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 and avpps are scaled by 2^5. 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 81 struct gen_estimator 82 { 83 struct list_head list; 84 struct gnet_stats_basic_packed *bstats; 85 struct gnet_stats_rate_est64 *rate_est; 86 spinlock_t *stats_lock; 87 int ewma_log; 88 u32 last_packets; 89 unsigned long avpps; 90 u64 last_bytes; 91 u64 avbps; 92 struct rcu_head e_rcu; 93 struct rb_node node; 94 struct gnet_stats_basic_cpu __percpu *cpu_bstats; 95 struct rcu_head head; 96 }; 97 98 struct gen_estimator_head 99 { 100 struct timer_list timer; 101 struct list_head list; 102 }; 103 104 static struct gen_estimator_head elist[EST_MAX_INTERVAL+1]; 105 106 /* Protects against NULL dereference */ 107 static DEFINE_RWLOCK(est_lock); 108 109 /* Protects against soft lockup during large deletion */ 110 static struct rb_root est_root = RB_ROOT; 111 static DEFINE_SPINLOCK(est_tree_lock); 112 113 static void est_timer(unsigned long arg) 114 { 115 int idx = (int)arg; 116 struct gen_estimator *e; 117 118 rcu_read_lock(); 119 list_for_each_entry_rcu(e, &elist[idx].list, list) { 120 struct gnet_stats_basic_packed b = {0}; 121 unsigned long rate; 122 u64 brate; 123 124 spin_lock(e->stats_lock); 125 read_lock(&est_lock); 126 if (e->bstats == NULL) 127 goto skip; 128 129 __gnet_stats_copy_basic(&b, e->cpu_bstats, e->bstats); 130 131 brate = (b.bytes - e->last_bytes)<<(7 - idx); 132 e->last_bytes = b.bytes; 133 e->avbps += (brate >> e->ewma_log) - (e->avbps >> e->ewma_log); 134 e->rate_est->bps = (e->avbps+0xF)>>5; 135 136 rate = b.packets - e->last_packets; 137 rate <<= (7 - idx); 138 e->last_packets = b.packets; 139 e->avpps += (rate >> e->ewma_log) - (e->avpps >> e->ewma_log); 140 e->rate_est->pps = (e->avpps + 0xF) >> 5; 141 skip: 142 read_unlock(&est_lock); 143 spin_unlock(e->stats_lock); 144 } 145 146 if (!list_empty(&elist[idx].list)) 147 mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx)); 148 rcu_read_unlock(); 149 } 150 151 static void gen_add_node(struct gen_estimator *est) 152 { 153 struct rb_node **p = &est_root.rb_node, *parent = NULL; 154 155 while (*p) { 156 struct gen_estimator *e; 157 158 parent = *p; 159 e = rb_entry(parent, struct gen_estimator, node); 160 161 if (est->bstats > e->bstats) 162 p = &parent->rb_right; 163 else 164 p = &parent->rb_left; 165 } 166 rb_link_node(&est->node, parent, p); 167 rb_insert_color(&est->node, &est_root); 168 } 169 170 static 171 struct gen_estimator *gen_find_node(const struct gnet_stats_basic_packed *bstats, 172 const struct gnet_stats_rate_est64 *rate_est) 173 { 174 struct rb_node *p = est_root.rb_node; 175 176 while (p) { 177 struct gen_estimator *e; 178 179 e = rb_entry(p, struct gen_estimator, node); 180 181 if (bstats > e->bstats) 182 p = p->rb_right; 183 else if (bstats < e->bstats || rate_est != e->rate_est) 184 p = p->rb_left; 185 else 186 return e; 187 } 188 return NULL; 189 } 190 191 /** 192 * gen_new_estimator - create a new rate estimator 193 * @bstats: basic statistics 194 * @rate_est: rate estimator statistics 195 * @stats_lock: statistics lock 196 * @opt: rate estimator configuration TLV 197 * 198 * Creates a new rate estimator with &bstats as source and &rate_est 199 * as destination. A new timer with the interval specified in the 200 * configuration TLV is created. Upon each interval, the latest statistics 201 * will be read from &bstats and the estimated rate will be stored in 202 * &rate_est with the statistics lock grabbed during this period. 