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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * net/sched/gen_estimator.c Simple rate estimator.
4 *
5 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
6 * Eric Dumazet <edumazet@google.com>
7 *
8 * Changes:
9 * Jamal Hadi Salim - moved it to net/core and reshulfed
10 * names to make it usable in general net subsystem.
11 */
12
13#include <linux/uaccess.h>
14#include <linux/bitops.h>
15#include <linux/module.h>
16#include <linux/types.h>
17#include <linux/kernel.h>
18#include <linux/jiffies.h>
19#include <linux/string.h>
20#include <linux/mm.h>
21#include <linux/socket.h>
22#include <linux/sockios.h>
23#include <linux/in.h>
24#include <linux/errno.h>
25#include <linux/interrupt.h>
26#include <linux/netdevice.h>
27#include <linux/skbuff.h>
28#include <linux/rtnetlink.h>
29#include <linux/init.h>
30#include <linux/slab.h>
31#include <linux/seqlock.h>
32#include <net/sock.h>
33#include <net/gen_stats.h>
34
35/* This code is NOT intended to be used for statistics collection,
36 * its purpose is to provide a base for statistical multiplexing
37 * for controlled load service.
38 * If you need only statistics, run a user level daemon which
39 * periodically reads byte counters.
40 */
41
42struct net_rate_estimator {
43 struct gnet_stats_basic_sync *bstats;
44 spinlock_t *stats_lock;
45 bool running;
46 struct gnet_stats_basic_sync __percpu *cpu_bstats;
47 u8 ewma_log;
48 u8 intvl_log; /* period : (250ms << intvl_log) */
49
50 seqcount_t seq;
51 u64 last_packets;
52 u64 last_bytes;
53
54 u64 avpps;
55 u64 avbps;
56
57 unsigned long next_jiffies;
58 struct timer_list timer;
59 struct rcu_head rcu;
60};
61
62static void est_fetch_counters(struct net_rate_estimator *e,
63 struct gnet_stats_basic_sync *b)
64{
65 gnet_stats_basic_sync_init(b);
66 if (e->stats_lock)
67 spin_lock(e->stats_lock);
68
69 gnet_stats_add_basic(b, e->cpu_bstats, e->bstats, e->running);
70
71 if (e->stats_lock)
72 spin_unlock(e->stats_lock);
73
74}
75
76static void est_timer(struct timer_list *t)
77{
78 struct net_rate_estimator *est = from_timer(est, t, timer);
79 struct gnet_stats_basic_sync b;
80 u64 b_bytes, b_packets;
81 u64 rate, brate;
82
83 est_fetch_counters(est, &b);
84 b_bytes = u64_stats_read(&b.bytes);
85 b_packets = u64_stats_read(&b.packets);
86
87 brate = (b_bytes - est->last_bytes) << (10 - est->intvl_log);
88 brate = (brate >> est->ewma_log) - (est->avbps >> est->ewma_log);
89
90 rate = (b_packets - est->last_packets) << (10 - est->intvl_log);
91 rate = (rate >> est->ewma_log) - (est->avpps >> est->ewma_log);
92
93 write_seqcount_begin(&est->seq);
94 est->avbps += brate;
95 est->avpps += rate;
96 write_seqcount_end(&est->seq);
97
98 est->last_bytes = b_bytes;
99 est->last_packets = b_packets;
100
101 est->next_jiffies += ((HZ/4) << est->intvl_log);
102
103 if (unlikely(time_after_eq(jiffies, est->next_jiffies))) {
104 /* Ouch... timer was delayed. */
105 est->next_jiffies = jiffies + 1;
106 }
107 mod_timer(&est->timer, est->next_jiffies);
108}
109
110/**
111 * gen_new_estimator - create a new rate estimator
112 * @bstats: basic statistics
113 * @cpu_bstats: bstats per cpu
114 * @rate_est: rate estimator statistics
115 * @lock: lock for statistics and control path
116 * @running: true if @bstats represents a running qdisc, thus @bstats'
117 * internal values might change during basic reads. Only used
118 * if @bstats_cpu is NULL
119 * @opt: rate estimator configuration TLV
120 *
121 * Creates a new rate estimator with &bstats as source and &rate_est
122 * as destination. A new timer with the interval specified in the
123 * configuration TLV is created. Upon each interval, the latest statistics
124 * will be read from &bstats and the estimated rate will be stored in
125 * &rate_est with the statistics lock grabbed during this period.
