net/core/gen_estimator.c

   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 <linux/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 <linux/rbtree.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 is scaled by 2^5, avpps is scaled by 2^10.
  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 *bstats;
  85         struct gnet_stats_rate_est      *rate_est;
  86         spinlock_t              *stats_lock;
  87         int                     ewma_log;
  88         u64                     last_bytes;
  89         u64                     avbps;
  90         u32                     last_packets;
  91         u32                     avpps;
  92         struct rcu_head         e_rcu;
  93         struct rb_node          node;
  94 };
  95
  96 struct gen_estimator_head
  97 {
  98         struct timer_list       timer;
  99         struct list_head        list;
 100 };
 101
 102 static struct gen_estimator_head elist[EST_MAX_INTERVAL+1];
 103
 104 /* Protects against NULL dereference */
 105 static DEFINE_RWLOCK(est_lock);
 106
 107 /* Protects against soft lockup during large deletion */
 108 static struct rb_root est_root = RB_ROOT;
 109
 110 static void est_timer(unsigned long arg)
 111 {
 112         int idx = (int)arg;
 113         struct gen_estimator *e;
 114
 115         rcu_read_lock();
 116         list_for_each_entry_rcu(e, &elist[idx].list, list) {
 117                 u64 nbytes;
 118                 u64 brate;
 119                 u32 npackets;
 120                 u32 rate;
 121
 122                 spin_lock(e->stats_lock);
 123                 read_lock(&est_lock);
 124                 if (e->bstats == NULL)
 125                         goto skip;
 126
 127                 nbytes = e->bstats->bytes;
 128                 npackets = e->bstats->packets;
 129                 brate = (nbytes - e->last_bytes)<<(7 - idx);
 130                 e->last_bytes = nbytes;
 131                 e->avbps += ((s64)(brate - e->avbps)) >> e->ewma_log;
 132                 e->rate_est->bps = (e->avbps+0xF)>>5;
 133
 134                 rate = (npackets - e->last_packets)<<(12 - idx);
 135                 e->last_packets = npackets;
 136                 e->avpps += ((long)rate - (long)e->avpps) >> e->ewma_log;
 137                 e->rate_est->pps = (e->avpps+0x1FF)>>10;
 138 skip:
 139                 read_unlock(&est_lock);
 140                 spin_unlock(e->stats_lock);
 141         }
 142
 143         if (!list_empty(&elist[idx].list))
 144                 mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx));
 145         rcu_read_unlock();
 146 }
 147
 148 static void gen_add_node(struct gen_estimator *est)
 149 {
 150         struct rb_node **p = &est_root.rb_node, *parent = NULL;
 151
 152         while (*p) {
 153                 struct gen_estimator *e;
 154
 155                 parent = *p;
 156                 e = rb_entry(parent, struct gen_estimator, node);
 157
 158                 if (est->bstats > e->bstats)
 159                         p = &parent->rb_right;
 160                 else
 161                         p = &parent->rb_left;
 162         }
 163         rb_link_node(&est->node, parent, p);
 164         rb_insert_color(&est->node, &est_root);
 165 }
 166
 167 static
 168 struct gen_estimator *gen_find_node(const struct gnet_stats_basic *bstats,
 169                                     const struct gnet_stats_rate_est *rate_est)
 170 {
 171         struct rb_node *p = est_root.rb_node;
 172
 173         while (p) {
 174                 struct gen_estimator *e;
 175
 176                 e = rb_entry(p, struct gen_estimator, node);
 177
 178                 if (bstats > e->bstats)
 179                         p = p->rb_right;
 180                 else if (bstats < e->bstats || rate_est != e->rate_est)
 181                         p = p->rb_left;
 182                 else
 183                         return e;
 184         }
 185         return NULL;
 186 }
 187
 188 /**
 189  * gen_new_estimator - create a new rate estimator
 190  * @bstats: basic statistics
 191  * @rate_est: rate estimator statistics
 192  * @stats_lock: statistics lock
 193  * @opt: rate estimator configuration TLV
 194  *
 195  * Creates a new rate estimator with &bstats as source and &rate_est
 196  * as destination. A new timer with the interval specified in the
 197  * configuration TLV is created. Upon each interval, the latest statistics
 198  * will be read from &bstats and the estimated rate will be stored in
 199  * &rate_est with the statistics lock grabed during this period.
 200  *
 201  * Returns 0 on success or a negative error code.
