Commit | Line | Data |
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d2912cb1 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
13d2a1d2 PM |
2 | /* |
3 | * net/sched/sch_drr.c Deficit Round Robin scheduler | |
4 | * | |
5 | * Copyright (c) 2008 Patrick McHardy <kaber@trash.net> | |
13d2a1d2 PM |
6 | */ |
7 | ||
8 | #include <linux/module.h> | |
5a0e3ad6 | 9 | #include <linux/slab.h> |
13d2a1d2 PM |
10 | #include <linux/init.h> |
11 | #include <linux/errno.h> | |
12 | #include <linux/netdevice.h> | |
13 | #include <linux/pkt_sched.h> | |
14 | #include <net/sch_generic.h> | |
15 | #include <net/pkt_sched.h> | |
16 | #include <net/pkt_cls.h> | |
17 | ||
18 | struct drr_class { | |
19 | struct Qdisc_class_common common; | |
13d2a1d2 | 20 | |
50dc9a85 | 21 | struct gnet_stats_basic_sync bstats; |
13d2a1d2 | 22 | struct gnet_stats_queue qstats; |
1c0d32fd | 23 | struct net_rate_estimator __rcu *rate_est; |
13d2a1d2 PM |
24 | struct list_head alist; |
25 | struct Qdisc *qdisc; | |
26 | ||
27 | u32 quantum; | |
28 | u32 deficit; | |
29 | }; | |
30 | ||
31 | struct drr_sched { | |
32 | struct list_head active; | |
25d8c0d5 | 33 | struct tcf_proto __rcu *filter_list; |
6529eaba | 34 | struct tcf_block *block; |
13d2a1d2 PM |
35 | struct Qdisc_class_hash clhash; |
36 | }; | |
37 | ||
f99a3fbf VN |
38 | static bool cl_is_active(struct drr_class *cl) |
39 | { | |
40 | return !list_empty(&cl->alist); | |
41 | } | |
42 | ||
13d2a1d2 PM |
43 | static struct drr_class *drr_find_class(struct Qdisc *sch, u32 classid) |
44 | { | |
45 | struct drr_sched *q = qdisc_priv(sch); | |
46 | struct Qdisc_class_common *clc; | |
47 | ||
48 | clc = qdisc_class_find(&q->clhash, classid); | |
49 | if (clc == NULL) | |
50 | return NULL; | |
51 | return container_of(clc, struct drr_class, common); | |
52 | } | |
53 | ||
13d2a1d2 PM |
54 | static const struct nla_policy drr_policy[TCA_DRR_MAX + 1] = { |
55 | [TCA_DRR_QUANTUM] = { .type = NLA_U32 }, | |
56 | }; | |
57 | ||
58 | static int drr_change_class(struct Qdisc *sch, u32 classid, u32 parentid, | |
793d81d6 AA |
59 | struct nlattr **tca, unsigned long *arg, |
60 | struct netlink_ext_ack *extack) | |
13d2a1d2 PM |
61 | { |
62 | struct drr_sched *q = qdisc_priv(sch); | |
63 | struct drr_class *cl = (struct drr_class *)*arg; | |
1844f747 | 64 | struct nlattr *opt = tca[TCA_OPTIONS]; |
13d2a1d2 PM |
65 | struct nlattr *tb[TCA_DRR_MAX + 1]; |
66 | u32 quantum; | |
67 | int err; | |
68 | ||
a7c31693 AA |
69 | if (!opt) { |
70 | NL_SET_ERR_MSG(extack, "DRR options are required for this operation"); | |
1844f747 | 71 | return -EINVAL; |
a7c31693 | 72 | } |
1844f747 | 73 | |
8cb08174 JB |
74 | err = nla_parse_nested_deprecated(tb, TCA_DRR_MAX, opt, drr_policy, |
75 | extack); | |
13d2a1d2 PM |
76 | if (err < 0) |
77 | return err; | |
78 | ||
79 | if (tb[TCA_DRR_QUANTUM]) { | |
80 | quantum = nla_get_u32(tb[TCA_DRR_QUANTUM]); | |
a7c31693 AA |
81 | if (quantum == 0) { |