126 *
127 * Returns 0 on success or a negative error code.
128 *
129 */
130int gen_new_estimator(struct gnet_stats_basic_sync *bstats,
131 struct gnet_stats_basic_sync __percpu *cpu_bstats,
132 struct net_rate_estimator __rcu **rate_est,
133 spinlock_t *lock,
134 bool running,
135 struct nlattr *opt)
136{
137 struct gnet_estimator *parm = nla_data(opt);
138 struct net_rate_estimator *old, *est;
139 struct gnet_stats_basic_sync b;
140 int intvl_log;
141
142 if (nla_len(opt) < sizeof(*parm))
143 return -EINVAL;
144
145 /* allowed timer periods are :
146 * -2 : 250ms, -1 : 500ms, 0 : 1 sec
147 * 1 : 2 sec, 2 : 4 sec, 3 : 8 sec
148 */
149 if (parm->interval < -2 || parm->interval > 3)
150 return -EINVAL;
151
152 if (parm->ewma_log == 0 || parm->ewma_log >= 31)
153 return -EINVAL;
154
155 est = kzalloc(sizeof(*est), GFP_KERNEL);
156 if (!est)
157 return -ENOBUFS;
158
159 seqcount_init(&est->seq);
160 intvl_log = parm->interval + 2;
161 est->bstats = bstats;
162 est->stats_lock = lock;
163 est->running = running;
164 est->ewma_log = parm->ewma_log;
165 est->intvl_log = intvl_log;
166 est->cpu_bstats = cpu_bstats;
167
168 if (lock)
169 local_bh_disable();
170 est_fetch_counters(est, &b);
171 if (lock)
172 local_bh_enable();
173 est->last_bytes = u64_stats_read(&b.bytes);
174 est->last_packets = u64_stats_read(&b.packets);
175
176 if (lock)
177 spin_lock_bh(lock);
178 old = rcu_dereference_protected(*rate_est, 1);
179 if (old) {
180 del_timer_sync(&old->timer);
181 est->avbps = old->avbps;
182 est->avpps = old->avpps;
183 }
184
185 est->next_jiffies = jiffies + ((HZ/4) << intvl_log);
186 timer_setup(&est->timer, est_timer, 0);
187 mod_timer(&est->timer, est->next_jiffies);
188
189 rcu_assign_pointer(*rate_est, est);
190 if (lock)
191 spin_unlock_bh(lock);
192 if (old)
193 kfree_rcu(old, rcu);
194 return 0;
195}
196EXPORT_SYMBOL(gen_new_estimator);
197
198/**
199 * gen_kill_estimator - remove a rate estimator
200 * @rate_est: rate estimator
201 *
202 * Removes the rate estimator.
203 *
204 */
205void gen_kill_estimator(struct net_rate_estimator __rcu **rate_est)
206{
207 struct net_rate_estimator *est;
208
209 est = unrcu_pointer(xchg(rate_est, NULL));
210 if (est) {
211 timer_shutdown_sync(&est->timer);
212 kfree_rcu(est, rcu);
213 }
214}
215EXPORT_SYMBOL(gen_kill_estimator);
216
217/**
218 * gen_replace_estimator - replace rate estimator configuration
219 * @bstats: basic statistics
220 * @cpu_bstats: bstats per cpu
221 * @rate_est: rate estimator statistics
222 * @lock: lock for statistics and control path
223 * @running: true if @bstats represents a running qdisc, thus @bstats'
224 * internal values might change during basic reads. Only used
225 * if @cpu_bstats is NULL
226 * @opt: rate estimator configuration TLV
227 *
228 * Replaces the configuration of a rate estimator by calling
229 * gen_kill_estimator() and gen_new_estimator().
230 *
231 * Returns 0 on success or a negative error code.
