net/ipv4/ipvs/ip_vs_lblc.c

   1 /*
   2  * IPVS:        Locality-Based Least-Connection scheduling module
   3  *
   4  * Version:     $Id: ip_vs_lblc.c,v 1.10 2002/09/15 08:14:08 wensong Exp $
   5  *
   6  * Authors:     Wensong Zhang <wensong@gnuchina.org>
   7  *
   8  *              This program is free software; you can redistribute it and/or
   9  *              modify it under the terms of the GNU General Public License
  10  *              as published by the Free Software Foundation; either version
  11  *              2 of the License, or (at your option) any later version.
  12  *
  13  * Changes:
  14  *     Martin Hamilton         :    fixed the terrible locking bugs
  15  *                                   *lock(tbl->lock) ==> *lock(&tbl->lock)
  16  *     Wensong Zhang           :    fixed the uninitilized tbl->lock bug
  17  *     Wensong Zhang           :    added doing full expiration check to
  18  *                                   collect stale entries of 24+ hours when
  19  *                                   no partial expire check in a half hour
  20  *     Julian Anastasov        :    replaced del_timer call with del_timer_sync
  21  *                                   to avoid the possible race between timer
  22  *                                   handler and del_timer thread in SMP
  23  *
  24  */
  25
  26 /*
  27  * The lblc algorithm is as follows (pseudo code):
  28  *
  29  *       if cachenode[dest_ip] is null then
  30  *               n, cachenode[dest_ip] <- {weighted least-conn node};
  31  *       else
  32  *               n <- cachenode[dest_ip];
  33  *               if (n is dead) OR
  34  *                  (n.conns>n.weight AND
  35  *                   there is a node m with m.conns<m.weight/2) then
  36  *                 n, cachenode[dest_ip] <- {weighted least-conn node};
  37  *
  38  *       return n;
  39  *
  40  * Thanks must go to Wenzhuo Zhang for talking WCCP to me and pushing
  41  * me to write this module.
  42  */
  43
  44 #include <linux/ip.h>
  45 #include <linux/module.h>
  46 #include <linux/kernel.h>
  47 #include <linux/skbuff.h>
  48 #include <linux/jiffies.h>
  49
  50 /* for sysctl */
  51 #include <linux/fs.h>
  52 #include <linux/sysctl.h>
  53
  54 #include <net/ip_vs.h>
  55
  56
  57 /*
  58  *    It is for garbage collection of stale IPVS lblc entries,
  59  *    when the table is full.
  60  */
  61 #define CHECK_EXPIRE_INTERVAL   (60*HZ)
  62 #define ENTRY_TIMEOUT           (6*60*HZ)
  63
  64 /*
  65  *    It is for full expiration check.
  66  *    When there is no partial expiration check (garbage collection)
  67  *    in a half hour, do a full expiration check to collect stale
  68  *    entries that haven't been touched for a day.
  69  */
  70 #define COUNT_FOR_FULL_EXPIRATION   30
  71 static int sysctl_ip_vs_lblc_expiration = 24*60*60*HZ;
  72
  73
  74 /*
  75  *     for IPVS lblc entry hash table
  76  */
  77 #ifndef CONFIG_IP_VS_LBLC_TAB_BITS
  78 #define CONFIG_IP_VS_LBLC_TAB_BITS      10
  79 #endif
  80 #define IP_VS_LBLC_TAB_BITS     CONFIG_IP_VS_LBLC_TAB_BITS
  81 #define IP_VS_LBLC_TAB_SIZE     (1 << IP_VS_LBLC_TAB_BITS)
  82 #define IP_VS_LBLC_TAB_MASK     (IP_VS_LBLC_TAB_SIZE - 1)
  83
  84
  85 /*
  86  *      IPVS lblc entry represents an association between destination
  87  *      IP address and its destination server
  88  */
  89 struct ip_vs_lblc_entry {
  90         struct list_head        list;
  91         __be32                  addr;           /* destination IP address */
  92         struct ip_vs_dest       *dest;          /* real server (cache) */
  93         unsigned long           lastuse;        /* last used time */
  94 };
  95
  96
  97 /*
  98  *      IPVS lblc hash table
  99  */
 100 struct ip_vs_lblc_table {
 101         rwlock_t                lock;           /* lock for this table */
 102         struct list_head        bucket[IP_VS_LBLC_TAB_SIZE];  /* hash bucket */
 103         atomic_t                entries;        /* number of entries */
