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    * The stored value for avbps is scaled by 2^5, so that maximal
  70      rate is ~1Gbit, avpps is scaled by 2^10.
  71
  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         u32                     last_packets;
  90         u32                     avpps;
  91         u32                     avbps;
  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                 u32 npackets;
 119                 u32 rate;
 120
 121                 spin_lock(e->stats_lock);
 122                 read_lock(&est_lock);
 123                 if (e->bstats == NULL)
 124                         goto skip;
 125
 126                 nbytes = e->bstats->bytes;
 127                 npackets = e->bstats->packets;
 128                 rate = (nbytes - e->last_bytes)<<(7 - idx);
 129                 e->last_bytes = nbytes;
 130                 e->avbps += ((long)rate - (long)e->avbps) >> e->ewma_log;
 131                 e->rate_est->bps = (e->avbps+0xF)>>5;
 132
 133                 rate = (npackets - e->last_packets)<<(12 - idx);
 134                 e->last_packets = npackets;
 135                 e->avpps += ((long)rate - (long)e->avpps) >> e->ewma_log;
 136                 e->rate_est->pps = (e->avpps+0x1FF)>>10;
 137 skip:
 138                 read_unlock(&est_lock);
 139                 spin_unlock(e->stats_lock);
 140         }
 141
 142         if (!list_empty(&elist[idx].list))
 143                 mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx));
 144         rcu_read_unlock();
 145 }
 146
 147 static void gen_add_node(struct gen_estimator *est)
 148 {
 149         struct rb_node **p = &est_root.rb_node, *parent = NULL;
 150
 151         while (*p) {
 152                 struct gen_estimator *e;
 153
 154                 parent = *p;
 155                 e = rb_entry(parent, struct gen_estimator, node);
 156
 157                 if (est->bstats > e->bstats)
 158                         p = &parent->rb_right;
 159                 else
 160                         p = &parent->rb_left;
 161         }
 162         rb_link_node(&est->node, parent, p);
 163         rb_insert_color(&est->node, &est_root);
 164 }
 165
 166 static
 167 struct gen_estimator *gen_find_node(const struct gnet_stats_basic *bstats,
 168                                     const struct gnet_stats_rate_est *rate_est)
 169 {
 170         struct rb_node *p = est_root.rb_node;
 171
 172         while (p) {
 173                 struct gen_estimator *e;
 174
 175                 e = rb_entry(p, struct gen_estimator, node);
 176
 177                 if (bstats > e->bstats)
 178                         p = p->rb_right;
 179                 else if (bstats < e->bstats || rate_est != e->rate_est)
 180                         p = p->rb_left;
 181                 else
 182                         return e;
 183         }
 184         return NULL;
 185 }
 186
 187 /**
 188  * gen_new_estimator - create a new rate estimator
 189  * @bstats: basic statistics
 190  * @rate_est: rate estimator statistics
 191  * @stats_lock: statistics lock
 192  * @opt: rate estimator configuration TLV
 193  *
 194  * Creates a new rate estimator with &bstats as source and &rate_est
 195  * as destination. A new timer with the interval specified in the
 196  * configuration TLV is created. Upon each interval, the latest statistics
 197  * will be read from &bstats and the estimated rate will be stored in
 198  * &rate_est with the statistics lock grabed during this period.
 199  *
 200  * Returns 0 on success or a negative error code.
