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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_packed *bstats;
44 spinlock_t *stats_lock;
45 seqcount_t *running;
46 struct gnet_stats_basic_cpu __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_packed *b)
64{
65 memset(b, 0, sizeof(*b));
66 if (e->stats_lock)
67 spin_lock(e->stats_lock);
68
69 __gnet_stats_copy_basic(e->running, b, e->cpu_bstats, e->bstats);
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_packed b;
80 u64 rate, brate;
81
82 est_fetch_counters(est, &b);
83 brate = (b.bytes - est->last_bytes) << (10 - est->intvl_log);
84 brate = (brate >> est->ewma_log) - (est->avbps >> est->ewma_log);
85
86 rate = (b.packets - est->last_packets) << (10 - est->intvl_log);
87 rate = (rate >> est->ewma_log) - (est->avpps >> est->ewma_log);
88
89 write_seqcount_begin(&est->seq);
90 est->avbps += brate;
91 est->avpps += rate;
92 write_seqcount_end(&est->seq);
93
94 est->last_bytes = b.bytes;
95 est->last_packets = b.packets;
96
97 est->next_jiffies += ((HZ/4) << est->intvl_log);
98
99 if (unlikely(time_after_eq(jiffies, est->next_jiffies))) {
100 /* Ouch... timer was delayed. */
101 est->next_jiffies = jiffies + 1;
102 }
103 mod_timer(&est->timer, est->next_jiffies);
104}
105
106/**
107 * gen_new_estimator - create a new rate estimator
108 * @bstats: basic statistics
109 * @cpu_bstats: bstats per cpu
110 * @rate_est: rate estimator statistics
111 * @lock: lock for statistics and control path
112 * @running: qdisc running seqcount
113 * @opt: rate estimator configuration TLV
114 *
115 * Creates a new rate estimator with &bstats as source and &rate_est
116 * as destination. A new timer with the interval specified in the
117 * configuration TLV is created. Upon each interval, the latest statistics
118 * will be read from &bstats and the estimated rate will be stored in
119 * &rate_est with the statistics lock grabbed during this period.
120 *
121 * Returns 0 on success or a negative error code.
122 *
123 */
124int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
125 struct gnet_stats_basic_cpu __percpu *cpu_bstats,
126 struct net_rate_estimator __rcu **rate_est,
127 spinlock_t *lock,
128 seqcount_t *running,
129 struct nlattr *opt)
130{
131 struct gnet_estimator *parm = nla_data(opt);
132 struct net_rate_estimator *old, *est;
133 struct gnet_stats_basic_packed b;
134 int intvl_log;
135
136 if (nla_len(opt) < sizeof(*parm))
137 return -EINVAL;
138
139 /* allowed timer periods are :
140 * -2 : 250ms, -1 : 500ms, 0 : 1 sec
141 * 1 : 2 sec, 2 : 4 sec, 3 : 8 sec
142 */
143 if (parm->interval < -2 || parm->interval > 3)
144 return -EINVAL;
145
146 if (parm->ewma_log == 0 || parm->ewma_log >= 31)
147 return -EINVAL;
148
149 est = kzalloc(sizeof(*est), GFP_KERNEL);
150 if (!est)
151 return -ENOBUFS;
152
153 seqcount_init(&est->seq);
154 intvl_log = parm->interval + 2;
155 est->bstats = bstats;
156 est->stats_lock = lock;
157 est->running = running;
158 est->ewma_log = parm->ewma_log;
159 est->intvl_log = intvl_log;
160 est->cpu_bstats = cpu_bstats;
161
162 if (lock)
163 local_bh_disable();
164 est_fetch_counters(est, &b);
165 if (lock)
166 local_bh_enable();
167 est->last_bytes = b.bytes;
168 est->last_packets = b.packets;
169
170 if (lock)
171 spin_lock_bh(lock);
172 old = rcu_dereference_protected(*rate_est, 1);
173 if (old) {
174 del_timer_sync(&old->timer);
175 est->avbps = old->avbps;
176 est->avpps = old->avpps;
177 }
178
179 est->next_jiffies = jiffies + ((HZ/4) << intvl_log);
180 timer_setup(&est->timer, est_timer, 0);
181 mod_timer(&est->timer, est->next_jiffies);
182
183 rcu_assign_pointer(*rate_est, est);
184 if (lock)
185 spin_unlock_bh(lock);
186 if (old)
187 kfree_rcu(old, rcu);
188 return 0;
189}
190EXPORT_SYMBOL(gen_new_estimator);
191
192/**
193 * gen_kill_estimator - remove a rate estimator
194 * @rate_est: rate estimator
195 *
196 * Removes the rate estimator.
