Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 <asm/system.h> |
| 18 | #include <asm/bitops.h> |
| 19 | #include <linux/module.h> |
| 20 | #include <linux/types.h> |
| 21 | #include <linux/kernel.h> |
| 22 | #include <linux/jiffies.h> |
| 23 | #include <linux/string.h> |
| 24 | #include <linux/mm.h> |
| 25 | #include <linux/socket.h> |
| 26 | #include <linux/sockios.h> |
| 27 | #include <linux/in.h> |
| 28 | #include <linux/errno.h> |
| 29 | #include <linux/interrupt.h> |
| 30 | #include <linux/netdevice.h> |
| 31 | #include <linux/skbuff.h> |
| 32 | #include <linux/rtnetlink.h> |
| 33 | #include <linux/init.h> |
| 34 | #include <net/sock.h> |
| 35 | #include <net/gen_stats.h> |
| 36 | |
| 37 | /* |
| 38 | This code is NOT intended to be used for statistics collection, |
| 39 | its purpose is to provide a base for statistical multiplexing |
| 40 | for controlled load service. |
| 41 | If you need only statistics, run a user level daemon which |
| 42 | periodically reads byte counters. |
| 43 | |
| 44 | Unfortunately, rate estimation is not a very easy task. |
| 45 | F.e. I did not find a simple way to estimate the current peak rate |
| 46 | and even failed to formulate the problem 8)8) |
| 47 | |
| 48 | So I preferred not to built an estimator into the scheduler, |
| 49 | but run this task separately. |
| 50 | Ideally, it should be kernel thread(s), but for now it runs |
| 51 | from timers, which puts apparent top bounds on the number of rated |
| 52 | flows, has minimal overhead on small, but is enough |
| 53 | to handle controlled load service, sets of aggregates. |
| 54 | |
| 55 | We measure rate over A=(1<<interval) seconds and evaluate EWMA: |
| 56 | |
| 57 | avrate = avrate*(1-W) + rate*W |
| 58 | |
| 59 | where W is chosen as negative power of 2: W = 2^(-ewma_log) |
| 60 | |
| 61 | The resulting time constant is: |
| 62 | |
| 63 | T = A/(-ln(1-W)) |
| 64 | |
| 65 | |
| 66 | NOTES. |
| 67 | |
| 68 | * The stored value for avbps is scaled by 2^5, so that maximal |
| 69 | rate is ~1Gbit, avpps is scaled by 2^10. |
| 70 | |
| 71 | * Minimal interval is HZ/4=250msec (it is the greatest common divisor |
| 72 | for HZ=100 and HZ=1024 8)), maximal interval |
| 73 | is (HZ*2^EST_MAX_INTERVAL)/4 = 8sec. Shorter intervals |
| 74 | are too expensive, longer ones can be implemented |
| 75 | at user level painlessly. |
| 76 | */ |
| 77 | |
| 78 | #define EST_MAX_INTERVAL 5 |
| 79 | |
| 80 | struct gen_estimator |
| 81 | { |
| 82 | struct gen_estimator *next; |
| 83 | struct gnet_stats_basic *bstats; |
| 84 | struct gnet_stats_rate_est *rate_est; |
| 85 | spinlock_t *stats_lock; |
| 86 | unsigned interval; |
| 87 | int ewma_log; |
| 88 | u64 last_bytes; |
| 89 | u32 last_packets; |
| 90 | u32 avpps; |
| 91 | u32 avbps; |
| 92 | }; |
| 93 | |
| 94 | struct gen_estimator_head |
| 95 | { |
| 96 | struct timer_list timer; |
| 97 | struct gen_estimator *list; |
| 98 | }; |
| 99 | |
| 100 | static struct gen_estimator_head elist[EST_MAX_INTERVAL+1]; |
| 101 | |
| 102 | /* Estimator array lock */ |
| 103 | static DEFINE_RWLOCK(est_lock); |
| 104 | |
| 105 | static void est_timer(unsigned long arg) |
| 106 | { |
| 107 | int idx = (int)arg; |
| 108 | struct gen_estimator *e; |
| 109 | |
| 110 | read_lock(&est_lock); |
| 111 | for (e = elist[idx].list; e; e = e->next) { |
| 112 | u64 nbytes; |
| 113 | u32 npackets; |
| 114 | u32 rate; |
| 115 | |
| 116 | spin_lock(e->stats_lock); |
| 117 | nbytes = e->bstats->bytes; |
| 118 | npackets = e->bstats->packets; |
| 119 | rate = (nbytes - e->last_bytes)<<(7 - idx); |
| 120 | e->last_bytes = nbytes; |
| 121 | e->avbps += ((long)rate - (long)e->avbps) >> e->ewma_log; |
| 122 | e->rate_est->bps = (e->avbps+0xF)>>5; |
| 123 | |
| 124 | rate = (npackets - e->last_packets)<<(12 - idx); |
| 125 | e->last_packets = npackets; |
| 126 | e->avpps += ((long)rate - (long)e->avpps) >> e->ewma_log; |
| 127 | e->rate_est->pps = (e->avpps+0x1FF)>>10; |
| 128 | spin_unlock(e->stats_lock); |
| 129 | } |
| 130 | |
| 131 | mod_timer(&elist[idx].timer, jiffies + ((HZ<<idx)/4)); |
| 132 | read_unlock(&est_lock); |
| 133 | } |
| 134 | |
| 135 | /** |
| 136 | * gen_new_estimator - create a new rate estimator |
| 137 | * @bstats: basic statistics |