 201  *
 202  * NOTE: Called under rtnl_mutex
 203  */
 204 int gen_new_estimator(struct gnet_stats_basic *bstats,
 205                       struct gnet_stats_rate_est *rate_est,
 206                       spinlock_t *stats_lock,
 207                       struct nlattr *opt)
 208 {
 209         struct gen_estimator *est;
 210         struct gnet_estimator *parm = nla_data(opt);
 211         int idx;
 212
 213         if (nla_len(opt) < sizeof(*parm))
 214                 return -EINVAL;
 215
 216         if (parm->interval < -2 || parm->interval > 3)
 217                 return -EINVAL;
 218
 219         est = kzalloc(sizeof(*est), GFP_KERNEL);
 220         if (est == NULL)
 221                 return -ENOBUFS;
 222
 223         idx = parm->interval + 2;
 224         est->bstats = bstats;
 225         est->rate_est = rate_est;
 226         est->stats_lock = stats_lock;
 227         est->ewma_log = parm->ewma_log;
 228         est->last_bytes = bstats->bytes;
 229         est->avbps = rate_est->bps<<5;
 230         est->last_packets = bstats->packets;
 231         est->avpps = rate_est->pps<<10;
 232
 233         if (!elist[idx].timer.function) {
 234                 INIT_LIST_HEAD(&elist[idx].list);
 235                 setup_timer(&elist[idx].timer, est_timer, idx);
 236         }
 237
 238         if (list_empty(&elist[idx].list))
 239                 mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx));
 240
 241         list_add_rcu(&est->list, &elist[idx].list);
 242         gen_add_node(est);
 243
 244         return 0;
 245 }
 246 EXPORT_SYMBOL(gen_new_estimator);
 247
 248 static void __gen_kill_estimator(struct rcu_head *head)
 249 {
 250         struct gen_estimator *e = container_of(head,
 251                                         struct gen_estimator, e_rcu);
 252         kfree(e);
 253 }
 254
 255 /**
 256  * gen_kill_estimator - remove a rate estimator
 257  * @bstats: basic statistics
 258  * @rate_est: rate estimator statistics
 259  *
 260  * Removes the rate estimator specified by &bstats and &rate_est.
 261  *
 262  * NOTE: Called under rtnl_mutex
 263  */
 264 void gen_kill_estimator(struct gnet_stats_basic *bstats,
 265                         struct gnet_stats_rate_est *rate_est)
 266 {
 267         struct gen_estimator *e;
 268
 269         while ((e = gen_find_node(bstats, rate_est))) {
 270                 rb_erase(&e->node, &est_root);
 271
 272                 write_lock_bh(&est_lock);
 273                 e->bstats = NULL;
 274                 write_unlock_bh(&est_lock);
 275
 276                 list_del_rcu(&e->list);
 277                 call_rcu(&e->e_rcu, __gen_kill_estimator);
 278         }
 279 }
 280 EXPORT_SYMBOL(gen_kill_estimator);
 281
 282 /**
 283  * gen_replace_estimator - replace rate estimator configuration
 284  * @bstats: basic statistics
 285  * @rate_est: rate estimator statistics
 286  * @stats_lock: statistics lock
 287  * @opt: rate estimator configuration TLV
 288  *
 289  * Replaces the configuration of a rate estimator by calling
 290  * gen_kill_estimator() and gen_new_estimator().
 291  *
 292  * Returns 0 on success or a negative error code.
 293  */
 294 int gen_replace_estimator(struct gnet_stats_basic *bstats,
 295                           struct gnet_stats_rate_est *rate_est,
 296                           spinlock_t *stats_lock, struct nlattr *opt)
 297 {
 298         gen_kill_estimator(bstats, rate_est);
 299         return gen_new_estimator(bstats, rate_est, stats_lock, opt);
 300 }
 301 EXPORT_SYMBOL(gen_replace_estimator);
 302
 303 /**
 304  * gen_estimator_active - test if estimator is currently in use
 305  * @bstats: basic statistics
 306  * @rate_est: rate estimator statistics
 307  *
 308  * Returns true if estimator is active, and false if not.
 309  */
 310 bool gen_estimator_active(const struct gnet_stats_basic *bstats,
 311                           const struct gnet_stats_rate_est *rate_est)
 312 {
 313         ASSERT_RTNL();
 314
 315         return gen_find_node(bstats, rate_est) != NULL;
 316 }
 317 EXPORT_SYMBOL(gen_estimator_active);