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Linux/net/sched/sch_codel.c

  1 /*
  2  * Codel - The Controlled-Delay Active Queue Management algorithm
  3  *
  4  *  Copyright (C) 2011-2012 Kathleen Nichols <nichols@pollere.com>
  5  *  Copyright (C) 2011-2012 Van Jacobson <van@pollere.net>
  6  *
  7  *  Implemented on linux by :
  8  *  Copyright (C) 2012 Michael D. Taht <dave.taht@bufferbloat.net>
  9  *  Copyright (C) 2012,2015 Eric Dumazet <edumazet@google.com>
 10  *
 11  * Redistribution and use in source and binary forms, with or without
 12  * modification, are permitted provided that the following conditions
 13  * are met:
 14  * 1. Redistributions of source code must retain the above copyright
 15  *    notice, this list of conditions, and the following disclaimer,
 16  *    without modification.
 17  * 2. Redistributions in binary form must reproduce the above copyright
 18  *    notice, this list of conditions and the following disclaimer in the
 19  *    documentation and/or other materials provided with the distribution.
 20  * 3. The names of the authors may not be used to endorse or promote products
 21  *    derived from this software without specific prior written permission.
 22  *
 23  * Alternatively, provided that this notice is retained in full, this
 24  * software may be distributed under the terms of the GNU General
 25  * Public License ("GPL") version 2, in which case the provisions of the
 26  * GPL apply INSTEAD OF those given above.
 27  *
 28  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 29  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 30  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 31  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 32  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 33  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 34  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 35  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 36  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 37  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 38  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 39  * DAMAGE.
 40  *
 41  */
 42 
 43 #include <linux/module.h>
 44 #include <linux/slab.h>
 45 #include <linux/types.h>
 46 #include <linux/kernel.h>
 47 #include <linux/errno.h>
 48 #include <linux/skbuff.h>
 49 #include <linux/prefetch.h>
 50 #include <net/pkt_sched.h>
 51 #include <net/codel.h>
 52 #include <net/codel_impl.h>
 53 #include <net/codel_qdisc.h>
 54 
 55 
 56 #define DEFAULT_CODEL_LIMIT 1000
 57 
 58 struct codel_sched_data {
 59         struct codel_params     params;
 60         struct codel_vars       vars;
 61         struct codel_stats      stats;
 62         u32                     drop_overlimit;
 63 };
 64 
 65 /* This is the specific function called from codel_dequeue()
 66  * to dequeue a packet from queue. Note: backlog is handled in
 67  * codel, we dont need to reduce it here.
 68  */
 69 static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx)
 70 {
 71         struct Qdisc *sch = ctx;
 72         struct sk_buff *skb = __skb_dequeue(&sch->q);
 73 
 74         if (skb)
 75                 sch->qstats.backlog -= qdisc_pkt_len(skb);
 76 
 77         prefetch(&skb->end); /* we'll need skb_shinfo() */
 78         return skb;
 79 }
 80 
 81 static void drop_func(struct sk_buff *skb, void *ctx)
 82 {
 83         struct Qdisc *sch = ctx;
 84 
 85         kfree_skb(skb);
 86         qdisc_qstats_drop(sch);
 87 }
 88 
 89 static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch)
 90 {
 91         struct codel_sched_data *q = qdisc_priv(sch);
 92         struct sk_buff *skb;
 93 
 94         skb = codel_dequeue(sch, &sch->qstats.backlog, &q->params, &q->vars,
 95                             &q->stats, qdisc_pkt_len, codel_get_enqueue_time,
 96                             drop_func, dequeue_func);
 97 
 98         /* We cant call qdisc_tree_reduce_backlog() if our qlen is 0,
 99          * or HTB crashes. Defer it for next round.
