |
263 | q->hash[x] = hash; | |
264 | } | |
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 | } | |
278 | if (++sch->q.qlen < q->limit-1) { | |
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 | |
289 | sfq_requeue(struct sk_buff *skb, struct Qdisc* sch) | |
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 | } | |
300 | __skb_queue_head(&q->qs[x], skb); | |
301 | sfq_inc(q, x); | |
302 | if (q->qs[x].qlen == 1) { /* The flow is new */ | |
303 | if (q->tail == SFQ_DEPTH) { /* It is the first flow */ | |
304 | q->tail = x; | |
305 | q->next[x] = x; | |
306 | q->allot[x] = q->quantum; | |
307 | } else { | |
308 | q->next[x] = q->next[q->tail]; | |
309 | q->next[q->tail] = x; | |
310 | q->tail = x; | |
311 | } | |
312 | } | |
313 | if (++sch->q.qlen < q->limit - 1) { | |
314 | sch->qstats.requeues++; | |
315 | return 0; | |
316 | } | |
317 | ||
318 | sch->qstats.drops++; | |
319 | sfq_drop(sch); | |
320 | return NET_XMIT_CN; | |
321 | } | |
322 | ||
323 | ||
324 | ||
325 | ||
326 | static struct sk_buff * | |
327 | sfq_dequeue(struct Qdisc* sch) | |
328 | { | |
329 | struct sfq_sched_data *q = qdisc_priv(sch); | |
330 | struct sk_buff *skb; | |
331 | sfq_index a, old_a; | |
332 | ||
333 | /* No active slots */ | |
334 | if (q->tail == SFQ_DEPTH) | |
335 | return NULL; | |
336 | ||
337 | a = old_a = q->next[q->tail]; | |
338 | ||
339 | /* Grab packet */ | |
340 | skb = __skb_dequeue(&q->qs[a]); | |
341 | sfq_dec(q, a); | |
342 | sch->q.qlen--; | |
343 | ||
344 | /* Is the slot empty? */ | |
345 | if (q->qs[a].qlen == 0) { | |
346 | q->ht[q->hash[a]] = SFQ_DEPTH; | |
347 | a = q->next[a]; | |
348 | if (a == old_a) { | |
349 | q->tail = SFQ_DEPTH; | |
350 | return skb; | |
351 | } | |
352 | q->next[q->tail] = a; | |
353 | q->allot[a] += q->quantum; | |
354 | } else if ((q->allot[a] -= skb->len) <= 0) { | |
355 | q->tail = a; | |
356 | a = q->next[a]; | |
357 | q->allot[a] += q->quantum; | |
358 | } | |
359 | return skb; | |
360 | } | |
361 | ||
362 | static void | |
363 | sfq_reset(struct Qdisc* sch) | |
364 | { | |
365 | struct sk_buff *skb; | |
366 | ||
367 | while ((skb = sfq_dequeue(sch)) != NULL) | |
368 | kfree_skb(skb); | |
369 | } | |
370 | ||
371 | static void sfq_perturbation(unsigned long arg) | |
372 | { | |
373 | struct Qdisc *sch = (struct Qdisc*)arg; | |
374 | struct sfq_sched_data *q = qdisc_priv(sch); | |
375 | ||
376 | q->perturbation = net_random()&0x1F; | |
377 | ||
378 | if (q->perturb_period) { | |
379 | q->perturb_timer.expires = jiffies + q->perturb_period; | |
380 | add_timer(&q->perturb_timer); | |
381 | } | |
382 | } | |
383 | ||
384 | static int sfq_change(struct Qdisc *sch, struct rtattr *opt) | |
385 | { | |
386 | struct sfq_sched_data *q = qdisc_priv(sch); | |
387 | struct tc_sfq_qopt *ctl = RTA_DATA(opt); | |
388 | ||
389 | if (opt->rta_len < RTA_LENGTH(sizeof(*ctl))) | |
390 | return -EINVAL; | |
391 | ||
392 | sch_tree_lock(sch); | |
393 | q->quantum = ctl->quantum ? : psched_mtu(sch->dev); | |
394 | q->perturb_period = ctl->perturb_period*HZ; | |
395 | if (ctl->limit) | |
