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1 | /* | |
2 | * net/sched/gen_estimator.c Simple rate estimator. | |
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 | * Changes: | |
12 | * Jamal Hadi Salim - moved it to net/core and reshulfed | |
13 | * names to make it usable in general net subsystem. | |
14 | */ | |
15 | ||
16 | #include <asm/uaccess.h> | |
17 | #include <asm/system.h> | |
18 | #include <linux/bitops.h> | |
19 | #include <linux/module.h> | |
20 | #include <linux/types.h> | |
21 | #include <linux/kernel.h> | |
22 | #include <linux/jiffies.h> | |
23 | #include <linux/string.h> | |
24 | #include <linux/mm.h> | |
25 | #include <linux/socket.h> | |
26 | #include <linux/sockios.h> | |
27 | #include <linux/in.h> | |
28 | #include <linux/errno.h> | |
29 | #include <linux/interrupt.h> | |
30 | #include <linux/netdevice.h> | |
31 | #include <linux/skbuff.h> | |
32 | #include <linux/rtnetlink.h> | |
33 | #include <linux/init.h> | |
34 | #include <linux/rbtree.h> | |
35 | #include <linux/slab.h> | |
36 | #include <net/sock.h> | |
37 | #include <net/gen_stats.h> | |
38 | ||
39 | /* | |
40 | This code is NOT intended to be used for statistics collection, | |
41 | its purpose is to provide a base for statistical multiplexing | |
42 | for controlled load service. | |
43 | If you need only statistics, run a user level daemon which | |
44 | periodically reads byte counters. | |
45 | ||
46 | Unfortunately, rate estimation is not a very easy task. | |
47 | F.e. I did not find a simple way to estimate the current peak rate | |
48 | and even failed to formulate the problem 8)8) | |
49 | ||
50 | So I preferred not to built an estimator into the scheduler, | |
51 | but run this task separately. | |
52 | Ideally, it should be kernel thread(s), but for now it runs | |
53 | from timers, which puts apparent top bounds on the number of rated | |
54 | flows, has minimal overhead on small, but is enough | |
55 | to handle controlled load service, sets of aggregates. | |
56 | ||
57 | We measure rate over A=(1<<interval) seconds and evaluate EWMA: | |
58 | ||
59 | avrate = avrate*(1-W) + rate*W | |
60 | ||
61 | where W is chosen as negative power of 2: W = 2^(-ewma_log) | |
62 | ||
63 | The resulting time constant is: | |
64 | ||
65 | T = A/(-ln(1-W)) | |
66 | ||
67 | ||
68 | NOTES. | |
69 | ||
70 | * avbps is scaled by 2^5, avpps is scaled by 2^10. | |
71 | * both values are reported as 32 bit unsigned values. bps can | |
72 | overflow for fast links : max speed being 34360Mbit/sec | |
73 | * Minimal interval is HZ/4=250msec (it is the greatest common divisor | |
74 | for HZ=100 and HZ=1024 8)), maximal interval | |
75 | is (HZ*2^EST_MAX_INTERVAL)/4 = 8sec. Shorter intervals | |
76 | are too expensive, longer ones can be implemented | |
77 | at user level painlessly. | |
78 | */ | |
79 | ||
80 | #define EST_MAX_INTERVAL 5 | |
81 | ||
82 | struct gen_estimator | |
83 | { | |
84 | struct list_head list; | |
85 | struct gnet_stats_basic_packed *bstats; | |
86 | struct gnet_stats_rate_est *rate_est; | |
87 | spinlock_t *stats_lock; | |
88 | int ewma_log; | |
89 | u64 last_bytes; | |
90 | u64 avbps; | |
91 | u32 last_packets; | |
92 | u32 avpps; | |
93 | struct rcu_head e_rcu; | |
94 | struct rb_node node; | |
95 | }; | |
96 | ||
97 | struct gen_estimator_head | |
98 | { | |
99 | struct timer_list timer; | |
100 | struct list_head list; | |
101 | }; | |
102 | ||
103 | static struct gen_estimator_head elist[EST_MAX_INTERVAL+1]; | |
104 | ||
105 | /* Protects against NULL dereference */ | |
106 | static DEFINE_RWLOCK(est_lock); | |
107 | ||
108 | /* Protects against soft lockup during large deletion */ | |