82 | NL_SET_ERR_MSG(extack, "Specified DRR quantum cannot be zero"); | |
13d2a1d2 | 83 | return -EINVAL; |
a7c31693 | 84 | } |
13d2a1d2 PM |
85 | } else |
86 | quantum = psched_mtu(qdisc_dev(sch)); | |
87 | ||
88 | if (cl != NULL) { | |
71bcb09a | 89 | if (tca[TCA_RATE]) { |
22e0f8b9 JF |
90 | err = gen_replace_estimator(&cl->bstats, NULL, |
91 | &cl->rate_est, | |
29cbcd85 | 92 | NULL, true, |
71bcb09a | 93 | tca[TCA_RATE]); |
a7c31693 AA |
94 | if (err) { |
95 | NL_SET_ERR_MSG(extack, "Failed to replace estimator"); | |
71bcb09a | 96 | return err; |
a7c31693 | 97 | } |
71bcb09a SH |
98 | } |
99 | ||
13d2a1d2 PM |
100 | sch_tree_lock(sch); |
101 | if (tb[TCA_DRR_QUANTUM]) | |
102 | cl->quantum = quantum; | |
103 | sch_tree_unlock(sch); | |
104 | ||
13d2a1d2 PM |
105 | return 0; |
106 | } | |
107 | ||
108 | cl = kzalloc(sizeof(struct drr_class), GFP_KERNEL); | |
109 | if (cl == NULL) | |
110 | return -ENOBUFS; | |
111 | ||
50dc9a85 | 112 | gnet_stats_basic_sync_init(&cl->bstats); |
df008598 | 113 | INIT_LIST_HEAD(&cl->alist); |
13d2a1d2 PM |
114 | cl->common.classid = classid; |
115 | cl->quantum = quantum; | |
3511c913 | 116 | cl->qdisc = qdisc_create_dflt(sch->dev_queue, |
a38a9882 AA |
117 | &pfifo_qdisc_ops, classid, |
118 | NULL); | |
13d2a1d2 PM |
119 | if (cl->qdisc == NULL) |
120 | cl->qdisc = &noop_qdisc; | |
49b49971 JK |
121 | else |
122 | qdisc_hash_add(cl->qdisc, true); | |
13d2a1d2 | 123 | |
71bcb09a | 124 | if (tca[TCA_RATE]) { |
22e0f8b9 | 125 | err = gen_replace_estimator(&cl->bstats, NULL, &cl->rate_est, |
29cbcd85 | 126 | NULL, true, tca[TCA_RATE]); |
71bcb09a | 127 | if (err) { |
a7c31693 | 128 | NL_SET_ERR_MSG(extack, "Failed to replace estimator"); |
86bd446b | 129 | qdisc_put(cl->qdisc); |
71bcb09a SH |
130 | kfree(cl); |
131 | return err; | |
132 | } | |
133 | } | |
13d2a1d2 PM |
134 | |
135 | sch_tree_lock(sch); | |
136 | qdisc_class_hash_insert(&q->clhash, &cl->common); | |
137 | sch_tree_unlock(sch); | |
138 | ||
139 | qdisc_class_hash_grow(sch, &q->clhash); | |
140 | ||
141 | *arg = (unsigned long)cl; | |
142 | return 0; | |
143 | } | |
144 | ||
145 | static void drr_destroy_class(struct Qdisc *sch, struct drr_class *cl) | |
146 | { | |
1c0d32fd | 147 | gen_kill_estimator(&cl->rate_est); |
86bd446b | 148 | qdisc_put(cl->qdisc); |
13d2a1d2 PM |
149 | kfree(cl); |
150 | } | |
151 | ||
4dd78a73 MM |
152 | static int drr_delete_class(struct Qdisc *sch, unsigned long arg, |
153 | struct netlink_ext_ack *extack) | |
13d2a1d2 PM |
154 | { |
155 | struct drr_sched *q = qdisc_priv(sch); | |
156 | struct drr_class *cl = (struct drr_class *)arg; | |
157 | ||
daf8d918 PT |
158 | if (qdisc_class_in_use(&cl->common)) { |
159 | NL_SET_ERR_MSG(extack, "DRR class is in use"); | |
13d2a1d2 | 160 | return -EBUSY; |
daf8d918 | 161 | } |
13d2a1d2 PM |
162 | |
163 | sch_tree_lock(sch); | |
164 | ||
e5f0e8f8 | 165 | qdisc_purge_queue(cl->qdisc); |
13d2a1d2 PM |