197 *
198 */
199void gen_kill_estimator(struct net_rate_estimator __rcu **rate_est)
200{
201 struct net_rate_estimator *est;
202
203 est = xchg((__force struct net_rate_estimator **)rate_est, NULL);
204 if (est) {
205 del_timer_sync(&est->timer);
206 kfree_rcu(est, rcu);
207 }
208}
209EXPORT_SYMBOL(gen_kill_estimator);
210
211/**
212 * gen_replace_estimator - replace rate estimator configuration
213 * @bstats: basic statistics
214 * @cpu_bstats: bstats per cpu
215 * @rate_est: rate estimator statistics
216 * @lock: lock for statistics and control path
217 * @running: qdisc running seqcount (might be NULL)
218 * @opt: rate estimator configuration TLV
219 *
220 * Replaces the configuration of a rate estimator by calling
221 * gen_kill_estimator() and gen_new_estimator().
222 *
223 * Returns 0 on success or a negative error code.
224 */
225int gen_replace_estimator(struct gnet_stats_basic_packed *bstats,
226 struct gnet_stats_basic_cpu __percpu *cpu_bstats,
227 struct net_rate_estimator __rcu **rate_est,
228 spinlock_t *lock,
229 seqcount_t *running, struct nlattr *opt)
230{
231 return gen_new_estimator(bstats, cpu_bstats, rate_est,
232 lock, running, opt);
233}
234EXPORT_SYMBOL(gen_replace_estimator);
235
236/**
237 * gen_estimator_active - test if estimator is currently in use
238 * @rate_est: rate estimator
239 *
240 * Returns true if estimator is active, and false if not.
241 */
242bool gen_estimator_active(struct net_rate_estimator __rcu **rate_est)
243{
244 return !!rcu_access_pointer(*rate_est);
245}
246EXPORT_SYMBOL(gen_estimator_active);
247
248bool gen_estimator_read(struct net_rate_estimator __rcu **rate_est,
249 struct gnet_stats_rate_est64 *sample)
250{
251 struct net_rate_estimator *est;
252 unsigned seq;
253
254 rcu_read_lock();
255 est = rcu_dereference(*rate_est);
256 if (!est) {
257 rcu_read_unlock();
258 return false;
259 }
260
261 do {
262 seq = read_seqcount_begin(&est->seq);
263 sample->bps = est->avbps >> 8;
264 sample->pps = est->avpps >> 8;
265 } while (read_seqcount_retry(&est->seq, seq));
266
267 rcu_read_unlock();
268 return true;
269}
270EXPORT_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 is scaled by 2^5, avpps is scaled by 2^10.
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_est *rate_est;
86 spinlock_t *stats_lock;
87 int ewma_log;
88 u64 last_bytes;
89 u64 avbps;
90 u32 last_packets;
91 u32 avpps;
92 struct rcu_head e_rcu;
93 struct rb_node node;
94};
95
96struct gen_estimator_head
97{
98 struct timer_list timer;
99 struct list_head list;
100};
101
102static struct gen_estimator_head elist[EST_MAX_INTERVAL+1];
103
104/* Protects against NULL dereference */
105static DEFINE_RWLOCK(est_lock);
106
107/* Protects against soft lockup during large deletion */
108static struct rb_root est_root = RB_ROOT;
109static DEFINE_SPINLOCK(est_tree_lock);
110
111static void est_timer(unsigned long arg)
112{
113 int idx = (int)arg;
114 struct gen_estimator *e;
115
116 rcu_read_lock();
117 list_for_each_entry_rcu(e, &elist[idx].list, list) {
118 u64 nbytes;
119 u64 brate;
120 u32 npackets;
121 u32 rate;
122
123 spin_lock(e->stats_lock);
124 read_lock(&est_lock);
125 if (e->bstats == NULL)
126 goto skip;
127
128 nbytes = e->bstats->bytes;
129 npackets = e->bstats->packets;
130 brate = (nbytes - e->last_bytes)<<(7 - idx);
131 e->last_bytes = nbytes;
132 e->avbps += (brate >> e->ewma_log) - (e->avbps >> e->ewma_log);
133 e->rate_est->bps = (e->avbps+0xF)>>5;
134
135 rate = (npackets - e->last_packets)<<(12 - idx);
136 e->last_packets = npackets;
137 e->avpps += (rate >> e->ewma_log) - (e->avpps >> e->ewma_log);
138 e->rate_est->pps = (e->avpps+0x1FF)>>10;
139skip:
140 read_unlock(&est_lock);
141 spin_unlock(e->stats_lock);
142 }
143
144 if (!list_empty(&elist[idx].list))
145 mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx));
146 rcu_read_unlock();
147}
148
149static void gen_add_node(struct gen_estimator *est)
150{
151 struct rb_node **p = &est_root.rb_node, *parent = NULL;
152
153 while (*p) {
154 struct gen_estimator *e;
155
156 parent = *p;
157 e = rb_entry(parent, struct gen_estimator, node);
158
159 if (est->bstats > e->bstats)
160 p = &parent->rb_right;
161 else
162 p = &parent->rb_left;
163 }
164 rb_link_node(&est->node, parent, p);
165 rb_insert_color(&est->node, &est_root);
166}
167
168static
169struct gen_estimator *gen_find_node(const struct gnet_stats_basic_packed *bstats,
170 const struct gnet_stats_rate_est *rate_est)
171{
172 struct rb_node *p = est_root.rb_node;
173
174 while (p) {
175 struct gen_estimator *e;
176
177 e = rb_entry(p, struct gen_estimator, node);
178
179 if (bstats > e->bstats)
180 p = p->rb_right;
181 else if (bstats < e->bstats || rate_est != e->rate_est)
182 p = p->rb_left;
183 else
184 return e;
185 }
186 return NULL;
187}
188
189/**
190 * gen_new_estimator - create a new rate estimator
191 * @bstats: basic statistics
192 * @rate_est: rate estimator statistics
193 * @stats_lock: statistics lock
194 * @opt: rate estimator configuration TLV
195 *
196 * Creates a new rate estimator with &bstats as source and &rate_est
197 * as destination. A new timer with the interval specified in the
198 * configuration TLV is created. Upon each interval, the latest statistics
199 * will be read from &bstats and the estimated rate will be stored in
200 * &rate_est with the statistics lock grabed during this period.