232 */
233int gen_replace_estimator(struct gnet_stats_basic_sync *bstats,
234 struct gnet_stats_basic_sync __percpu *cpu_bstats,
235 struct net_rate_estimator __rcu **rate_est,
236 spinlock_t *lock,
237 bool running, struct nlattr *opt)
238{
239 return gen_new_estimator(bstats, cpu_bstats, rate_est,
240 lock, running, opt);
241}
242EXPORT_SYMBOL(gen_replace_estimator);
243
244/**
245 * gen_estimator_active - test if estimator is currently in use
246 * @rate_est: rate estimator
247 *
248 * Returns true if estimator is active, and false if not.
249 */
250bool gen_estimator_active(struct net_rate_estimator __rcu **rate_est)
251{
252 return !!rcu_access_pointer(*rate_est);
253}
254EXPORT_SYMBOL(gen_estimator_active);
255
256bool gen_estimator_read(struct net_rate_estimator __rcu **rate_est,
257 struct gnet_stats_rate_est64 *sample)
258{
259 struct net_rate_estimator *est;
260 unsigned seq;
261
262 rcu_read_lock();
263 est = rcu_dereference(*rate_est);
264 if (!est) {
265 rcu_read_unlock();
266 return false;
267 }
268
269 do {
270 seq = read_seqcount_begin(&est->seq);
271 sample->bps = est->avbps >> 8;
272 sample->pps = est->avpps >> 8;
273 } while (read_seqcount_retry(&est->seq, seq));
274
275 rcu_read_unlock();
276 return true;
277}
278EXPORT_SYMBOL(gen_estimator_read);
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 <linux/bitops.h>
18#include <linux/module.h>
19#include <linux/types.h>
20#include <linux/kernel.h>
21#include <linux/jiffies.h>
22#include <linux/string.h>
23#include <linux/mm.h>
24#include <linux/socket.h>
25#include <linux/sockios.h>
26#include <linux/in.h>
27#include <linux/errno.h>
28#include <linux/interrupt.h>
29#include <linux/netdevice.h>
30#include <linux/skbuff.h>
31#include <linux/rtnetlink.h>
32#include <linux/init.h>
33#include <linux/rbtree.h>
34#include <linux/slab.h>
35#include <net/sock.h>
36#include <net/gen_stats.h>
37
38/*
39 This code is NOT intended to be used for statistics collection,
40 its purpose is to provide a base for statistical multiplexing
41 for controlled load service.
42 If you need only statistics, run a user level daemon which
43 periodically reads byte counters.
44
45 Unfortunately, rate estimation is not a very easy task.
46 F.e. I did not find a simple way to estimate the current peak rate
47 and even failed to formulate the problem 8)8)
48
49 So I preferred not to built an estimator into the scheduler,
50 but run this task separately.
51 Ideally, it should be kernel thread(s), but for now it runs
52 from timers, which puts apparent top bounds on the number of rated
53 flows, has minimal overhead on small, but is enough
54 to handle controlled load service, sets of aggregates.
55
56 We measure rate over A=(1<<interval) seconds and evaluate EWMA:
57
58 avrate = avrate*(1-W) + rate*W
59
60 where W is chosen as negative power of 2: W = 2^(-ewma_log)
61
62 The resulting time constant is:
63
64 T = A/(-ln(1-W))
65
66
67 NOTES.
68
69 * avbps and avpps are scaled by 2^5.
70 * both values are reported as 32 bit unsigned values. bps can
71 overflow for fast links : max speed being 34360Mbit/sec
72 * Minimal interval is HZ/4=250msec (it is the greatest common divisor
73 for HZ=100 and HZ=1024 8)), maximal interval
74 is (HZ*2^EST_MAX_INTERVAL)/4 = 8sec. Shorter intervals
75 are too expensive, longer ones can be implemented
76 at user level painlessly.