166 | qdisc_class_hash_remove(&q->clhash, &cl->common); |
167 | ||
13d2a1d2 | 168 | sch_tree_unlock(sch); |
13d2a1d2 | 169 | |
143976ce WC |
170 | drr_destroy_class(sch, cl); |
171 | return 0; | |
13d2a1d2 PM |
172 | } |
173 | ||
143976ce | 174 | static unsigned long drr_search_class(struct Qdisc *sch, u32 classid) |
13d2a1d2 | 175 | { |
143976ce | 176 | return (unsigned long)drr_find_class(sch, classid); |
13d2a1d2 PM |
177 | } |
178 | ||
cbaacc4e AA |
179 | static struct tcf_block *drr_tcf_block(struct Qdisc *sch, unsigned long cl, |
180 | struct netlink_ext_ack *extack) | |
13d2a1d2 PM |
181 | { |
182 | struct drr_sched *q = qdisc_priv(sch); | |
183 | ||
a7c31693 AA |
184 | if (cl) { |
185 | NL_SET_ERR_MSG(extack, "DRR classid must be zero"); | |
13d2a1d2 | 186 | return NULL; |
a7c31693 | 187 | } |
13d2a1d2 | 188 | |
6529eaba | 189 | return q->block; |
13d2a1d2 PM |
190 | } |
191 | ||
192 | static unsigned long drr_bind_tcf(struct Qdisc *sch, unsigned long parent, | |
193 | u32 classid) | |
194 | { | |
195 | struct drr_class *cl = drr_find_class(sch, classid); | |
196 | ||
8798481b PT |
197 | if (cl) |
198 | qdisc_class_get(&cl->common); | |
13d2a1d2 PM |
199 | |
200 | return (unsigned long)cl; | |
201 | } | |
202 | ||
203 | static void drr_unbind_tcf(struct Qdisc *sch, unsigned long arg) | |
204 | { | |
205 | struct drr_class *cl = (struct drr_class *)arg; | |
206 | ||
8798481b | 207 | qdisc_class_put(&cl->common); |
13d2a1d2 PM |
208 | } |
209 | ||
210 | static int drr_graft_class(struct Qdisc *sch, unsigned long arg, | |
653d6fd6 AA |
211 | struct Qdisc *new, struct Qdisc **old, |
212 | struct netlink_ext_ack *extack) | |
13d2a1d2 PM |
213 | { |
214 | struct drr_class *cl = (struct drr_class *)arg; | |
215 | ||
216 | if (new == NULL) { | |
a38a9882 AA |
217 | new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops, |
218 | cl->common.classid, NULL); | |
13d2a1d2 PM |
219 | if (new == NULL) |
220 | new = &noop_qdisc; | |
221 | } | |
222 | ||
86a7996c | 223 | *old = qdisc_replace(sch, new, &cl->qdisc); |
13d2a1d2 PM |
224 | return 0; |
225 | } | |
226 | ||
227 | static struct Qdisc *drr_class_leaf(struct Qdisc *sch, unsigned long arg) | |
228 | { | |
229 | struct drr_class *cl = (struct drr_class *)arg; | |
230 | ||
231 | return cl->qdisc; | |
232 | } | |
233 | ||
234 | static void drr_qlen_notify(struct Qdisc *csh, unsigned long arg) | |
235 | { | |
236 | struct drr_class *cl = (struct drr_class *)arg; | |
237 | ||
df008598 | 238 | list_del_init(&cl->alist); |
13d2a1d2 PM |
239 | } |
240 | ||
241 | static int drr_dump_class(struct Qdisc *sch, unsigned long arg, | |
242 | struct sk_buff *skb, struct tcmsg *tcm) | |
243 | { | |
244 | struct drr_class *cl = (struct drr_class *)arg; | |
245 | struct nlattr *nest; | |
246 | ||
247 | tcm->tcm_parent = TC_H_ROOT; | |
248 | tcm->tcm_handle = cl->common.classid; | |
249 | tcm->tcm_info = cl->qdisc->handle; | |
250 | ||
