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 <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 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_packed  *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 static DEFINE_SPINLOCK(est_tree_lock);
 110
 111 static void est_timer(unsigned long arg)
 112 {
 113         int idx = (int)arg;
 114         struct gen_estimator *e;
 115
 116         rcu_read_lock();
 117         list_for_each_entry_rcu(e, &elist[idx].list, list) {
 118                 u64 nbytes;
 119                 u64 brate;
 120                 u32 npackets;
 121                 u32 rate;
 122
 123                 spin_lock(e->stats_lock);
 124                 read_lock(&est_lock);
 125                 if (e->bstats == NULL)
 126                         goto skip;
 127
 128                 nbytes = e->bstats->bytes;
 129                 npackets = e->bstats->packets;
 130                 brate = (nbytes - e->last_bytes)<<(7 - idx);
 131                 e->last_bytes = nbytes;
 132                 e->avbps += (brate >> e->ewma_log) - (e->avbps >> e->ewma_log);
 133                 e->rate_est->bps = (e->avbps+0xF)>>5;
 134
 135                 rate = (npackets - e->last_packets)<<(12 - idx);
 136                 e->last_packets = npackets;
 137                 e->avpps += (rate >> e->ewma_log) - (e->avpps >> e->ewma_log);
 138                 e->rate_est->pps = (e->avpps+0x1FF)>>10;
 139 skip:
 140                 read_unlock(&est_lock);
 141                 spin_unlock(e->stats_lock);
 142         }
 143
 144         if (!list_empty(&elist[idx].list))
 145                 mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx));
 146         rcu_read_unlock();
 147 }
 148
 149 static void gen_add_node(struct gen_estimator *est)
 150 {
 151         struct rb_node **p = &est_root.rb_node, *parent = NULL;
 152
 153         while (*p) {
 154                 struct gen_estimator *e;
 155
 156                 parent = *p;
 157                 e = rb_entry(parent, struct gen_estimator, node);
 158
 159                 if (est->bstats > e->bstats)
 160                         p = &parent->rb_right;
 161                 else
 162                         p = &parent->rb_left;
 163         }
 164         rb_link_node(&est->node, parent, p);
 165         rb_insert_color(&est->node, &est_root);
 166 }
 167
 168 static
 169 struct gen_estimator *gen_find_node(const struct gnet_stats_basic_packed *bstats,
 170                                     const struct gnet_stats_rate_est *rate_est)
 171 {
 172         struct rb_node *p = est_root.rb_node;
 173
 174         while (p) {
 175                 struct gen_estimator *e;
 176
 177                 e = rb_entry(p, struct gen_estimator, node);
 178
 179                 if (bstats > e->bstats)
 180                         p = p->rb_right;
 181                 else if (bstats < e->bstats || rate_est != e->rate_est)
 182                         p = p->rb_left;
 183                 else
 184                         return e;
 185         }
 186         return NULL;
 187 }
 188
 189 /**
 190  * gen_new_estimator - create a new rate estimator
 191  * @bstats: basic statistics
 192  * @rate_est: rate estimator statistics
 193  * @stats_lock: statistics lock
 194  * @opt: rate estimator configuration TLV
 195  *
 196  * Creates a new rate estimator with &bstats as source and &rate_est
 197  * as destination. A new timer with the interval specified in the
 198  * configuration TLV is created. Upon each interval, the latest statistics
 199  * will be read from &bstats and the estimated rate will be stored in
 200  * &rate_est with the statistics lock grabed during this period.
 201  *
 202  * Returns 0 on success or a negative error code.
 203  *
 204  */
 205 int gen_new_estimator(struct gnet_stats_basic_packed *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         spin_lock_bh(&est_tree_lock);
 235         if (!elist[idx].timer.function) {
 236                 INIT_LIST_HEAD(&elist[idx].list);
 237                 setup_timer(&elist[idx].timer, est_timer, idx);
 238         }
 239
 240         if (list_empty(&elist[idx].list))
 241                 mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx));
 242
 243         list_add_rcu(&est->list, &elist[idx].list);
 244         gen_add_node(est);
 245         spin_unlock_bh(&est_tree_lock);
 246
 247         return 0;
 248 }
 249 EXPORT_SYMBOL(gen_new_estimator);
 250
 251 /**
 252  * gen_kill_estimator - remove a rate estimator
 253  * @bstats: basic statistics
 254  * @rate_est: rate estimator statistics
 255  *
 256  * Removes the rate estimator specified by &bstats and &rate_est.
 257  *
 258  * Note : Caller should respect an RCU grace period before freeing stats_lock
 259  */
 260 void gen_kill_estimator(struct gnet_stats_basic_packed *bstats,
 261                         struct gnet_stats_rate_est *rate_est)
 262 {
 263         struct gen_estimator *e;
 264
 265         spin_lock_bh(&est_tree_lock);
 266         while ((e = gen_find_node(bstats, rate_est))) {
 267                 rb_erase(&e->node, &est_root);
 268
 269                 write_lock(&est_lock);
 270                 e->bstats = NULL;
 271                 write_unlock(&est_lock);
 272
 273                 list_del_rcu(&e->list);
 274                 kfree_rcu(e, e_rcu);
 275         }
 276         spin_unlock_bh(&est_tree_lock);
 277 }
 278 EXPORT_SYMBOL(gen_kill_estimator);
 279
 280 /**
 281  * gen_replace_estimator - replace rate estimator configuration
 282  * @bstats: basic statistics
 283  * @rate_est: rate estimator statistics
 284  * @stats_lock: statistics lock
 285  * @opt: rate estimator configuration TLV
 286  *
 287  * Replaces the configuration of a rate estimator by calling
 288  * gen_kill_estimator() and gen_new_estimator().
 289  *
 290  * Returns 0 on success or a negative error code.
 291  */
 292 int gen_replace_estimator(struct gnet_stats_basic_packed *bstats,
 293                           struct gnet_stats_rate_est *rate_est,
 294                           spinlock_t *stats_lock, struct nlattr *opt)
 295 {
 296         gen_kill_estimator(bstats, rate_est);
 297         return gen_new_estimator(bstats, rate_est, stats_lock, opt);
 298 }
 299 EXPORT_SYMBOL(gen_replace_estimator);
 300
 301 /**
 302  * gen_estimator_active - test if estimator is currently in use
 303  * @bstats: basic statistics
 304  * @rate_est: rate estimator statistics
 305  *
 306  * Returns true if estimator is active, and false if not.
 307  */
 308 bool gen_estimator_active(const struct gnet_stats_basic_packed *bstats,
 309                           const struct gnet_stats_rate_est *rate_est)
 310 {
 311         bool res;
 312
 313         ASSERT_RTNL();
 314
 315         spin_lock_bh(&est_tree_lock);
 316         res = gen_find_node(bstats, rate_est) != NULL;
 317         spin_unlock_bh(&est_tree_lock);
 318
 319         return res;
 320 }
 321 EXPORT_SYMBOL(gen_estimator_active);