 202  *
 203  * NOTE: Called under rtnl_mutex
 204  */
 205 int gen_new_estimator(struct gnet_stats_basic *bstats,
 206                       struct gnet_stats_rate_est *rate_est,
 207                       spinlock_t *stats_lock,
 208                       struct nlattr *opt)
 209 {
 210         struct gen_estimator *est;
 211         struct gnet_estimator *parm = nla_data(opt);
 212         int idx;
 213
 214         if (nla_len(opt) < sizeof(*parm))
 215                 return -EINVAL;
 216
 217         if (parm->interval < -2 || parm->interval > 3)
 218                 return -EINVAL;
 219
 220         est = kzalloc(sizeof(*est), GFP_KERNEL);
 221         if (est == NULL)
 222                 return -ENOBUFS;
 223
 224         idx = parm->interval + 2;
 225         est->bstats = bstats;
 226         est->rate_est = rate_est;
 227         est->stats_lock = stats_lock;
 228         est->ewma_log = parm->ewma_log;
 229         est->last_bytes = bstats->bytes;
 230         est->avbps = rate_est->bps<<5;
 231         est->last_packets = bstats->packets;
 232         est->avpps = rate_est->pps<<10;
 233
 234         if (!elist[idx].timer.function) {
 235                 INIT_LIST_HEAD(&elist[idx].list);
 236                 setup_timer(&elist[idx].timer, est_timer, idx);
 237         }
 238
 239         if (list_empty(&elist[idx].list))
 240                 mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx));
 241
 242         list_add_rcu(&est->list, &elist[idx].list);
 243         gen_add_node(est);
 244
 245         return 0;
 246 }
 247 EXPORT_SYMBOL(gen_new_estimator);
 248
 249 static void __gen_kill_estimator(struct rcu_head *head)
 250 {
 251         struct gen_estimator *e = container_of(head,
 252                                         struct gen_estimator, e_rcu);
 253         kfree(e);
 254 }
 255
 256 /**
 257  * gen_kill_estimator - remove a rate estimator
 258  * @bstats: basic statistics
 259  * @rate_est: rate estimator statistics
 260  *
 261  * Removes the rate estimator specified by &bstats and &rate_est.
 262  *
 263  * NOTE: Called under rtnl_mutex
 264  */
 265 void gen_kill_estimator(struct gnet_stats_basic *bstats,
 266                         struct gnet_stats_rate_est *rate_est)
 267 {
 268         struct gen_estimator *e;
 269
 270         while ((e = gen_find_node(bstats, rate_est))) {
 271                 rb_erase(&e->node, &est_root);
 272
 273                 write_lock_bh(&est_lock);
 274                 e->bstats = NULL;
 275                 write_unlock_bh(&est_lock);
 276
 277                 list_del_rcu(&e->list);
 278                 call_rcu(&e->e_rcu, __gen_kill_estimator);
 279         }
 280 }
 281 EXPORT_SYMBOL(gen_kill_estimator);
 282
 283 /**
 284  * gen_replace_estimator - replace rate estimator configuration
 285  * @bstats: basic statistics
 286  * @rate_est: rate estimator statistics
 287  * @stats_lock: statistics lock
 288  * @opt: rate estimator configuration TLV
 289  *
 290  * Replaces the configuration of a rate estimator by calling
 291  * gen_kill_estimator() and gen_new_estimator().
 292  *
 293  * Returns 0 on success or a negative error code.
 294  */
 295 int gen_replace_estimator(struct gnet_stats_basic *bstats,
 296                           struct gnet_stats_rate_est *rate_est,
 297                           spinlock_t *stats_lock, struct nlattr *opt)
 298 {
 299         gen_kill_estimator(bstats, rate_est);
 300         return gen_new_estimator(bstats, rate_est, stats_lock, opt);
 301 }
 302 EXPORT_SYMBOL(gen_replace_estimator);
 303
 304 /**
 305  * gen_estimator_active - test if estimator is currently in use
 306  * @bstats: basic statistics
 307  * @rate_est: rate estimator statistics
 308  *
 309  * Returns true if estimator is active, and false if not.
 310  */
 311 bool gen_estimator_active(const struct gnet_stats_basic *bstats,
 312                           const struct gnet_stats_rate_est *rate_est)
 313 {
 314         ASSERT_RTNL();
 315
 316         return gen_find_node(bstats, rate_est) != NULL;
 317 }
 318 EXPORT_SYMBOL(gen_estimator_active);