109 | static struct rb_root est_root = RB_ROOT; | |
110 | static DEFINE_SPINLOCK(est_tree_lock); | |
111 | ||
112 | static void est_timer(unsigned long arg) | |
113 | { | |
114 | int idx = (int)arg; | |
115 | struct gen_estimator *e; | |
116 | ||
117 | rcu_read_lock(); | |
118 | list_for_each_entry_rcu(e, &elist[idx].list, list) { | |
119 | u64 nbytes; | |
120 | u64 brate; | |
121 | u32 npackets; | |
122 | u32 rate; | |
123 | ||
124 | spin_lock(e->stats_lock); | |
125 | read_lock(&est_lock); | |
126 | if (e->bstats == NULL) | |
127 | goto skip; | |
128 | ||
129 | nbytes = e->bstats->bytes; | |
130 | npackets = e->bstats->packets; | |
131 | brate = (nbytes - e->last_bytes)<<(7 - idx); | |
132 | e->last_bytes = nbytes; | |
133 | e->avbps += (brate >> e->ewma_log) - (e->avbps >> e->ewma_log); | |
134 | e->rate_est->bps = (e->avbps+0xF)>>5; | |
135 | ||
136 | rate = (npackets - e->last_packets)<<(12 - idx); | |
137 | e->last_packets = npackets; | |
138 | e->avpps += (rate >> e->ewma_log) - (e->avpps >> e->ewma_log); | |
139 | e->rate_est->pps = (e->avpps+0x1FF)>>10; | |
140 | skip: | |
141 | read_unlock(&est_lock); | |
142 | spin_unlock(e->stats_lock); | |
143 | } | |
144 | ||
145 | if (!list_empty(&elist[idx].list)) | |
146 | mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx)); | |
147 | rcu_read_unlock(); | |
148 | } | |
149 | ||
150 | static void gen_add_node(struct gen_estimator *est) | |
151 | { | |
152 | struct rb_node **p = &est_root.rb_node, *parent = NULL; | |
153 | ||
154 | while (*p) { | |
155 | struct gen_estimator *e; | |
156 | ||
157 | parent = *p; | |
158 | e = rb_entry(parent, struct gen_estimator, node); | |
159 | ||
160 | if (est->bstats > e->bstats) | |
161 | p = &parent->rb_right; | |
162 | else | |
163 | p = &parent->rb_left; | |
164 | } | |
165 | rb_link_node(&est->node, parent, p); | |
166 | rb_insert_color(&est->node, &est_root); | |
167 | } | |
168 | ||
169 | static | |
170 | struct gen_estimator *gen_find_node(const struct gnet_stats_basic_packed *bstats, | |
171 | const struct gnet_stats_rate_est *rate_est) | |
172 | { | |
173 | struct rb_node *p = est_root.rb_node; | |
174 | ||
175 | while (p) { | |
176 | struct gen_estimator *e; | |
177 | ||
178 | e = rb_entry(p, struct gen_estimator, node); | |
179 | ||
180 | if (bstats > e->bstats) | |
181 | p = p->rb_right; | |
182 | else if (bstats < e->bstats || rate_est != e->rate_est) | |
183 | p = p->rb_left; | |
184 | else | |
185 | return e; | |
186 | } | |
187 | return NULL; | |
188 | } | |
189 | ||
190 | /** | |
191 | * gen_new_estimator - create a new rate estimator | |
192 | * @bstats: basic statistics | |
193 | * @rate_est: rate estimator statistics | |
194 | * @stats_lock: statistics lock | |
195 | * @opt: rate estimator configuration TLV | |
196 | * | |
197 | * Creates a new rate estimator with &bstats as source and &rate_est | |
198 | * as destination. A new timer with the interval specified in the | |
199 | * configuration TLV is created. Upon each interval, the latest statistics | |
200 | * will be read from &bstats and the estimated rate will be stored in | |
201 | * &rate_est with the statistics lock grabed during this period. | |
202 | * | |
203 | * Returns 0 on success or a negative error code. | |
204 | * | |
205 | */ | |
206 | int gen_new_estimator(struct gnet_stats_basic_packed *bstats, | |
207 | struct gnet_stats_rate_est *rate_est, | |
208 | spinlock_t *stats_lock, | |
209 | struct nlattr *opt) | |
210 | { | |
211 | struct gen_estimator *est; | |
212 | struct gnet_estimator *parm = nla_data(opt); | |
213 | int idx; | |
214 | ||
215 | if (nla_len(opt) < sizeof(*parm)) | |
216 | return -EINVAL; | |
217 | ||