201 *
202 * Returns 0 on success or a negative error code.
203 *
204 */
205int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
206 struct gnet_stats_rate_est *rate_est,
207 spinlock_t *stats_lock,
208 struct nlattr *opt)
209{
210 struct gen_estimator *est;
211 struct gnet_estimator *parm = nla_data(opt);
212 int idx;
213
214 if (nla_len(opt) < sizeof(*parm))
215 return -EINVAL;
216
217 if (parm->interval < -2 || parm->interval > 3)
218 return -EINVAL;
219
220 est = kzalloc(sizeof(*est), GFP_KERNEL);
221 if (est == NULL)
222 return -ENOBUFS;
223
224 idx = parm->interval + 2;
225 est->bstats = bstats;
226 est->rate_est = rate_est;
227 est->stats_lock = stats_lock;
228 est->ewma_log = parm->ewma_log;
229 est->last_bytes = bstats->bytes;
230 est->avbps = rate_est->bps<<5;
231 est->last_packets = bstats->packets;
232 est->avpps = rate_est->pps<<10;
233
234 spin_lock_bh(&est_tree_lock);
235 if (!elist[idx].timer.function) {
236 INIT_LIST_HEAD(&elist[idx].list);
237 setup_timer(&elist[idx].timer, est_timer, idx);
238 }
239
240 if (list_empty(&elist[idx].list))
241 mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx));
242
243 list_add_rcu(&est->list, &elist[idx].list);
244 gen_add_node(est);
245 spin_unlock_bh(&est_tree_lock);
246
247 return 0;
248}
249EXPORT_SYMBOL(gen_new_estimator);
250
251/**
252 * gen_kill_estimator - remove a rate estimator
253 * @bstats: basic statistics
254 * @rate_est: rate estimator statistics
255 *
256 * Removes the rate estimator specified by &bstats and &rate_est.
257 *
258 * Note : Caller should respect an RCU grace period before freeing stats_lock
259 */
260void gen_kill_estimator(struct gnet_stats_basic_packed *bstats,
261 struct gnet_stats_rate_est *rate_est)
262{
263 struct gen_estimator *e;
264
265 spin_lock_bh(&est_tree_lock);
266 while ((e = gen_find_node(bstats, rate_est))) {
267 rb_erase(&e->node, &est_root);
268
269 write_lock(&est_lock);
270 e->bstats = NULL;
271 write_unlock(&est_lock);
272
273 list_del_rcu(&e->list);
274 kfree_rcu(e, e_rcu);
275 }
276 spin_unlock_bh(&est_tree_lock);
277}
278EXPORT_SYMBOL(gen_kill_estimator);
279
280/**
281 * gen_replace_estimator - replace rate estimator configuration
282 * @bstats: basic statistics
283 * @rate_est: rate estimator statistics
284 * @stats_lock: statistics lock
285 * @opt: rate estimator configuration TLV
286 *
287 * Replaces the configuration of a rate estimator by calling
288 * gen_kill_estimator() and gen_new_estimator().
289 *
290 * Returns 0 on success or a negative error code.
291 */
292int gen_replace_estimator(struct gnet_stats_basic_packed *bstats,
293 struct gnet_stats_rate_est *rate_est,
294 spinlock_t *stats_lock, struct nlattr *opt)
295{
296 gen_kill_estimator(bstats, rate_est);
297 return gen_new_estimator(bstats, rate_est, stats_lock, opt);
298}
299EXPORT_SYMBOL(gen_replace_estimator);
300
301/**
302 * gen_estimator_active - test if estimator is currently in use
303 * @bstats: basic statistics
304 * @rate_est: rate estimator statistics
305 *
306 * Returns true if estimator is active, and false if not.
307 */
308bool gen_estimator_active(const struct gnet_stats_basic_packed *bstats,
309 const struct gnet_stats_rate_est *rate_est)
310{
311 bool res;
312
313 ASSERT_RTNL();
314
315 spin_lock_bh(&est_tree_lock);
316 res = gen_find_node(bstats, rate_est) != NULL;
317 spin_unlock_bh(&est_tree_lock);
318
319 return res;
320}
321EXPORT_SYMBOL(gen_estimator_active);