203 * 204 * Returns 0 on success or a negative error code. 205 * 206 */ 207 int gen_new_estimator(struct gnet_stats_basic_packed *bstats, 208 struct gnet_stats_basic_cpu __percpu *cpu_bstats, 209 struct gnet_stats_rate_est64 *rate_est, 210 spinlock_t *stats_lock, 211 struct nlattr *opt) 212 { 213 struct gen_estimator *est; 214 struct gnet_estimator *parm = nla_data(opt); 215 struct gnet_stats_basic_packed b = {0}; 216 int idx; 217 218 if (nla_len(opt) < sizeof(*parm)) 219 return -EINVAL; 220 221 if (parm->interval < -2 || parm->interval > 3) 222 return -EINVAL; 223 224 est = kzalloc(sizeof(*est), GFP_KERNEL); 225 if (est == NULL) 226 return -ENOBUFS; 227 228 __gnet_stats_copy_basic(&b, cpu_bstats, bstats); 229 230 idx = parm->interval + 2; 231 est->bstats = bstats; 232 est->rate_est = rate_est; 233 est->stats_lock = stats_lock; 234 est->ewma_log = parm->ewma_log; 235 est->last_bytes = b.bytes; 236 est->avbps = rate_est->bps<<5; 237 est->last_packets = b.packets; 238 est->avpps = rate_est->pps<<10; 239 est->cpu_bstats = cpu_bstats; 240 241 spin_lock_bh(&est_tree_lock); 242 if (!elist[idx].timer.function) { 243 INIT_LIST_HEAD(&elist[idx].list); 244 setup_timer(&elist[idx].timer, est_timer, idx); 245 } 246 247 if (list_empty(&elist[idx].list)) 248 mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx)); 249 250 list_add_rcu(&est->list, &elist[idx].list); 251 gen_add_node(est); 252 spin_unlock_bh(&est_tree_lock); 253 254 return 0; 255 } 256 EXPORT_SYMBOL(gen_new_estimator); 257 258 /** 259 * gen_kill_estimator - remove a rate estimator 260 * @bstats: basic statistics 261 * @rate_est: rate estimator statistics 262 * 263 * Removes the rate estimator specified by &bstats and &rate_est. 264 * 265 * Note : Caller should respect an RCU grace period before freeing stats_lock 266 */ 267 void gen_kill_estimator(struct gnet_stats_basic_packed *bstats, 268 struct gnet_stats_rate_est64 *rate_est) 269 { 270 struct gen_estimator *e; 271 272 spin_lock_bh(&est_tree_lock); 273 while ((e = gen_find_node(bstats, rate_est))) { 274 rb_erase(&e->node, &est_root); 275 276 write_lock(&est_lock); 277 e->bstats = NULL; 278 write_unlock(&est_lock); 279 280 list_del_rcu(&e->list); 281 kfree_rcu(e, e_rcu); 282 } 283 spin_unlock_bh(&est_tree_lock); 284 } 285 EXPORT_SYMBOL(gen_kill_estimator); 286 287 /** 288 * gen_replace_estimator - replace rate estimator configuration 289 * @bstats: basic statistics 290 * @rate_est: rate estimator statistics 291 * @stats_lock: statistics lock 292 * @opt: rate estimator configuration TLV 293 * 294 * Replaces the configuration of a rate estimator by calling 295 * gen_kill_estimator() and gen_new_estimator(). 296 * 297 * Returns 0 on success or a negative error code. 298 */ 299 int gen_replace_estimator(struct gnet_stats_basic_packed *bstats, 300 struct gnet_stats_basic_cpu __percpu *cpu_bstats, 301 struct gnet_stats_rate_est64 *rate_est, 302 spinlock_t *stats_lock, struct nlattr *opt) 303 { 304 gen_kill_estimator(bstats, rate_est); 305 return gen_new_estimator(bstats, cpu_bstats, rate_est, stats_lock, opt); 306 } 307 EXPORT_SYMBOL(gen_replace_estimator); 308 309 /** 310 * gen_estimator_active - test if estimator is currently in use 311 * @bstats: basic statistics 312 * @rate_est: rate estimator statistics 313 * 314 * Returns true if estimator is active, and false if not. 315 */ 316 bool gen_estimator_active(const struct gnet_stats_basic_packed *bstats, 317 const struct gnet_stats_rate_est64 *rate_est) 318 { 319 bool res; 320 321 ASSERT_RTNL(); 322 323 spin_lock_bh(&est_tree_lock); 324 res = gen_find_node(bstats, rate_est) != NULL; 325 spin_unlock_bh(&est_tree_lock); 326 327 return res; 328 } 329 EXPORT_SYMBOL(gen_estimator_active); 330