aboutsummaryrefslogtreecommitdiffstats
path: root/net/sched/estimator.c
blob: 5d3ae03e22a70fdf49350f833a282c0a3e12624a (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
/*
 * net/sched/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>
 */

#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 <net/sock.h>
#include <net/pkt_sched.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.

   * The stored value for avbps is scaled by 2^5, so that maximal
     rate is ~1Gbit, avpps is scaled by 2^10.

   * 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 qdisc_estimator
{
	struct qdisc_estimator	*next;
	struct tc_stats		*stats;
	spinlock_t		*stats_lock;
	unsigned		interval;
	int			ewma_log;
	u64			last_bytes;
	u32			last_packets;
	u32			avpps;
	u32			avbps;
};

struct qdisc_estimator_head
{
	struct timer_list	timer;
	struct qdisc_estimator	*list;
};

static struct qdisc_estimator_head elist[EST_MAX_INTERVAL+1];

/* Estimator array lock */
static DEFINE_RWLOCK(est_lock);

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

	read_lock(&est_lock);
	for (e = elist[idx].list; e; e = e->next) {
		struct tc_stats *st = e->stats;
		u64 nbytes;
		u32 npackets;
		u32 rate;

		spin_lock(e->stats_lock);
		nbytes = st->bytes;
		npackets = st->packets;
		rate = (nbytes - e->last_bytes)<<(7 - idx);
		e->last_bytes = nbytes;
		e->avbps += ((long)rate - (long)e->avbps) >> e->ewma_log;
		st->bps = (e->avbps+0xF)>>5;

		rate = (npackets - e->last_packets)<<(12 - idx);
		e->last_packets = npackets;
		e->avpps += ((long)rate - (long)e->avpps) >> e->ewma_log;
		e->stats->pps = (e->avpps+0x1FF)>>10;
		spin_unlock(e->stats_lock);
	}

	mod_timer(&elist[idx].timer, jiffies + ((HZ<<idx)/4));
	read_unlock(&est_lock);
}

int qdisc_new_estimator(struct tc_stats *stats, spinlock_t *stats_lock, struct rtattr *opt)
{
	struct qdisc_estimator *est;
	struct tc_estimator *parm = RTA_DATA(opt);

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

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

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

	memset(est, 0, sizeof(*est));
	est->interval = parm->interval + 2;
	est->stats = stats;
	est->stats_lock = stats_lock;
	est->ewma_log = parm->ewma_log;
	est->last_bytes = stats->bytes;
	est->avbps = stats->bps<<5;
	est->last_packets = stats->packets;
	est->avpps = stats->pps<<10;

	est->next = elist[est->interval].list;
	if (est->next == NULL) {
		init_timer(&elist[est->interval].timer);
		elist[est->interval].timer.data = est->interval;
		elist[est->interval].timer.expires = jiffies + ((HZ<<est->interval)/4);
		elist[est->interval].timer.function = est_timer;
		add_timer(&elist[est->interval].timer);
	}
	write_lock_bh(&est_lock);
	elist[est->interval].list = est;
	write_unlock_bh(&est_lock);
	return 0;
}

void qdisc_kill_estimator(struct tc_stats *stats)
{
	int idx;
	struct qdisc_estimator *est, **pest;

	for (idx=0; idx <= EST_MAX_INTERVAL; idx++) {
		int killed = 0;
		pest = &elist[idx].list;
		while ((est=*pest) != NULL) {
			if (est->stats != stats) {
				pest = &est->next;
				continue;
			}

			write_lock_bh(&est_lock);
			*pest = est->next;
			write_unlock_bh(&est_lock);

			kfree(est);
			killed++;
		}
		if (killed && elist[idx].list == NULL)
			del_timer(&elist[idx].timer);
	}
}

EXPORT_SYMBOL(qdisc_kill_estimator);
EXPORT_SYMBOL(qdisc_new_estimator);