summaryrefslogtreecommitdiff
path: root/net/core/gen_estimator.c
blob: 9fbe7f7429b0efd036cc9e4a7df06293f85a8f0b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
/*
 * net/sched/gen_estimator.c	Simple rate estimator.
 *
 *		This program is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 *
 * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *
 * Changes:
 *              Jamal Hadi Salim - moved it to net/core and reshulfed
 *              names to make it usable in general net subsystem.
 */

#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/bitops.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/in.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/init.h>
#include <linux/rbtree.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <net/gen_stats.h>

/*
   This code is NOT intended to be used for statistics collection,
   its purpose is to provide a base for statistical multiplexing
   for controlled load service.
   If you need only statistics, run a user level daemon which
   periodically reads byte counters.

   Unfortunately, rate estimation is not a very easy task.
   F.e. I did not find a simple way to estimate the current peak rate
   and even failed to formulate the problem 8)8)

   So I preferred not to built an estimator into the scheduler,
   but run this task separately.
   Ideally, it should be kernel thread(s), but for now it runs
   from timers, which puts apparent top bounds on the number of rated
   flows, has minimal overhead on small, but is enough
   to handle controlled load service, sets of aggregates.

   We measure rate over A=(1<<interval) seconds and evaluate EWMA:

   avrate = avrate*(1-W) + rate*W

   where W is chosen as negative power of 2: W = 2^(-ewma_log)

   The resulting time constant is:

   T = A/(-ln(1-W))


   NOTES.

   * avbps is scaled by 2^5, avpps is scaled by 2^10.
   * both values are reported as 32 bit unsigned values. bps can
     overflow for fast links : max speed being 34360Mbit/sec
   * Minimal interval is HZ/4=250msec (it is the greatest common divisor
     for HZ=100 and HZ=1024 8)), maximal interval
     is (HZ*2^EST_MAX_INTERVAL)/4 = 8sec. Shorter intervals
     are too expensive, longer ones can be implemented
     at user level painlessly.
 */

#define EST_MAX_INTERVAL	5

struct gen_estimator
{
	struct list_head	list;
	struct gnet_stats_basic_packed	*bstats;
	struct gnet_stats_rate_est	*rate_est;
	spinlock_t		*stats_lock;
	int			ewma_log;
	u64			last_bytes;
	u64			avbps;
	u32			last_packets;
	u32			avpps;
	struct rcu_head		e_rcu;
	struct rb_node		node;
};

struct gen_estimator_head
{
	struct timer_list	timer;
	struct list_head	list;
};

static struct gen_estimator_head elist[EST_MAX_INTERVAL+1];

/* Protects against NULL dereference */
static DEFINE_RWLOCK(est_lock);

/* Protects against soft lockup during large deletion */
static struct rb_root est_root = RB_ROOT;
static DEFINE_SPINLOCK(est_tree_lock);

static void est_timer(unsigned long arg)
{
	int idx = (int)arg;
	struct gen_estimator *e;

	rcu_read_lock();
	list_for_each_entry_rcu(e, &elist[idx].list, list) {
		u64 nbytes;
		u64 brate;
		u32 npackets;
		u32 rate;

		spin_lock(e->stats_lock);
		read_lock(&est_lock);
		if (e->bstats == NULL)
			goto skip;

		nbytes = e->bstats->bytes;
		npackets = e->bstats->packets;
		brate = (nbytes - e->last_bytes)<<(7 - idx);
		e->last_bytes = nbytes;
		e->avbps += (brate >> e->ewma_log) - (e->avbps >> e->ewma_log);
		e->rate_est->bps = (e->avbps+0xF)>>5;

		rate = (npackets - e->last_packets)<<(12 - idx);
		e->last_packets = npackets;
		e->avpps += (rate >> e->ewma_log) - (e->avpps >> e->ewma_log);
		e->rate_est->pps = (e->avpps+0x1FF)>>10;
skip:
		read_unlock(&est_lock);
		spin_unlock(e->stats_lock);
	}

	if (!list_empty(&elist[idx].list))
		mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx));
	rcu_read_unlock();
}

static void gen_add_node(struct gen_estimator *est)
{
	struct rb_node **p = &est_root.rb_node, *parent = NULL;

	while (*p) {
		struct gen_estimator *e;

		parent = *p;
		e = rb_entry(parent, struct gen_estimator, node);

		if (est->bstats > e->bstats)
			p = &parent->rb_right;
		else
			p = &parent->rb_left;
	}
	rb_link_node(&est->node, parent, p);
	rb_insert_color(&est->node, &est_root);
}

static
struct gen_estimator *gen_find_node(const struct gnet_stats_basic_packed *bstats,
				    const struct gnet_stats_rate_est *rate_est)
{
	struct rb_node *p = est_root.rb_node;

	while (p) {
		struct gen_estimator *e;

		e = rb_entry(p, struct gen_estimator, node);

		if (bstats > e->bstats)
			p = p->rb_right;
		else if (bstats < e->bstats || rate_est != e->rate_est)
			p = p->rb_left;
		else
			return e;
	}
	return NULL;
}