ae0be8de | 251 | nest = nla_nest_start_noflag(skb, TCA_OPTIONS); |
13d2a1d2 PM |
252 | if (nest == NULL) |
253 | goto nla_put_failure; | |
1b34ec43 DM |
254 | if (nla_put_u32(skb, TCA_DRR_QUANTUM, cl->quantum)) |
255 | goto nla_put_failure; | |
13d2a1d2 PM |
256 | return nla_nest_end(skb, nest); |
257 | ||
258 | nla_put_failure: | |
259 | nla_nest_cancel(skb, nest); | |
260 | return -EMSGSIZE; | |
261 | } | |
262 | ||
263 | static int drr_dump_class_stats(struct Qdisc *sch, unsigned long arg, | |
264 | struct gnet_dump *d) | |
265 | { | |
266 | struct drr_class *cl = (struct drr_class *)arg; | |
5dd431b6 PA |
267 | __u32 qlen = qdisc_qlen_sum(cl->qdisc); |
268 | struct Qdisc *cl_q = cl->qdisc; | |
13d2a1d2 PM |
269 | struct tc_drr_stats xstats; |
270 | ||
271 | memset(&xstats, 0, sizeof(xstats)); | |
64015853 | 272 | if (qlen) |
13d2a1d2 PM |
273 | xstats.deficit = cl->deficit; |
274 | ||
29cbcd85 | 275 | if (gnet_stats_copy_basic(d, NULL, &cl->bstats, true) < 0 || |
1c0d32fd | 276 | gnet_stats_copy_rate_est(d, &cl->rate_est) < 0 || |
5dd431b6 | 277 | gnet_stats_copy_queue(d, cl_q->cpu_qstats, &cl_q->qstats, qlen) < 0) |
13d2a1d2 PM |
278 | return -1; |
279 | ||
280 | return gnet_stats_copy_app(d, &xstats, sizeof(xstats)); | |
281 | } | |
282 | ||
283 | static void drr_walk(struct Qdisc *sch, struct qdisc_walker *arg) | |
284 | { | |
285 | struct drr_sched *q = qdisc_priv(sch); | |
286 | struct drr_class *cl; | |
13d2a1d2 PM |
287 | unsigned int i; |
288 | ||
289 | if (arg->stop) | |
290 | return; | |
291 | ||
292 | for (i = 0; i < q->clhash.hashsize; i++) { | |
b67bfe0d | 293 | hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) { |
e046fa89 | 294 | if (!tc_qdisc_stats_dump(sch, (unsigned long)cl, arg)) |
13d2a1d2 | 295 | return; |
13d2a1d2 PM |
296 | } |
297 | } | |
298 | } | |
299 | ||
300 | static struct drr_class *drr_classify(struct sk_buff *skb, struct Qdisc *sch, | |
301 | int *qerr) | |
302 | { | |
303 | struct drr_sched *q = qdisc_priv(sch); | |
304 | struct drr_class *cl; | |
305 | struct tcf_result res; | |
25d8c0d5 | 306 | struct tcf_proto *fl; |
13d2a1d2 PM |
307 | int result; |
308 | ||
309 | if (TC_H_MAJ(skb->priority ^ sch->handle) == 0) { | |
310 | cl = drr_find_class(sch, skb->priority); | |
311 | if (cl != NULL) | |
312 | return cl; | |
313 | } | |
314 | ||
315 | *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS; | |
25d8c0d5 | 316 | fl = rcu_dereference_bh(q->filter_list); |
3aa26055 | 317 | result = tcf_classify(skb, NULL, fl, &res, false); |
13d2a1d2 PM |
318 | if (result >= 0) { |
319 | #ifdef CONFIG_NET_CLS_ACT | |
320 | switch (result) { | |
321 | case TC_ACT_QUEUED: | |
322 | case TC_ACT_STOLEN: | |
e25ea21f | 323 | case TC_ACT_TRAP: |
13d2a1d2 | 324 | *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN; |
964201de | 325 | fallthrough; |
13d2a1d2 PM |
326 | case TC_ACT_SHOT: |
327 | return NULL; | |
328 | } | |
329 | #endif | |
330 | cl = (struct drr_class *)res.class; | |