100          */
101         if (q->stats.drop_count && sch->q.qlen) {
102                 qdisc_tree_reduce_backlog(sch, q->stats.drop_count, q->stats.drop_len);
103                 q->stats.drop_count = 0;
104                 q->stats.drop_len = 0;
105         }
106         if (skb)
107                 qdisc_bstats_update(sch, skb);
108         return skb;
109 }
110 
111 static int codel_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
112                                struct sk_buff **to_free)
113 {
114         struct codel_sched_data *q;
115 
116         if (likely(qdisc_qlen(sch) < sch->limit)) {
117                 codel_set_enqueue_time(skb);
118                 return qdisc_enqueue_tail(skb, sch);
119         }
120         q = qdisc_priv(sch);
121         q->drop_overlimit++;
122         return qdisc_drop(skb, sch, to_free);
123 }
124 
125 static const struct nla_policy codel_policy[TCA_CODEL_MAX + 1] = {
126         [TCA_CODEL_TARGET]      = { .type = NLA_U32 },
127         [TCA_CODEL_LIMIT]       = { .type = NLA_U32 },
128         [TCA_CODEL_INTERVAL]    = { .type = NLA_U32 },
129         [TCA_CODEL_ECN]         = { .type = NLA_U32 },
130         [TCA_CODEL_CE_THRESHOLD]= { .type = NLA_U32 },
131 };
132 
133 static int codel_change(struct Qdisc *sch, struct nlattr *opt)
134 {
135         struct codel_sched_data *q = qdisc_priv(sch);
136         struct nlattr *tb[TCA_CODEL_MAX + 1];
137         unsigned int qlen, dropped = 0;
138         int err;
139 
140         if (!opt)
141                 return -EINVAL;
142 
143         err = nla_parse_nested(tb, TCA_CODEL_MAX, opt, codel_policy);
144         if (err < 0)
145                 return err;
146 
147         sch_tree_lock(sch);
148 
149         if (tb[TCA_CODEL_TARGET]) {
150                 u32 target = nla_get_u32(tb[TCA_CODEL_TARGET]);
151 
152                 q->params.target = ((u64)target * NSEC_PER_USEC) >> CODEL_SHIFT;
153         }
154 
155         if (tb[TCA_CODEL_CE_THRESHOLD]) {
156                 u64 val = nla_get_u32(tb[TCA_CODEL_CE_THRESHOLD]);
157 
158                 q->params.ce_threshold = (val * NSEC_PER_USEC) >> CODEL_SHIFT;
159         }
160 
161         if (tb[TCA_CODEL_INTERVAL]) {
162                 u32 interval = nla_get_u32(tb[TCA_CODEL_INTERVAL]);
163 
164                 q->params.interval = ((u64)interval * NSEC_PER_USEC) >> CODEL_SHIFT;
165         }
166 
167         if (tb[TCA_CODEL_LIMIT])
168                 sch->limit = nla_get_u32(tb[TCA_CODEL_LIMIT]);
169 
170         if (tb[TCA_CODEL_ECN])
171                 q->params.ecn = !!nla_get_u32(tb[TCA_CODEL_ECN]);
172 
173         qlen = sch->q.qlen;
174         while (sch->q.qlen > sch->limit) {
175                 struct sk_buff *skb = __skb_dequeue(&sch->q);
176 
177                 dropped += qdisc_pkt_len(skb);
178                 qdisc_qstats_backlog_dec(sch, skb);
179                 rtnl_qdisc_drop(skb, sch);
180         }
181         qdisc_tree_reduce_backlog(sch, qlen - sch->q.qlen, dropped);
182 
183         sch_tree_unlock(sch);
184         return 0;
185 }
186 
187 static int codel_init(struct Qdisc *sch, struct nlattr *opt)
188 {
189         struct codel_sched_data *q = qdisc_priv(sch);
190 
191         sch->limit = DEFAULT_CODEL_LIMIT;
192 
193         codel_params_init(&q->params);
194         codel_vars_init(&q->vars);
195         codel_stats_init(&q->stats);
196         q->params.mtu = psched_mtu(qdisc_dev(sch));
197 
198         if (opt) {
199                 int err = codel_change(sch, opt);
200 
201                 if (err)
202                         return err;
203         }
204 
205         if (sch->limit >= 1)
206                 sch->flags |= TCQ_F_CAN_BYPASS;
207         else