77 */
78
79#define EST_MAX_INTERVAL 5
80
81struct gen_estimator
82{
83 struct list_head list;
84 struct gnet_stats_basic_packed *bstats;
85 struct gnet_stats_rate_est64 *rate_est;
86 spinlock_t *stats_lock;
87 int ewma_log;
88 u32 last_packets;
89 unsigned long avpps;
90 u64 last_bytes;
91 u64 avbps;
92 struct rcu_head e_rcu;
93 struct rb_node node;
94 struct gnet_stats_basic_cpu __percpu *cpu_bstats;
95 struct rcu_head head;
96};
97
98struct gen_estimator_head
99{
100 struct timer_list timer;
101 struct list_head list;
102};
103
104static struct gen_estimator_head elist[EST_MAX_INTERVAL+1];
105
106/* Protects against NULL dereference */
107static DEFINE_RWLOCK(est_lock);
108
109/* Protects against soft lockup during large deletion */
110static struct rb_root est_root = RB_ROOT;
111static DEFINE_SPINLOCK(est_tree_lock);
112
113static void est_timer(unsigned long arg)
114{
115 int idx = (int)arg;
116 struct gen_estimator *e;
117
118 rcu_read_lock();
119 list_for_each_entry_rcu(e, &elist[idx].list, list) {
120 struct gnet_stats_basic_packed b = {0};
121 unsigned long rate;
122 u64 brate;
123
124 spin_lock(e->stats_lock);
125 read_lock(&est_lock);
126 if (e->bstats == NULL)
127 goto skip;
128
129 __gnet_stats_copy_basic(&b, e->cpu_bstats, e->bstats);
130
131 brate = (b.bytes - e->last_bytes)<<(7 - idx);
132 e->last_bytes = b.bytes;
133 e->avbps += (brate >> e->ewma_log) - (e->avbps >> e->ewma_log);
134 e->rate_est->bps = (e->avbps+0xF)>>5;
135
136 rate = b.packets - e->last_packets;
137 rate <<= (7 - idx);
138 e->last_packets = b.packets;
139 e->avpps += (rate >> e->ewma_log) - (e->avpps >> e->ewma_log);
140 e->rate_est->pps = (e->avpps + 0xF) >> 5;
141skip:
142 read_unlock(&est_lock);
143 spin_unlock(e->stats_lock);
144 }
145
146 if (!list_empty(&elist[idx].list))
147 mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx));
148 rcu_read_unlock();
149}
150
151static void gen_add_node(struct gen_estimator *est)
152{
153 struct rb_node **p = &est_root.rb_node, *parent = NULL;
154
155 while (*p) {
156 struct gen_estimator *e;
157
158 parent = *p;
159 e = rb_entry(parent, struct gen_estimator, node);
160
161 if (est->bstats > e->bstats)
162 p = &parent->rb_right;
163 else
164 p = &parent->rb_left;
165 }
166 rb_link_node(&est->node, parent, p);
167 rb_insert_color(&est->node, &est_root);
168}
169
170static
171struct gen_estimator *gen_find_node(const struct gnet_stats_basic_packed *bstats,
172 const struct gnet_stats_rate_est64 *rate_est)
173{
174 struct rb_node *p = est_root.rb_node;
175
176 while (p) {
177 struct gen_estimator *e;
178
179 e = rb_entry(p, struct gen_estimator, node);
180
181 if (bstats > e->bstats)
182 p = p->rb_right;
183 else if (bstats < e->bstats || rate_est != e->rate_est)
184 p = p->rb_left;
185 else
186 return e;
187 }
188 return NULL;
189}
190
191/**
192 * gen_new_estimator - create a new rate estimator
193 * @bstats: basic statistics
194 * @cpu_bstats: bstats per cpu
195 * @rate_est: rate estimator statistics
196 * @stats_lock: statistics lock
197 * @opt: rate estimator configuration TLV
198 *
199 * Creates a new rate estimator with &bstats as source and &rate_est
200 * as destination. A new timer with the interval specified in the
201 * configuration TLV is created. Upon each interval, the latest statistics
202 * will be read from &bstats and the estimated rate will be stored in
203 * &rate_est with the statistics lock grabbed during this period.
204 *
205 * Returns 0 on success or a negative error code.