/**
 * gen_new_estimator - create a new rate estimator
 * @bstats: basic statistics
 * @rate_est: rate estimator statistics
 * @stats_lock: statistics lock
 * @opt: rate estimator configuration TLV
 *
 * Creates a new rate estimator with &bstats as source and &rate_est
 * as destination. A new timer with the interval specified in the
 * configuration TLV is created. Upon each interval, the latest statistics
 * will be read from &bstats and the estimated rate will be stored in
 * &rate_est with the statistics lock grabed during this period.
 *
 * Returns 0 on success or a negative error code.
 *
 */
int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
		      struct gnet_stats_rate_est *rate_est,
		      spinlock_t *stats_lock,
		      struct nlattr *opt)
{
	struct gen_estimator *est;
	struct gnet_estimator *parm = nla_data(opt);
	int idx;

	if (nla_len(opt) < sizeof(*parm))
		return -EINVAL;

	if (parm->interval < -2 || parm->interval > 3)
		return -EINVAL;

	est = kzalloc(sizeof(*est), GFP_KERNEL);
	if (est == NULL)
		return -ENOBUFS;

	idx = parm->interval + 2;
	est->bstats = bstats;
	est->rate_est = rate_est;
	est->stats_lock = stats_lock;
	est->ewma_log = parm->ewma_log;
	est->last_bytes = bstats->bytes;
	est->avbps = rate_est->bps<<5;
	est->last_packets = bstats->packets;
	est->avpps = rate_est->pps<<10;

	spin_lock(&est_tree_lock);
	if (!elist[idx].timer.function) {
		INIT_LIST_HEAD(&elist[idx].list);
		setup_timer(&elist[idx].timer, est_timer, idx);
	}

	if (list_empty(&elist[idx].list))
		mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx));

	list_add_rcu(&est->list, &elist[idx].list);
	gen_add_node(est);
	spin_unlock(&est_tree_lock);

	return 0;
}
EXPORT_SYMBOL(gen_new_estimator);

static void __gen_kill_estimator(struct rcu_head *head)
{
	struct gen_estimator *e = container_of(head,
					struct gen_estimator, e_rcu);
	kfree(e);
}

/**
 * gen_kill_estimator - remove a rate estimator
 * @bstats: basic statistics
 * @rate_est: rate estimator statistics
 *
 * Removes the rate estimator specified by &bstats and &rate_est.
 *
 * Note : Caller should respect an RCU grace period before freeing stats_lock
 */
void gen_kill_estimator(struct gnet_stats_basic_packed *bstats,
			struct gnet_stats_rate_est *rate_est)
{
	struct gen_estimator *e;

	spin_lock(&est_tree_lock);
	while ((e = gen_find_node(bstats, rate_est))) {
		rb_erase(&e->node, &est_root);

		write_lock_bh(&est_lock);
		e->bstats = NULL;
		write_unlock_bh(&est_lock);

		list_del_rcu(&e->list);
		call_rcu(&e->e_rcu, __gen_kill_estimator);
	}
	spin_unlock(&est_tree_lock);
}
EXPORT_SYMBOL(gen_kill_estimator);

/**
 * gen_replace_estimator - replace rate estimator configuration
 * @bstats: basic statistics
 * @rate_est: rate estimator statistics
 * @stats_lock: statistics lock
 * @opt: rate estimator configuration TLV
 *
 * Replaces the configuration of a rate estimator by calling
 * gen_kill_estimator() and gen_new_estimator().
 *
 * Returns 0 on success or a negative error code.
 */
int gen_replace_estimator(struct gnet_stats_basic_packed *bstats,
			  struct gnet_stats_rate_est *rate_est,
			  spinlock_t *stats_lock, struct nlattr *opt)
{
	gen_kill_estimator(bstats, rate_est);
	return gen_new_estimator(bstats, rate_est, stats_lock, opt);
}
EXPORT_SYMBOL(gen_replace_estimator);

/**
 * gen_estimator_active - test if estimator is currently in use
 * @bstats: basic statistics
 * @rate_est: rate estimator statistics
 *
 * Returns true if estimator is active, and false if not.
 */
bool gen_estimator_active(const struct gnet_stats_basic_packed *bstats,
			  const struct gnet_stats_rate_est *rate_est)
{
	bool res;

	ASSERT_RTNL();

	spin_lock(&est_tree_lock);
	res = gen_find_node(bstats, rate_est) != NULL;
	spin_unlock(&est_tree_lock);

	return res;
}
EXPORT_SYMBOL(gen_estimator_active);