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1 | #ifndef __NET_SCHED_CODEL_H |
2 | #define __NET_SCHED_CODEL_H | |
3 | ||
4 | /* | |
5 | * Codel - The Controlled-Delay Active Queue Management algorithm | |
6 | * | |
7 | * Copyright (C) 2011-2012 Kathleen Nichols <nichols@pollere.com> | |
8 | * Copyright (C) 2011-2012 Van Jacobson <van@pollere.net> | |
9 | * Copyright (C) 2012 Michael D. Taht <dave.taht@bufferbloat.net> | |
10 | * Copyright (C) 2012 Eric Dumazet <edumazet@google.com> | |
11 | * | |
12 | * Redistribution and use in source and binary forms, with or without | |
13 | * modification, are permitted provided that the following conditions | |
14 | * are met: | |
15 | * 1. Redistributions of source code must retain the above copyright | |
16 | * notice, this list of conditions, and the following disclaimer, | |
17 | * without modification. | |
18 | * 2. Redistributions in binary form must reproduce the above copyright | |
19 | * notice, this list of conditions and the following disclaimer in the | |
20 | * documentation and/or other materials provided with the distribution. | |
21 | * 3. The names of the authors may not be used to endorse or promote products | |
22 | * derived from this software without specific prior written permission. | |
23 | * | |
24 | * Alternatively, provided that this notice is retained in full, this | |
25 | * software may be distributed under the terms of the GNU General | |
26 | * Public License ("GPL") version 2, in which case the provisions of the | |
27 | * GPL apply INSTEAD OF those given above. | |
28 | * | |
29 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
30 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
31 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |
32 | * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |
33 | * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
34 | * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |
35 | * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
36 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
37 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
38 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
39 | * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH | |
40 | * DAMAGE. | |
41 | * | |
42 | */ | |
43 | ||
44 | #include <linux/types.h> | |
45 | #include <linux/ktime.h> | |
46 | #include <linux/skbuff.h> | |
47 | #include <net/pkt_sched.h> | |
48 | #include <net/inet_ecn.h> | |
49 | ||
50 | /* Controlling Queue Delay (CoDel) algorithm | |
51 | * ========================================= | |
52 | * Source : Kathleen Nichols and Van Jacobson | |
53 | * http://queue.acm.org/detail.cfm?id=2209336 | |
54 | * | |
55 | * Implemented on linux by Dave Taht and Eric Dumazet | |
56 | */ | |
57 | ||
58 | ||
59 | /* CoDel uses a 1024 nsec clock, encoded in u32 | |
60 | * This gives a range of 2199 seconds, because of signed compares | |
61 | */ | |
62 | typedef u32 codel_time_t; | |
63 | typedef s32 codel_tdiff_t; | |
64 | #define CODEL_SHIFT 10 | |
65 | #define MS2TIME(a) ((a * NSEC_PER_MSEC) >> CODEL_SHIFT) | |
66 | ||
67 | static inline codel_time_t codel_get_time(void) | |
68 | { | |
69 | u64 ns = ktime_to_ns(ktime_get()); | |
70 | ||
71 | return ns >> CODEL_SHIFT; | |
72 | } | |
73 | ||
74 | #define codel_time_after(a, b) ((s32)(a) - (s32)(b) > 0) | |
75 | #define codel_time_after_eq(a, b) ((s32)(a) - (s32)(b) >= 0) | |
76 | #define codel_time_before(a, b) ((s32)(a) - (s32)(b) < 0) | |
77 | #define codel_time_before_eq(a, b) ((s32)(a) - (s32)(b) <= 0) | |
78 | ||
79 | /* Qdiscs using codel plugin must use codel_skb_cb in their own cb[] */ | |
80 | struct codel_skb_cb { | |
81 | codel_time_t enqueue_time; | |
82 | }; | |
83 | ||
84 | static struct codel_skb_cb *get_codel_cb(const struct sk_buff *skb) | |
85 | { | |
86 | qdisc_cb_private_validate(skb, sizeof(struct codel_skb_cb)); | |
87 | return (struct codel_skb_cb *)qdisc_skb_cb(skb)->data; | |
88 | } | |
89 | ||
90 | static codel_time_t codel_get_enqueue_time(const struct sk_buff *skb) | |
