2 * net/sched/estimator.c Simple rate estimator.
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.
9 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
12 #include <asm/uaccess.h>
13 #include <asm/system.h>
14 #include <asm/bitops.h>
15 #include <linux/types.h>
16 #include <linux/kernel.h>
17 #include <linux/sched.h>
18 #include <linux/string.h>
20 #include <linux/socket.h>
21 #include <linux/sockios.h>
23 #include <linux/errno.h>
24 #include <linux/interrupt.h>
25 #include <linux/netdevice.h>
26 #include <linux/skbuff.h>
27 #include <linux/rtnetlink.h>
28 #include <linux/init.h>
29 #include <linux/proc_fs.h>
31 #include <net/pkt_sched.h>
34 This code is NOT intended to be used for statistics collection,
35 its purpose is to provide a base for statistical multiplexing
36 for controlled load service.
37 If you need only statistics, run a user level daemon which
38 periodically reads byte counters.
40 Unfortunately, rate estimation is not a very easy task.
41 F.e. I did not find a simple way to estimate the current peak rate
42 and even failed to formulate the problem 8)8)
44 So I preferred not to built an estimator into the scheduler,
45 but run this task separately.
46 Ideally, it should be kernel thread(s), but for now it runs
47 from timers, which puts apparent top bounds on the number of rated
48 flows, has minimal overhead on small, but is enough
49 to handle controlled load service, sets of aggregates.
51 We measure rate over A=(1<<interval) seconds and evaluate EWMA:
53 avrate = avrate*(1-W) + rate*W
55 where W is chosen as negative power of 2: W = 2^(-ewma_log)
57 The resulting time constant is:
64 * The stored value for avbps is scaled by 2^5, so that maximal
65 rate is ~1Gbit, avpps is scaled by 2^10.
67 * Minimal interval is HZ/4=250msec (it is the greatest common divisor
68 for HZ=100 and HZ=1024 8)), maximal interval
69 is (HZ*2^EST_MAX_INTERVAL)/4 = 8sec. Shorter intervals
70 are too expensive, longer ones can be implemented
71 at user level painlessly.
74 #define EST_MAX_INTERVAL 5
76 struct qdisc_estimator
78 struct qdisc_estimator *next;
79 struct tc_stats *stats;
88 struct qdisc_estimator_head
90 struct timer_list timer;
91 struct qdisc_estimator *list;
94 static struct qdisc_estimator_head elist[EST_MAX_INTERVAL+1];
96 /* Estimator array lock */
97 static rwlock_t est_lock = RW_LOCK_UNLOCKED;
99 static void est_timer(unsigned long arg)
102 struct qdisc_estimator *e;
104 read_lock(&est_lock);
105 for (e = elist[idx].list; e; e = e->next) {
106 struct tc_stats *st = e->stats;
113 npackets = st->packets;
114 rate = (nbytes - e->last_bytes)<<(7 - idx);
115 e->last_bytes = nbytes;
116 e->avbps += ((long)rate - (long)e->avbps) >> e->ewma_log;
117 st->bps = (e->avbps+0xF)>>5;
119 rate = (npackets - e->last_packets)<<(12 - idx);
120 e->last_packets = npackets;
121 e->avpps += ((long)rate - (long)e->avpps) >> e->ewma_log;
122 e->stats->pps = (e->avpps+0x1FF)>>10;
123 spin_unlock(st->lock);
126 mod_timer(&elist[idx].timer, jiffies + ((HZ<<idx)/4));
127 read_unlock(&est_lock);
130 int qdisc_new_estimator(struct tc_stats *stats, struct rtattr *opt)
132 struct qdisc_estimator *est;
133 struct tc_estimator *parm = RTA_DATA(opt);
135 if (RTA_PAYLOAD(opt) < sizeof(*parm))
138 if (parm->interval < -2 || parm->interval > 3)
141 est = kmalloc(sizeof(*est), GFP_KERNEL);
145 memset(est, 0, sizeof(*est));
146 est->interval = parm->interval + 2;
148 est->ewma_log = parm->ewma_log;
149 est->last_bytes = stats->bytes;
150 est->avbps = stats->bps<<5;
151 est->last_packets = stats->packets;
152 est->avpps = stats->pps<<10;
154 est->next = elist[est->interval].list;
155 if (est->next == NULL) {
156 init_timer(&elist[est->interval].timer);
157 elist[est->interval].timer.data = est->interval;
158 elist[est->interval].timer.expires = jiffies + ((HZ<<est->interval)/4);
159 elist[est->interval].timer.function = est_timer;
160 add_timer(&elist[est->interval].timer);
162 write_lock_bh(&est_lock);
163 elist[est->interval].list = est;
164 write_unlock_bh(&est_lock);
168 void qdisc_kill_estimator(struct tc_stats *stats)
171 struct qdisc_estimator *est, **pest;
173 for (idx=0; idx <= EST_MAX_INTERVAL; idx++) {
175 pest = &elist[idx].list;
176 while ((est=*pest) != NULL) {
177 if (est->stats != stats) {
182 write_lock_bh(&est_lock);
184 write_unlock_bh(&est_lock);
189 if (killed && elist[idx].list == NULL)
190 del_timer(&elist[idx].timer);