206 *
207 */
208int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
209 struct gnet_stats_basic_cpu __percpu *cpu_bstats,
210 struct gnet_stats_rate_est64 *rate_est,
211 spinlock_t *stats_lock,
212 struct nlattr *opt)
213{
214 struct gen_estimator *est;
215 struct gnet_estimator *parm = nla_data(opt);
216 struct gnet_stats_basic_packed b = {0};
217 int idx;
218
219 if (nla_len(opt) < sizeof(*parm))
220 return -EINVAL;
221
222 if (parm->interval < -2 || parm->interval > 3)
223 return -EINVAL;
224
225 est = kzalloc(sizeof(*est), GFP_KERNEL);
226 if (est == NULL)
227 return -ENOBUFS;
228
229 __gnet_stats_copy_basic(&b, cpu_bstats, bstats);
230
231 idx = parm->interval + 2;
232 est->bstats = bstats;
233 est->rate_est = rate_est;
234 est->stats_lock = stats_lock;
235 est->ewma_log = parm->ewma_log;
236 est->last_bytes = b.bytes;
237 est->avbps = rate_est->bps<<5;
238 est->last_packets = b.packets;
239 est->avpps = rate_est->pps<<10;
240 est->cpu_bstats = cpu_bstats;
241
242 spin_lock_bh(&est_tree_lock);
243 if (!elist[idx].timer.function) {
244 INIT_LIST_HEAD(&elist[idx].list);
245 setup_timer(&elist[idx].timer, est_timer, idx);
246 }
247
248 if (list_empty(&elist[idx].list))
249 mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx));
250
251 list_add_rcu(&est->list, &elist[idx].list);
252 gen_add_node(est);
253 spin_unlock_bh(&est_tree_lock);
254
255 return 0;
256}
257EXPORT_SYMBOL(gen_new_estimator);
258
259/**
260 * gen_kill_estimator - remove a rate estimator
261 * @bstats: basic statistics
262 * @rate_est: rate estimator statistics
263 *
264 * Removes the rate estimator specified by &bstats and &rate_est.
265 *
266 * Note : Caller should respect an RCU grace period before freeing stats_lock
267 */
268void gen_kill_estimator(struct gnet_stats_basic_packed *bstats,
269 struct gnet_stats_rate_est64 *rate_est)
270{
271 struct gen_estimator *e;
272
273 spin_lock_bh(&est_tree_lock);
274 while ((e = gen_find_node(bstats, rate_est))) {
275 rb_erase(&e->node, &est_root);
276
277 write_lock(&est_lock);
278 e->bstats = NULL;
279 write_unlock(&est_lock);
280
281 list_del_rcu(&e->list);
282 kfree_rcu(e, e_rcu);
283 }
284 spin_unlock_bh(&est_tree_lock);
285}
286EXPORT_SYMBOL(gen_kill_estimator);
287
288/**
289 * gen_replace_estimator - replace rate estimator configuration
290 * @bstats: basic statistics
291 * @cpu_bstats: bstats per cpu
292 * @rate_est: rate estimator statistics
293 * @stats_lock: statistics lock
294 * @opt: rate estimator configuration TLV
295 *
296 * Replaces the configuration of a rate estimator by calling
297 * gen_kill_estimator() and gen_new_estimator().
298 *
299 * Returns 0 on success or a negative error code.
300 */
301int gen_replace_estimator(struct gnet_stats_basic_packed *bstats,
302 struct gnet_stats_basic_cpu __percpu *cpu_bstats,
303 struct gnet_stats_rate_est64 *rate_est,
304 spinlock_t *stats_lock, struct nlattr *opt)
305{
306 gen_kill_estimator(bstats, rate_est);
307 return gen_new_estimator(bstats, cpu_bstats, rate_est, stats_lock, opt);
308}
309EXPORT_SYMBOL(gen_replace_estimator);
310
311/**
312 * gen_estimator_active - test if estimator is currently in use
313 * @bstats: basic statistics
314 * @rate_est: rate estimator statistics
315 *
316 * Returns true if estimator is active, and false if not.
317 */
318bool gen_estimator_active(const struct gnet_stats_basic_packed *bstats,
319 const struct gnet_stats_rate_est64 *rate_est)
320{
321 bool res;
322
323 ASSERT_RTNL();
324
325 spin_lock_bh(&est_tree_lock);
326 res = gen_find_node(bstats, rate_est) != NULL;
327 spin_unlock_bh(&est_tree_lock);
328
329 return res;
330}
331EXPORT_SYMBOL(gen_estimator_active);