91 | { | |
92 | return get_codel_cb(skb)->enqueue_time; | |
93 | } | |
94 | ||
95 | static void codel_set_enqueue_time(struct sk_buff *skb) | |
96 | { | |
97 | get_codel_cb(skb)->enqueue_time = codel_get_time(); | |
98 | } | |
99 | ||
100 | static inline u32 codel_time_to_us(codel_time_t val) | |
101 | { | |
102 | u64 valns = ((u64)val << CODEL_SHIFT); | |
103 | ||
104 | do_div(valns, NSEC_PER_USEC); | |
105 | return (u32)valns; | |
106 | } | |
107 | ||
108 | /** | |
109 | * struct codel_params - contains codel parameters | |
110 | * @target: target queue size (in time units) | |
111 | * @interval: width of moving time window | |
112 | * @ecn: is Explicit Congestion Notification enabled | |
113 | */ | |
114 | struct codel_params { | |
115 | codel_time_t target; | |
116 | codel_time_t interval; | |
117 | bool ecn; | |
118 | }; | |
119 | ||
120 | /** | |
121 | * struct codel_vars - contains codel variables | |
122 | * @count: how many drops we've done since the last time we | |
123 | * entered dropping state | |
124 | * @lastcount: count at entry to dropping state | |
125 | * @dropping: set to true if in dropping state | |
126 | * @first_above_time: when we went (or will go) continuously above target | |
127 | * for interval | |
128 | * @drop_next: time to drop next packet, or when we dropped last | |
129 | * @ldelay: sojourn time of last dequeued packet | |
130 | */ | |
131 | struct codel_vars { | |
132 | u32 count; | |
133 | u32 lastcount; | |
134 | bool dropping; | |
135 | codel_time_t first_above_time; | |
136 | codel_time_t drop_next; | |
137 | codel_time_t ldelay; | |
138 | }; | |
139 | ||
140 | /** | |
141 | * struct codel_stats - contains codel shared variables and stats | |
142 | * @maxpacket: largest packet we've seen so far | |
143 | * @drop_count: temp count of dropped packets in dequeue() | |
144 | * ecn_mark: number of packets we ECN marked instead of dropping | |
145 | */ | |
146 | struct codel_stats { | |
147 | u32 maxpacket; | |
148 | u32 drop_count; | |
149 | u32 ecn_mark; | |
150 | }; | |
151 | ||
152 | static void codel_params_init(struct codel_params *params) | |
153 | { | |
154 | params->interval = MS2TIME(100); | |
155 | params->target = MS2TIME(5); | |
156 | params->ecn = false; | |
157 | } | |
158 | ||
159 | static void codel_vars_init(struct codel_vars *vars) | |
160 | { | |
161 | vars->drop_next = 0; | |
162 | vars->first_above_time = 0; | |
163 | vars->dropping = false; /* exit dropping state */ | |
164 | vars->count = 0; | |
165 | vars->lastcount = 0; | |
166 | } | |
167 | ||
168 | static void codel_stats_init(struct codel_stats *stats) | |
169 | { | |
170 | stats->maxpacket = 256; | |
171 | } | |
172 | ||
173 | /* return interval/sqrt(x) with good precision | |
174 | * relies on int_sqrt(unsigned long x) kernel implementation | |
175 | */ | |
176 | static u32 codel_inv_sqrt(u32 _interval, u32 _x) | |
177 | { | |
178 | u64 interval = _interval; | |
179 | unsigned long x = _x; | |
180 | ||
181 | /* Scale operands for max precision */ | |
182 | ||
183 | #if BITS_PER_LONG == 64 | |
184 | x <<= 32; /* On 64bit arches, we can prescale x by 32bits */ | |
185 | interval <<= 16; | |
186 | #endif | |
187 | ||
188 | while (x < (1UL << (BITS_PER_LONG - 2))) { | |
189 | x <<= 2; | |
190 | interval <<= 1; | |
191 | } | |
192 | do_div(interval, int_sqrt(x)); | |
193 | return (u32)interval; | |
194 | } | |
195 | ||
196 | static codel_time_t codel_control_law(codel_time_t t, | |
197 | codel_time_t interval, | |
198 | u32 count) | |
199 | { | |
200 | return t + codel_inv_sqrt(interval, count); | |
201 | } | |
202 | ||
203 | ||
204 | static bool codel_should_drop(struct sk_buff *skb, | |
205 | unsigned int *backlog, | |
206 | struct codel_vars *vars, | |
207 | struct codel_params *params, | |
208 | struct codel_stats *stats, | |
209 | codel_time_t now) | |
210 | { | |
211 | bool ok_to_drop; | |
212 | ||
213 | if (!skb) { | |
214 | vars->first_above_time = 0; | |
215 | return false; | |
216 | } | |
217 | ||
218 | vars->ldelay = now - codel_get_enqueue_time(skb); | |