218 | if (parm->interval < -2 || parm->interval > 3) | |
219 | return -EINVAL; | |
220 | ||
221 | est = kzalloc(sizeof(*est), GFP_KERNEL); | |
222 | if (est == NULL) | |
223 | return -ENOBUFS; | |
224 | ||
225 | idx = parm->interval + 2; | |
226 | est->bstats = bstats; | |
227 | est->rate_est = rate_est; | |
228 | est->stats_lock = stats_lock; | |
229 | est->ewma_log = parm->ewma_log; | |
230 | est->last_bytes = bstats->bytes; | |
231 | est->avbps = rate_est->bps<<5; | |
232 | est->last_packets = bstats->packets; | |
233 | est->avpps = rate_est->pps<<10; | |
234 | ||
235 | spin_lock_bh(&est_tree_lock); | |
236 | if (!elist[idx].timer.function) { | |
237 | INIT_LIST_HEAD(&elist[idx].list); | |
238 | setup_timer(&elist[idx].timer, est_timer, idx); | |
239 | } | |
240 | ||
241 | if (list_empty(&elist[idx].list)) | |
242 | mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx)); | |
243 | ||
244 | list_add_rcu(&est->list, &elist[idx].list); | |
245 | gen_add_node(est); | |
246 | spin_unlock_bh(&est_tree_lock); | |
247 | ||
248 | return 0; | |
249 | } | |
250 | EXPORT_SYMBOL(gen_new_estimator); | |
251 | ||
252 | /** | |
253 | * gen_kill_estimator - remove a rate estimator | |
254 | * @bstats: basic statistics | |
255 | * @rate_est: rate estimator statistics | |
256 | * | |
257 | * Removes the rate estimator specified by &bstats and &rate_est. | |
258 | * | |
259 | * Note : Caller should respect an RCU grace period before freeing stats_lock | |
260 | */ | |
261 | void gen_kill_estimator(struct gnet_stats_basic_packed *bstats, | |
262 | struct gnet_stats_rate_est *rate_est) | |
263 | { | |
264 | struct gen_estimator *e; | |
265 | ||
266 | spin_lock_bh(&est_tree_lock); | |
267 | while ((e = gen_find_node(bstats, rate_est))) { | |
268 | rb_erase(&e->node, &est_root); | |
269 | ||
270 | write_lock(&est_lock); | |
271 | e->bstats = NULL; | |
272 | write_unlock(&est_lock); | |
273 | ||
274 | list_del_rcu(&e->list); | |
275 | kfree_rcu(e, e_rcu); | |
276 | } | |
277 | spin_unlock_bh(&est_tree_lock); | |
278 | } | |
279 | EXPORT_SYMBOL(gen_kill_estimator); | |
280 | ||
281 | /** | |
282 | * gen_replace_estimator - replace rate estimator configuration | |
283 | * @bstats: basic statistics | |
284 | * @rate_est: rate estimator statistics | |
285 | * @stats_lock: statistics lock | |
286 | * @opt: rate estimator configuration TLV | |
287 | * | |
288 | * Replaces the configuration of a rate estimator by calling | |
289 | * gen_kill_estimator() and gen_new_estimator(). | |
290 | * | |
291 | * Returns 0 on success or a negative error code. | |
292 | */ | |
293 | int gen_replace_estimator(struct gnet_stats_basic_packed *bstats, | |
294 | struct gnet_stats_rate_est *rate_est, | |
295 | spinlock_t *stats_lock, struct nlattr *opt) | |
296 | { | |
297 | gen_kill_estimator(bstats, rate_est); | |
298 | return gen_new_estimator(bstats, rate_est, stats_lock, opt); | |
299 | } | |
300 | EXPORT_SYMBOL(gen_replace_estimator); | |
301 | ||
302 | /** | |
303 | * gen_estimator_active - test if estimator is currently in use | |
304 | * @bstats: basic statistics | |
305 | * @rate_est: rate estimator statistics | |
306 | * | |
307 | * Returns true if estimator is active, and false if not. | |
308 | */ | |
309 | bool gen_estimator_active(const struct gnet_stats_basic_packed *bstats, | |
310 | const struct gnet_stats_rate_est *rate_est) | |
311 | { | |
312 | bool res; | |
313 | ||
314 | ASSERT_RTNL(); | |
315 | ||
316 | spin_lock_bh(&est_tree_lock); | |
317 | res = gen_find_node(bstats, rate_est) != NULL; | |
318 | spin_unlock_bh(&est_tree_lock); | |
319 | ||
320 | return res; | |
321 | } | |
322 | EXPORT_SYMBOL(gen_estimator_active); |