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 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);