219 | *backlog -= qdisc_pkt_len(skb); | |
220 | ||
221 | if (unlikely(qdisc_pkt_len(skb) > stats->maxpacket)) | |
222 | stats->maxpacket = qdisc_pkt_len(skb); | |
223 | ||
224 | if (codel_time_before(vars->ldelay, params->target) || | |
225 | *backlog <= stats->maxpacket) { | |
226 | /* went below - stay below for at least interval */ | |
227 | vars->first_above_time = 0; | |
228 | return false; | |
229 | } | |
230 | ok_to_drop = false; | |
231 | if (vars->first_above_time == 0) { | |
232 | /* just went above from below. If we stay above | |
233 | * for at least interval we'll say it's ok to drop | |
234 | */ | |
235 | vars->first_above_time = now + params->interval; | |
236 | } else if (codel_time_after(now, vars->first_above_time)) { | |
237 | ok_to_drop = true; | |
238 | } | |
239 | return ok_to_drop; | |
240 | } | |
241 | ||
242 | typedef struct sk_buff * (*codel_skb_dequeue_t)(struct codel_vars *vars, | |
243 | struct Qdisc *sch); | |
244 | ||
245 | static struct sk_buff *codel_dequeue(struct Qdisc *sch, | |
246 | struct codel_params *params, | |
247 | struct codel_vars *vars, | |
248 | struct codel_stats *stats, | |
249 | codel_skb_dequeue_t dequeue_func, | |
250 | u32 *backlog) | |
251 | { | |
252 | struct sk_buff *skb = dequeue_func(vars, sch); | |
253 | codel_time_t now; | |
254 | bool drop; | |
255 | ||
256 | if (!skb) { | |
257 | vars->dropping = false; | |
258 | return skb; | |
259 | } | |
260 | now = codel_get_time(); | |
261 | drop = codel_should_drop(skb, backlog, vars, params, stats, now); | |
262 | if (vars->dropping) { | |
263 | if (!drop) { | |
264 | /* sojourn time below target - leave dropping state */ | |
265 | vars->dropping = false; | |
266 | } else if (codel_time_after_eq(now, vars->drop_next)) { | |
267 | /* It's time for the next drop. Drop the current | |
268 | * packet and dequeue the next. The dequeue might | |
269 | * take us out of dropping state. | |
270 | * If not, schedule the next drop. | |
271 | * A large backlog might result in drop rates so high | |
272 | * that the next drop should happen now, | |
273 | * hence the while loop. | |
274 | */ | |
275 | while (vars->dropping && | |
276 | codel_time_after_eq(now, vars->drop_next)) { | |
277 | if (++vars->count == 0) /* avoid zero divides */ | |
278 | vars->count = ~0U; | |
279 | if (params->ecn && INET_ECN_set_ce(skb)) { | |
280 | stats->ecn_mark++; | |
281 | vars->drop_next = | |
282 | codel_control_law(vars->drop_next, | |
283 | params->interval, | |
284 | vars->count); | |
285 | goto end; | |
286 | } | |
287 | qdisc_drop(skb, sch); | |
288 | stats->drop_count++; | |
289 | skb = dequeue_func(vars, sch); | |
290 | if (!codel_should_drop(skb, backlog, | |
291 | vars, params, stats, now)) { | |
292 | /* leave dropping state */ | |
293 | vars->dropping = false; | |
294 | } else { | |
295 | /* and schedule the next drop */ | |
296 | vars->drop_next = | |
297 | codel_control_law(vars->drop_next, | |
298 | params->interval, | |
299 | vars->count); | |
300 | } | |
301 | } | |
302 | } | |
303 | } else if (drop) { | |
304 | if (params->ecn && INET_ECN_set_ce(skb)) { | |
305 | stats->ecn_mark++; | |
306 | } else { | |
307 | qdisc_drop(skb, sch); | |
308 | stats->drop_count++; | |
309 | ||
310 | skb = dequeue_func(vars, sch); | |
311 | drop = codel_should_drop(skb, backlog, vars, params, | |
312 | stats, now); | |
313 | } | |
314 | vars->dropping = true; | |
315 | /* if min went above target close to when we last went below it | |
316 | * assume that the drop rate that controlled the queue on the | |
317 | * last cycle is a good starting point to control it now. | |
318 | */ | |
319 | if (codel_time_before(now - vars->drop_next, | |
320 | 16 * params->interval)) { | |
321 | vars->count = (vars->count - vars->lastcount) | 1; | |
322 | } else { | |
323 | vars->count = 1; | |
324 | } | |
325 | vars->lastcount = vars->count; | |
326 | vars->drop_next = codel_control_law(now, params->interval, | |
327 | vars->count); | |
328 | } | |
329 | end: | |
330 | return skb; | |
331 | } | |
332 | #endif |