 104         int                     max_size;       /* maximum size of entries */
 105         struct timer_list       periodic_timer; /* collect stale entries */
 106         int                     rover;          /* rover for expire check */
 107         int                     counter;        /* counter for no expire */
 108 };
 109
 110
 111 /*
 112  *      IPVS LBLC sysctl table
 113  */
 114
 115 static ctl_table vs_vars_table[] = {
 116         {
 117                 .ctl_name       = NET_IPV4_VS_LBLC_EXPIRE,
 118                 .procname       = "lblc_expiration",
 119                 .data           = &sysctl_ip_vs_lblc_expiration,
 120                 .maxlen         = sizeof(int),
 121                 .mode           = 0644,
 122                 .proc_handler   = &proc_dointvec_jiffies,
 123         },
 124         { .ctl_name = 0 }
 125 };
 126
 127 static ctl_table vs_table[] = {
 128         {
 129                 .ctl_name       = NET_IPV4_VS,
 130                 .procname       = "vs",
 131                 .mode           = 0555,
 132                 .child          = vs_vars_table
 133         },
 134         { .ctl_name = 0 }
 135 };
 136
 137 static ctl_table ipvs_ipv4_table[] = {
 138         {
 139                 .ctl_name       = NET_IPV4,
 140                 .procname       = "ipv4",
 141                 .mode           = 0555,
 142                 .child          = vs_table
 143         },
 144         { .ctl_name = 0 }
 145 };
 146
 147 static ctl_table lblc_root_table[] = {
 148         {
 149                 .ctl_name       = CTL_NET,
 150                 .procname       = "net",
 151                 .mode           = 0555,
 152                 .child          = ipvs_ipv4_table
 153         },
 154         { .ctl_name = 0 }
 155 };
 156
 157 static struct ctl_table_header * sysctl_header;
 158
 159 /*
 160  *      new/free a ip_vs_lblc_entry, which is a mapping of a destionation
 161  *      IP address to a server.
 162  */
 163 static inline struct ip_vs_lblc_entry *
 164 ip_vs_lblc_new(__be32 daddr, struct ip_vs_dest *dest)
 165 {
 166         struct ip_vs_lblc_entry *en;
 167
 168         en = kmalloc(sizeof(struct ip_vs_lblc_entry), GFP_ATOMIC);
 169         if (en == NULL) {
 170                 IP_VS_ERR("ip_vs_lblc_new(): no memory\n");
 171                 return NULL;
 172         }
 173
 174         INIT_LIST_HEAD(&en->list);
 175         en->addr = daddr;
 176
 177         atomic_inc(&dest->refcnt);
 178         en->dest = dest;
 179
 180         return en;
 181 }
 182
 183
 184 static inline void ip_vs_lblc_free(struct ip_vs_lblc_entry *en)
 185 {
 186         list_del(&en->list);
 187         /*
 188          * We don't kfree dest because it is refered either by its service
 189          * or the trash dest list.
 190          */
 191         atomic_dec(&en->dest->refcnt);
 192         kfree(en);
 193 }
 194
 195
 196 /*
 197  *      Returns hash value for IPVS LBLC entry
 198  */
 199 static inline unsigned ip_vs_lblc_hashkey(__be32 addr)
 200 {
 201         return (ntohl(addr)*2654435761UL) & IP_VS_LBLC_TAB_MASK;
 202 }
 203
 204
 205 /*
 206  *      Hash an entry in the ip_vs_lblc_table.
 207  *      returns bool success.
 208  */
 209 static int
 210 ip_vs_lblc_hash(struct ip_vs_lblc_table *tbl, struct ip_vs_lblc_entry *en)
 211 {
 212         unsigned hash;
 213
 214         if (!list_empty(&en->list)) {
 215                 IP_VS_ERR("ip_vs_lblc_hash(): request for already hashed, "
 216                           "called from %p\n", __builtin_return_address(0));
 217                 return 0;
 218         }
 219
 220         /*
 221          *      Hash by destination IP address
 222          */
 223         hash = ip_vs_lblc_hashkey(en->addr);
 224
 225         write_lock(&tbl->lock);
 226         list_add(&en->list, &tbl->bucket[hash]);
 227         atomic_inc(&tbl->entries);
 228         write_unlock(&tbl->lock);
 229
 230         return 1;
 231 }
 232
 233
 234 /*
 235  *  Get ip_vs_lblc_entry associated with supplied parameters.