| 138 | * @rate_est: rate estimator statistics |
| 139 | * @stats_lock: statistics lock |
| 140 | * @opt: rate estimator configuration TLV |
| 141 | * |
| 142 | * Creates a new rate estimator with &bstats as source and &rate_est |
| 143 | * as destination. A new timer with the interval specified in the |
| 144 | * configuration TLV is created. Upon each interval, the latest statistics |
| 145 | * will be read from &bstats and the estimated rate will be stored in |
| 146 | * &rate_est with the statistics lock grabed during this period. |
| 147 | * |
| 148 | * Returns 0 on success or a negative error code. |
| 149 | */ |
| 150 | int gen_new_estimator(struct gnet_stats_basic *bstats, |
| 151 | struct gnet_stats_rate_est *rate_est, spinlock_t *stats_lock, struct rtattr *opt) |
| 152 | { |
| 153 | struct gen_estimator *est; |
| 154 | struct gnet_estimator *parm = RTA_DATA(opt); |
| 155 | |
| 156 | if (RTA_PAYLOAD(opt) < sizeof(*parm)) |
| 157 | return -EINVAL; |
| 158 | |
| 159 | if (parm->interval < -2 || parm->interval > 3) |
| 160 | return -EINVAL; |
| 161 | |
| 162 | est = kmalloc(sizeof(*est), GFP_KERNEL); |
| 163 | if (est == NULL) |
| 164 | return -ENOBUFS; |
| 165 | |
| 166 | memset(est, 0, sizeof(*est)); |
| 167 | est->interval = parm->interval + 2; |
| 168 | est->bstats = bstats; |
| 169 | est->rate_est = rate_est; |
| 170 | est->stats_lock = stats_lock; |
| 171 | est->ewma_log = parm->ewma_log; |
| 172 | est->last_bytes = bstats->bytes; |
| 173 | est->avbps = rate_est->bps<<5; |
| 174 | est->last_packets = bstats->packets; |
| 175 | est->avpps = rate_est->pps<<10; |
| 176 | |
| 177 | est->next = elist[est->interval].list; |
| 178 | if (est->next == NULL) { |
| 179 | init_timer(&elist[est->interval].timer); |
| 180 | elist[est->interval].timer.data = est->interval; |
| 181 | elist[est->interval].timer.expires = jiffies + ((HZ<<est->interval)/4); |
| 182 | elist[est->interval].timer.function = est_timer; |
| 183 | add_timer(&elist[est->interval].timer); |
| 184 | } |
| 185 | write_lock_bh(&est_lock); |
| 186 | elist[est->interval].list = est; |
| 187 | write_unlock_bh(&est_lock); |
| 188 | return 0; |
| 189 | } |
| 190 | |
| 191 | /** |
| 192 | * gen_kill_estimator - remove a rate estimator |
| 193 | * @bstats: basic statistics |
| 194 | * @rate_est: rate estimator statistics |
| 195 | * |
| 196 | * Removes the rate estimator specified by &bstats and &rate_est |
| 197 | * and deletes the timer. |
| 198 | */ |
| 199 | void gen_kill_estimator(struct gnet_stats_basic *bstats, |
| 200 | struct gnet_stats_rate_est *rate_est) |
| 201 | { |
| 202 | int idx; |
| 203 | struct gen_estimator *est, **pest; |
| 204 | |
| 205 | for (idx=0; idx <= EST_MAX_INTERVAL; idx++) { |
| 206 | int killed = 0; |
| 207 | pest = &elist[idx].list; |
| 208 | while ((est=*pest) != NULL) { |
| 209 | if (est->rate_est != rate_est || est->bstats != bstats) { |
| 210 | pest = &est->next; |
| 211 | continue; |
| 212 | } |
| 213 | |
| 214 | write_lock_bh(&est_lock); |
| 215 | *pest = est->next; |
| 216 | write_unlock_bh(&est_lock); |
| 217 | |
| 218 | kfree(est); |
| 219 | killed++; |
| 220 | } |
| 221 | if (killed && elist[idx].list == NULL) |
| 222 | del_timer(&elist[idx].timer); |
| 223 | } |
| 224 | } |
| 225 | |
| 226 | /** |
| 227 | * gen_replace_estimator - replace rate estimator configruation |
| 228 | * @bstats: basic statistics |
| 229 | * @rate_est: rate estimator statistics |
| 230 | * @stats_lock: statistics lock |
| 231 | * @opt: rate estimator configuration TLV |
| 232 | * |
| 233 | * Replaces the configuration of a rate estimator by calling |
| 234 | * gen_kill_estimator() and gen_new_estimator(). |
| 235 | * |
| 236 | * Returns 0 on success or a negative error code. |
| 237 | */ |
| 238 | int |
| 239 | gen_replace_estimator(struct gnet_stats_basic *bstats, |
| 240 | struct gnet_stats_rate_est *rate_est, spinlock_t *stats_lock, |
| 241 | struct rtattr *opt) |
| 242 | { |
| 243 | gen_kill_estimator(bstats, rate_est); |
| 244 | return gen_new_estimator(bstats, rate_est, stats_lock, opt); |
| 245 | } |
| 246 | |
| 247 | |
| 248 | EXPORT_SYMBOL(gen_kill_estimator); |
| 249 | EXPORT_SYMBOL(gen_new_estimator); |
| 250 | EXPORT_SYMBOL(gen_replace_estimator); |