396 | q->limit = min_t(u32, ctl->limit, SFQ_DEPTH); | |
397 | ||
398 | while (sch->q.qlen >= q->limit-1) | |
399 | sfq_drop(sch); | |
400 | ||
401 | del_timer(&q->perturb_timer); | |
402 | if (q->perturb_period) { | |
403 | q->perturb_timer.expires = jiffies + q->perturb_period; | |
404 | add_timer(&q->perturb_timer); | |
405 | } | |
406 | sch_tree_unlock(sch); | |
407 | return 0; | |
408 | } | |
409 | ||
410 | static int sfq_init(struct Qdisc *sch, struct rtattr *opt) | |
411 | { | |
412 | struct sfq_sched_data *q = qdisc_priv(sch); | |
413 | int i; | |
414 | ||
415 | init_timer(&q->perturb_timer); | |
416 | q->perturb_timer.data = (unsigned long)sch; | |
417 | q->perturb_timer.function = sfq_perturbation; | |
418 | ||
419 | for (i=0; i<SFQ_HASH_DIVISOR; i++) | |
420 | q->ht[i] = SFQ_DEPTH; | |
421 | for (i=0; i<SFQ_DEPTH; i++) { | |
422 | skb_queue_head_init(&q->qs[i]); | |
423 | q->dep[i+SFQ_DEPTH].next = i+SFQ_DEPTH; | |
424 | q->dep[i+SFQ_DEPTH].prev = i+SFQ_DEPTH; | |
425 | } | |
426 | q->limit = SFQ_DEPTH; | |
427 | q->max_depth = 0; | |
428 | q->tail = SFQ_DEPTH; | |
429 | if (opt == NULL) { | |
430 | q->quantum = psched_mtu(sch->dev); | |
431 | q->perturb_period = 0; | |
432 | } else { | |
433 | int err = sfq_change(sch, opt); | |
434 | if (err) | |
435 | return err; | |
436 | } | |
437 | for (i=0; i<SFQ_DEPTH; i++) | |
438 | sfq_link(q, i); | |
439 | return 0; | |
440 | } | |
441 | ||
442 | static void sfq_destroy(struct Qdisc *sch) | |
443 | { | |
444 | struct sfq_sched_data *q = qdisc_priv(sch); | |
445 | del_timer(&q->perturb_timer); | |
446 | } | |
447 | ||
448 | static int sfq_dump(struct Qdisc *sch, struct sk_buff *skb) | |
449 | { | |
450 | struct sfq_sched_data *q = qdisc_priv(sch); | |
451 | unsigned char *b = skb->tail; | |
452 | struct tc_sfq_qopt opt; | |
453 | ||
454 | opt.quantum = q->quantum; | |
455 | opt.perturb_period = q->perturb_period/HZ; | |
456 | ||
457 | opt.limit = q->limit; | |
458 | opt.divisor = SFQ_HASH_DIVISOR; | |
459 | opt.flows = q->limit; | |
460 | ||
461 | RTA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt); | |
462 | ||
463 | return skb->len; | |
464 | ||
465 | rtattr_failure: | |
466 | skb_trim(skb, b - skb->data); | |
467 | return -1; | |
468 | } | |
469 | ||
470 | static struct Qdisc_ops sfq_qdisc_ops = { | |
471 | .next = NULL, | |
472 | .cl_ops = NULL, | |
473 | .id = "sfq", | |
474 | .priv_size = sizeof(struct sfq_sched_data), | |
475 | .enqueue = sfq_enqueue, | |
476 | .dequeue = sfq_dequeue, | |
477 | .requeue = sfq_requeue, | |
478 | .drop = sfq_drop, | |
479 | .init = sfq_init, | |
480 | .reset = sfq_reset, | |
481 | .destroy = sfq_destroy, | |
482 | .change = NULL, | |
483 | .dump = sfq_dump, | |
484 | .owner = THIS_MODULE, | |
485 | }; | |
486 | ||
487 | static int __init sfq_module_init(void) | |
488 | { | |
489 | return register_qdisc(&sfq_qdisc_ops); | |
490 | } | |
491 | static void __exit sfq_module_exit(void) | |
492 | { | |
493 | unregister_qdisc(&sfq_qdisc_ops); | |
494 | } | |
495 | module_init(sfq_module_init) | |
496 | module_exit(sfq_module_exit) | |
497 | MODULE_LICENSE("GPL"); |