 236  */
 237 static inline struct ip_vs_lblc_entry *
 238 ip_vs_lblc_get(struct ip_vs_lblc_table *tbl, __be32 addr)
 239 {
 240         unsigned hash;
 241         struct ip_vs_lblc_entry *en;
 242
 243         hash = ip_vs_lblc_hashkey(addr);
 244
 245         read_lock(&tbl->lock);
 246
 247         list_for_each_entry(en, &tbl->bucket[hash], list) {
 248                 if (en->addr == addr) {
 249                         /* HIT */
 250                         read_unlock(&tbl->lock);
 251                         return en;
 252                 }
 253         }
 254
 255         read_unlock(&tbl->lock);
 256
 257         return NULL;
 258 }
 259
 260
 261 /*
 262  *      Flush all the entries of the specified table.
 263  */
 264 static void ip_vs_lblc_flush(struct ip_vs_lblc_table *tbl)
 265 {
 266         int i;
 267         struct ip_vs_lblc_entry *en, *nxt;
 268
 269         for (i=0; i<IP_VS_LBLC_TAB_SIZE; i++) {
 270                 write_lock(&tbl->lock);
 271                 list_for_each_entry_safe(en, nxt, &tbl->bucket[i], list) {
 272                         ip_vs_lblc_free(en);
 273                         atomic_dec(&tbl->entries);
 274                 }
 275                 write_unlock(&tbl->lock);
 276         }
 277 }
 278
 279
 280 static inline void ip_vs_lblc_full_check(struct ip_vs_lblc_table *tbl)
 281 {
 282         unsigned long now = jiffies;
 283         int i, j;
 284         struct ip_vs_lblc_entry *en, *nxt;
 285
 286         for (i=0, j=tbl->rover; i<IP_VS_LBLC_TAB_SIZE; i++) {
 287                 j = (j + 1) & IP_VS_LBLC_TAB_MASK;
 288
 289                 write_lock(&tbl->lock);
 290                 list_for_each_entry_safe(en, nxt, &tbl->bucket[j], list) {
 291                         if (time_before(now,
 292                                         en->lastuse + sysctl_ip_vs_lblc_expiration))
 293                                 continue;
 294
 295                         ip_vs_lblc_free(en);
 296                         atomic_dec(&tbl->entries);
 297                 }
 298                 write_unlock(&tbl->lock);
 299         }
 300         tbl->rover = j;
 301 }
 302
 303
 304 /*
 305  *      Periodical timer handler for IPVS lblc table
 306  *      It is used to collect stale entries when the number of entries
 307  *      exceeds the maximum size of the table.
 308  *
 309  *      Fixme: we probably need more complicated algorithm to collect
 310  *             entries that have not been used for a long time even
 311  *             if the number of entries doesn't exceed the maximum size
 312  *             of the table.
 313  *      The full expiration check is for this purpose now.
 314  */
 315 static void ip_vs_lblc_check_expire(unsigned long data)
 316 {
 317         struct ip_vs_lblc_table *tbl;
 318         unsigned long now = jiffies;
 319         int goal;
 320         int i, j;
 321         struct ip_vs_lblc_entry *en, *nxt;
 322
 323         tbl = (struct ip_vs_lblc_table *)data;
 324
 325         if ((tbl->counter % COUNT_FOR_FULL_EXPIRATION) == 0) {
 326                 /* do full expiration check */
 327                 ip_vs_lblc_full_check(tbl);
 328                 tbl->counter = 1;
 329                 goto out;
 330         }
 331
 332         if (atomic_read(&tbl->entries) <= tbl->max_size) {
 333                 tbl->counter++;
 334                 goto out;
 335         }
 336
 337         goal = (atomic_read(&tbl->entries) - tbl->max_size)*4/3;
 338         if (goal > tbl->max_size/2)
 339                 goal = tbl->max_size/2;
 340
 341         for (i=0, j=tbl->rover; i<IP_VS_LBLC_TAB_SIZE; i++) {
 342                 j = (j + 1) & IP_VS_LBLC_TAB_MASK;
 343
 344                 write_lock(&tbl->lock);
 345                 list_for_each_entry_safe(en, nxt, &tbl->bucket[j], list) {
 346                         if (time_before(now, en->lastuse + ENTRY_TIMEOUT))
 347                                 continue;
 348
 349                         ip_vs_lblc_free(en);
 350                         atomic_dec(&tbl->entries);
 351                         goal--;
 352                 }
 353                 write_unlock(&tbl->lock);
 354                 if (goal <= 0)
 355                         break;
 356         }
 357         tbl->rover = j;
 358
 359   out:
 360         mod_timer(&tbl->periodic_timer, jiffies+CHECK_EXPIRE_INTERVAL);
 361 }
 362
 363
 364 static int ip_vs_lblc_init_svc(struct ip_vs_service *svc)
 365 {
 366         int i;
 367         struct ip_vs_lblc_table *tbl;
 368
 369         /*
 370          *    Allocate the ip_vs_lblc_table for this service
 371          */
 372         tbl = kmalloc(sizeof(struct ip_vs_lblc_table), GFP_ATOMIC);