208                 sch->flags &= ~TCQ_F_CAN_BYPASS;
209 
210         return 0;
211 }
212 
213 static int codel_dump(struct Qdisc *sch, struct sk_buff *skb)
214 {
215         struct codel_sched_data *q = qdisc_priv(sch);
216         struct nlattr *opts;
217 
218         opts = nla_nest_start(skb, TCA_OPTIONS);
219         if (opts == NULL)
220                 goto nla_put_failure;
221 
222         if (nla_put_u32(skb, TCA_CODEL_TARGET,
223                         codel_time_to_us(q->params.target)) ||
224             nla_put_u32(skb, TCA_CODEL_LIMIT,
225                         sch->limit) ||
226             nla_put_u32(skb, TCA_CODEL_INTERVAL,
227                         codel_time_to_us(q->params.interval)) ||
228             nla_put_u32(skb, TCA_CODEL_ECN,
229                         q->params.ecn))
230                 goto nla_put_failure;
231         if (q->params.ce_threshold != CODEL_DISABLED_THRESHOLD &&
232             nla_put_u32(skb, TCA_CODEL_CE_THRESHOLD,
233                         codel_time_to_us(q->params.ce_threshold)))
234                 goto nla_put_failure;
235         return nla_nest_end(skb, opts);
236 
237 nla_put_failure:
238         nla_nest_cancel(skb, opts);
239         return -1;
240 }
241 
242 static int codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
243 {
244         const struct codel_sched_data *q = qdisc_priv(sch);
245         struct tc_codel_xstats st = {
246                 .maxpacket      = q->stats.maxpacket,
247                 .count          = q->vars.count,
248                 .lastcount      = q->vars.lastcount,
249                 .drop_overlimit = q->drop_overlimit,
250                 .ldelay         = codel_time_to_us(q->vars.ldelay),
251                 .dropping       = q->vars.dropping,
252                 .ecn_mark       = q->stats.ecn_mark,
253                 .ce_mark        = q->stats.ce_mark,
254         };
255 
256         if (q->vars.dropping) {
257                 codel_tdiff_t delta = q->vars.drop_next - codel_get_time();
258 
259                 if (delta >= 0)
260                         st.drop_next = codel_time_to_us(delta);
261                 else
262                         st.drop_next = -codel_time_to_us(-delta);
263         }
264 
265         return gnet_stats_copy_app(d, &st, sizeof(st));
266 }
267 
268 static void codel_reset(struct Qdisc *sch)
269 {
270         struct codel_sched_data *q = qdisc_priv(sch);
271 
272         qdisc_reset_queue(sch);
273         codel_vars_init(&q->vars);
274 }
275 
276 static struct Qdisc_ops codel_qdisc_ops __read_mostly = {
277         .id             =       "codel",
278         .priv_size      =       sizeof(struct codel_sched_data),
279 
280         .enqueue        =       codel_qdisc_enqueue,
281         .dequeue        =       codel_qdisc_dequeue,
282         .peek           =       qdisc_peek_dequeued,
283         .init           =       codel_init,
284         .reset          =       codel_reset,
285         .change         =       codel_change,
286         .dump           =       codel_dump,
287         .dump_stats     =       codel_dump_stats,
288         .owner          =       THIS_MODULE,
289 };
290 
291 static int __init codel_module_init(void)
292 {
293         return register_qdisc(&codel_qdisc_ops);
294 }
295 
296 static void __exit codel_module_exit(void)
297 {
298         unregister_qdisc(&codel_qdisc_ops);
299 }
300 
301 module_init(codel_module_init)
302 module_exit(codel_module_exit)
303 
304 MODULE_DESCRIPTION("Controlled Delay queue discipline");
305 MODULE_AUTHOR("Dave Taht");
306 MODULE_AUTHOR("Eric Dumazet");
307 MODULE_LICENSE("Dual BSD/GPL");
308 

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