331 | if (cl == NULL) | |
332 | cl = drr_find_class(sch, res.classid); | |
333 | return cl; | |
334 | } | |
335 | return NULL; | |
336 | } | |
337 | ||
ac5c66f2 | 338 | static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch, |
520ac30f | 339 | struct sk_buff **to_free) |
13d2a1d2 | 340 | { |
f6bab199 | 341 | unsigned int len = qdisc_pkt_len(skb); |
13d2a1d2 PM |
342 | struct drr_sched *q = qdisc_priv(sch); |
343 | struct drr_class *cl; | |
f54ba779 | 344 | int err = 0; |
13d2a1d2 PM |
345 | |
346 | cl = drr_classify(skb, sch, &err); | |
347 | if (cl == NULL) { | |
348 | if (err & __NET_XMIT_BYPASS) | |
25331d6c | 349 | qdisc_qstats_drop(sch); |
520ac30f | 350 | __qdisc_drop(skb, to_free); |
13d2a1d2 PM |
351 | return err; |
352 | } | |
353 | ||
ac5c66f2 | 354 | err = qdisc_enqueue(skb, cl->qdisc, to_free); |
13d2a1d2 PM |
355 | if (unlikely(err != NET_XMIT_SUCCESS)) { |
356 | if (net_xmit_drop_count(err)) { | |
357 | cl->qstats.drops++; | |
25331d6c | 358 | qdisc_qstats_drop(sch); |
13d2a1d2 PM |
359 | } |
360 | return err; | |
361 | } | |
362 | ||
f99a3fbf | 363 | if (!cl_is_active(cl)) { |
13d2a1d2 PM |
364 | list_add_tail(&cl->alist, &q->active); |
365 | cl->deficit = cl->quantum; | |
366 | } | |
367 | ||
f6bab199 | 368 | sch->qstats.backlog += len; |
13d2a1d2 PM |
369 | sch->q.qlen++; |
370 | return err; | |
371 | } | |
372 | ||
373 | static struct sk_buff *drr_dequeue(struct Qdisc *sch) | |
374 | { | |
375 | struct drr_sched *q = qdisc_priv(sch); | |
376 | struct drr_class *cl; | |
377 | struct sk_buff *skb; | |
378 | unsigned int len; | |
379 | ||
3f0947c3 PM |
380 | if (list_empty(&q->active)) |
381 | goto out; | |
382 | while (1) { | |
13d2a1d2 PM |
383 | cl = list_first_entry(&q->active, struct drr_class, alist); |
384 | skb = cl->qdisc->ops->peek(cl->qdisc); | |
6e765a00 FW |
385 | if (skb == NULL) { |
386 | qdisc_warn_nonwc(__func__, cl->qdisc); | |
3f0947c3 | 387 | goto out; |
6e765a00 | 388 | } |
13d2a1d2 PM |
389 | |
390 | len = qdisc_pkt_len(skb); | |
391 | if (len <= cl->deficit) { | |
392 | cl->deficit -= len; | |
393 | skb = qdisc_dequeue_peeked(cl->qdisc); | |
df3eb6cd BH |
394 | if (unlikely(skb == NULL)) |
395 | goto out; | |
13d2a1d2 | 396 | if (cl->qdisc->q.qlen == 0) |
df008598 | 397 | list_del_init(&cl->alist); |
2dd875ff ED |
398 | |
399 | bstats_update(&cl->bstats, skb); | |
9190b3b3 | 400 | qdisc_bstats_update(sch, skb); |
6a73b571 | 401 | qdisc_qstats_backlog_dec(sch, skb); |
13d2a1d2 PM |
402 | sch->q.qlen--; |
403 | return skb; | |
404 | } | |
405 | ||
406 | cl->deficit += cl->quantum; | |
13d2a1d2 PM |
407 | list_move_tail(&cl->alist, &q->active); |
408 | } | |
3f0947c3 | 409 | out: |
13d2a1d2 PM |
410 | return NULL; |
411 | } | |
412 | ||
e63d7dfd AA |
413 | static int drr_init_qdisc(struct Qdisc *sch, struct nlattr *opt, |
414 | struct netlink_ext_ack *extack) | |
13d2a1d2 PM |
415 | { |
416 | struct drr_sched *q = qdisc_priv(sch); | |
417 | int err; | |