 373         if (tbl == NULL) {
 374                 IP_VS_ERR("ip_vs_lblc_init_svc(): no memory\n");
 375                 return -ENOMEM;
 376         }
 377         svc->sched_data = tbl;
 378         IP_VS_DBG(6, "LBLC hash table (memory=%Zdbytes) allocated for "
 379                   "current service\n",
 380                   sizeof(struct ip_vs_lblc_table));
 381
 382         /*
 383          *    Initialize the hash buckets
 384          */
 385         for (i=0; i<IP_VS_LBLC_TAB_SIZE; i++) {
 386                 INIT_LIST_HEAD(&tbl->bucket[i]);
 387         }
 388         rwlock_init(&tbl->lock);
 389         tbl->max_size = IP_VS_LBLC_TAB_SIZE*16;
 390         tbl->rover = 0;
 391         tbl->counter = 1;
 392
 393         /*
 394          *    Hook periodic timer for garbage collection
 395          */
 396         init_timer(&tbl->periodic_timer);
 397         tbl->periodic_timer.data = (unsigned long)tbl;
 398         tbl->periodic_timer.function = ip_vs_lblc_check_expire;
 399         tbl->periodic_timer.expires = jiffies+CHECK_EXPIRE_INTERVAL;
 400         add_timer(&tbl->periodic_timer);
 401
 402         return 0;
 403 }
 404
 405
 406 static int ip_vs_lblc_done_svc(struct ip_vs_service *svc)
 407 {
 408         struct ip_vs_lblc_table *tbl = svc->sched_data;
 409
 410         /* remove periodic timer */
 411         del_timer_sync(&tbl->periodic_timer);
 412
 413         /* got to clean up table entries here */
 414         ip_vs_lblc_flush(tbl);
 415
 416         /* release the table itself */
 417         kfree(svc->sched_data);
 418         IP_VS_DBG(6, "LBLC hash table (memory=%Zdbytes) released\n",
 419                   sizeof(struct ip_vs_lblc_table));
 420
 421         return 0;
 422 }
 423
 424
 425 static int ip_vs_lblc_update_svc(struct ip_vs_service *svc)
 426 {
 427         return 0;
 428 }
 429
 430
 431 static inline struct ip_vs_dest *
 432 __ip_vs_wlc_schedule(struct ip_vs_service *svc, struct iphdr *iph)
 433 {
 434         struct ip_vs_dest *dest, *least;
 435         int loh, doh;
 436
 437         /*
 438          * We think the overhead of processing active connections is fifty
 439          * times higher than that of inactive connections in average. (This
 440          * fifty times might not be accurate, we will change it later.) We
 441          * use the following formula to estimate the overhead:
 442          *                dest->activeconns*50 + dest->inactconns
 443          * and the load:
 444          *                (dest overhead) / dest->weight
 445          *
 446          * Remember -- no floats in kernel mode!!!
 447          * The comparison of h1*w2 > h2*w1 is equivalent to that of
 448          *                h1/w1 > h2/w2
 449          * if every weight is larger than zero.
 450          *
 451          * The server with weight=0 is quiesced and will not receive any
 452          * new connection.
 453          */
 454         list_for_each_entry(dest, &svc->destinations, n_list) {
 455                 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
 456                         continue;
 457                 if (atomic_read(&dest->weight) > 0) {
 458                         least = dest;
 459                         loh = atomic_read(&least->activeconns) * 50
 460                                 + atomic_read(&least->inactconns);
 461                         goto nextstage;
 462                 }
 463         }
 464         return NULL;
 465
 466         /*
 467          *    Find the destination with the least load.
 468          */
 469   nextstage:
 470         list_for_each_entry_continue(dest, &svc->destinations, n_list) {
 471                 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
 472                         continue;
 473
 474                 doh = atomic_read(&dest->activeconns) * 50
 475                         + atomic_read(&dest->inactconns);
 476                 if (loh * atomic_read(&dest->weight) >
 477                     doh * atomic_read(&least->weight)) {
 478                         least = dest;
 479                         loh = doh;
 480                 }
 481         }
 482
 483         IP_VS_DBG(6, "LBLC: server %d.%d.%d.%d:%d "
 484                   "activeconns %d refcnt %d weight %d overhead %d\n",
 485                   NIPQUAD(least->addr), ntohs(least->port),
 486                   atomic_read(&least->activeconns),
 487                   atomic_read(&least->refcnt),
 488                   atomic_read(&least->weight), loh);
 489
 490         return least;
 491 }
 492
 493
 494 /*
 495  *   If this destination server is overloaded and there is a less loaded
 496  *   server, then return true.
 497  */
 498 static inline int
 499 is_overloaded(struct ip_vs_dest *dest, struct ip_vs_service *svc)
 500 {
 501         if (atomic_read(&dest->activeconns) > atomic_read(&dest->weight)) {
 502                 struct ip_vs_dest *d;
 503
 504                 list_for_each_entry(d, &svc->destinations, n_list) {
 505                         if (atomic_read(&d->activeconns)*2
 506                             < atomic_read(&d->weight)) {
 507                                 return 1;
 508                         }
 509                 }
 510         }
 511         return 0;
 512 }
 513
 514
 515 /*
 516  *    Locality-Based (weighted) Least-Connection scheduling
 517  */
 518 static struct ip_vs_dest *
 519 ip_vs_lblc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
 520 {
 521         struct ip_vs_dest *dest;
 522         struct ip_vs_lblc_table *tbl;
 523         struct ip_vs_lblc_entry *en;
 524         struct iphdr *iph = skb->nh.iph;
 525
 526         IP_VS_DBG(6, "ip_vs_lblc_schedule(): Scheduling...\n");
 527
 528         tbl = (struct ip_vs_lblc_table *)svc->sched_data;
 529         en = ip_vs_lblc_get(tbl, iph->daddr);
 530         if (en == NULL) {
 531                 dest = __ip_vs_wlc_schedule(svc, iph);
 532                 if (dest == NULL) {
 533                         IP_VS_DBG(1, "no destination available\n");
 534                         return NULL;
 535                 }
 536                 en = ip_vs_lblc_new(iph->daddr, dest);
 537                 if (en == NULL) {
 538                         return NULL;
 539                 }
 540                 ip_vs_lblc_hash(tbl, en);
 541         } else {
 542                 dest = en->dest;
 543                 if (!(dest->flags & IP_VS_DEST_F_AVAILABLE)
 544                     || atomic_read(&dest->weight) <= 0
 545                     || is_overloaded(dest, svc)) {
 546                         dest = __ip_vs_wlc_schedule(svc, iph);
 547                         if (dest == NULL) {
 548                                 IP_VS_DBG(1, "no destination available\n");
 549                                 return NULL;
 550                         }
 551                         atomic_dec(&en->dest->refcnt);
 552                         atomic_inc(&dest->refcnt);
 553                         en->dest = dest;
 554                 }
 555         }
 556         en->lastuse = jiffies;
 557
 558         IP_VS_DBG(6, "LBLC: destination IP address %u.%u.%u.%u "
 559                   "--> server %u.%u.%u.%u:%d\n",
 560                   NIPQUAD(en->addr),
 561                   NIPQUAD(dest->addr),
 562                   ntohs(dest->port));
 563
 564         return dest;
 565 }
 566
 567
 568 /*
 569  *      IPVS LBLC Scheduler structure
 570  */
 571 static struct ip_vs_scheduler ip_vs_lblc_scheduler =
 572 {
 573         .name =                 "lblc",
 574         .refcnt =               ATOMIC_INIT(0),
 575         .module =               THIS_MODULE,
 576         .init_service =         ip_vs_lblc_init_svc,
 577         .done_service =         ip_vs_lblc_done_svc,
 578         .update_service =       ip_vs_lblc_update_svc,
 579         .schedule =             ip_vs_lblc_schedule,
 580 };
 581
 582
 583 static int __init ip_vs_lblc_init(void)
 584 {
 585         INIT_LIST_HEAD(&ip_vs_lblc_scheduler.n_list);
 586         sysctl_header = register_sysctl_table(lblc_root_table, 0);
 587         return register_ip_vs_scheduler(&ip_vs_lblc_scheduler);
 588 }
 589
 590
 591 static void __exit ip_vs_lblc_cleanup(void)
 592 {
 593         unregister_sysctl_table(sysctl_header);
 594         unregister_ip_vs_scheduler(&ip_vs_lblc_scheduler);
 595 }
 596
 597
 598 module_init(ip_vs_lblc_init);
 599 module_exit(ip_vs_lblc_cleanup);
 600 MODULE_LICENSE("GPL");