418 | ||
8d1a77f9 | 419 | err = tcf_block_get(&q->block, &q->filter_list, sch, extack); |
6529eaba JP |
420 | if (err) |
421 | return err; | |
13d2a1d2 PM |
422 | err = qdisc_class_hash_init(&q->clhash); |
423 | if (err < 0) | |
424 | return err; | |
425 | INIT_LIST_HEAD(&q->active); | |
426 | return 0; | |
427 | } | |
428 | ||
429 | static void drr_reset_qdisc(struct Qdisc *sch) | |
430 | { | |
431 | struct drr_sched *q = qdisc_priv(sch); | |
432 | struct drr_class *cl; | |
13d2a1d2 PM |
433 | unsigned int i; |
434 | ||
435 | for (i = 0; i < q->clhash.hashsize; i++) { | |
b67bfe0d | 436 | hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) { |
13d2a1d2 | 437 | if (cl->qdisc->q.qlen) |
df008598 | 438 | list_del_init(&cl->alist); |
13d2a1d2 PM |
439 | qdisc_reset(cl->qdisc); |
440 | } | |
441 | } | |
13d2a1d2 PM |
442 | } |
443 | ||
444 | static void drr_destroy_qdisc(struct Qdisc *sch) | |
445 | { | |
446 | struct drr_sched *q = qdisc_priv(sch); | |
447 | struct drr_class *cl; | |
b67bfe0d | 448 | struct hlist_node *next; |
13d2a1d2 PM |
449 | unsigned int i; |
450 | ||
6529eaba | 451 | tcf_block_put(q->block); |
13d2a1d2 PM |
452 | |
453 | for (i = 0; i < q->clhash.hashsize; i++) { | |
b67bfe0d | 454 | hlist_for_each_entry_safe(cl, next, &q->clhash.hash[i], |
13d2a1d2 PM |
455 | common.hnode) |
456 | drr_destroy_class(sch, cl); | |
457 | } | |
458 | qdisc_class_hash_destroy(&q->clhash); | |
459 | } | |
460 | ||
461 | static const struct Qdisc_class_ops drr_class_ops = { | |
462 | .change = drr_change_class, | |
463 | .delete = drr_delete_class, | |
143976ce | 464 | .find = drr_search_class, |
6529eaba | 465 | .tcf_block = drr_tcf_block, |
13d2a1d2 PM |
466 | .bind_tcf = drr_bind_tcf, |
467 | .unbind_tcf = drr_unbind_tcf, | |
468 | .graft = drr_graft_class, | |
469 | .leaf = drr_class_leaf, | |
470 | .qlen_notify = drr_qlen_notify, | |
471 | .dump = drr_dump_class, | |
472 | .dump_stats = drr_dump_class_stats, | |
473 | .walk = drr_walk, | |
474 | }; | |
475 | ||
476 | static struct Qdisc_ops drr_qdisc_ops __read_mostly = { | |
477 | .cl_ops = &drr_class_ops, | |
478 | .id = "drr", | |
479 | .priv_size = sizeof(struct drr_sched), | |
480 | .enqueue = drr_enqueue, | |
481 | .dequeue = drr_dequeue, | |
482 | .peek = qdisc_peek_dequeued, | |
13d2a1d2 PM |
483 | .init = drr_init_qdisc, |
484 | .reset = drr_reset_qdisc, | |
485 | .destroy = drr_destroy_qdisc, | |
486 | .owner = THIS_MODULE, | |
487 | }; | |
241a94ab | 488 | MODULE_ALIAS_NET_SCH("drr"); |
13d2a1d2 PM |
489 | |
490 | static int __init drr_init(void) | |
491 | { | |
492 | return register_qdisc(&drr_qdisc_ops); | |
493 | } | |
494 | ||
495 | static void __exit drr_exit(void) | |
496 | { | |
497 | unregister_qdisc(&drr_qdisc_ops); | |
498 | } | |
499 | ||
500 | module_init(drr_init); | |
501 | module_exit(drr_exit); | |
502 | MODULE_LICENSE("GPL"); | |
f96118c5 | 503 | MODULE_DESCRIPTION("Deficit Round Robin scheduler"); |