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                 .procname       = "lblc_expiration",
 118                 .data           = &sysctl_ip_vs_lblc_expiration,
 119                 .maxlen         = sizeof(int),
 120                 .mode           = 0644,
 121                 .proc_handler   = &proc_dointvec_jiffies,
 122         },
 123         { .ctl_name = 0 }
 124 };
 125
 126 static struct ctl_table_header * sysctl_header;
 127
 128 /*
 129  *      new/free a ip_vs_lblc_entry, which is a mapping of a destionation
 130  *      IP address to a server.
 131  */
 132 static inline struct ip_vs_lblc_entry *
 133 ip_vs_lblc_new(__be32 daddr, struct ip_vs_dest *dest)
 134 {
 135         struct ip_vs_lblc_entry *en;
 136
 137         en = kmalloc(sizeof(struct ip_vs_lblc_entry), GFP_ATOMIC);
 138         if (en == NULL) {
 139                 IP_VS_ERR("ip_vs_lblc_new(): no memory\n");
 140                 return NULL;
 141         }
 142
 143         INIT_LIST_HEAD(&en->list);
 144         en->addr = daddr;
 145
 146         atomic_inc(&dest->refcnt);
 147         en->dest = dest;
 148
 149         return en;
 150 }
 151
 152
 153 static inline void ip_vs_lblc_free(struct ip_vs_lblc_entry *en)
 154 {
 155         list_del(&en->list);
 156         /*
 157          * We don't kfree dest because it is refered either by its service
 158          * or the trash dest list.
 159          */
 160         atomic_dec(&en->dest->refcnt);
 161         kfree(en);
 162 }
 163
 164
 165 /*
 166  *      Returns hash value for IPVS LBLC entry
 167  */
 168 static inline unsigned ip_vs_lblc_hashkey(__be32 addr)
 169 {
 170         return (ntohl(addr)*2654435761UL) & IP_VS_LBLC_TAB_MASK;
 171 }
 172
 173
 174 /*
 175  *      Hash an entry in the ip_vs_lblc_table.
 176  *      returns bool success.
 177  */
 178 static int
 179 ip_vs_lblc_hash(struct ip_vs_lblc_table *tbl, struct ip_vs_lblc_entry *en)
 180 {
 181         unsigned hash;
 182
 183         if (!list_empty(&en->list)) {
 184                 IP_VS_ERR("ip_vs_lblc_hash(): request for already hashed, "
 185                           "called from %p\n", __builtin_return_address(0));
 186                 return 0;
 187         }
 188
 189         /*
 190          *      Hash by destination IP address
 191          */
 192         hash = ip_vs_lblc_hashkey(en->addr);
 193
 194         write_lock(&tbl->lock);
 195         list_add(&en->list, &tbl->bucket[hash]);
 196         atomic_inc(&tbl->entries);
 197         write_unlock(&tbl->lock);
 198
 199         return 1;
 200 }
 201
 202
 203 /*
 204  *  Get ip_vs_lblc_entry associated with supplied parameters.
 205  */
 206 static inline struct ip_vs_lblc_entry *
 207 ip_vs_lblc_get(struct ip_vs_lblc_table *tbl, __be32 addr)
 208 {
 209         unsigned hash;
 210         struct ip_vs_lblc_entry *en;
 211
 212         hash = ip_vs_lblc_hashkey(addr);
 213
 214         read_lock(&tbl->lock);
 215
 216         list_for_each_entry(en, &tbl->bucket[hash], list) {
 217                 if (en->addr == addr) {
 218                         /* HIT */
 219                         read_unlock(&tbl->lock);
 220                         return en;
 221                 }
 222         }
 223
 224         read_unlock(&tbl->lock);
 225
 226         return NULL;
 227 }
 228
 229
 230 /*
 231  *      Flush all the entries of the specified table.
 232  */
 233 static void ip_vs_lblc_flush(struct ip_vs_lblc_table *tbl)
 234 {
 235         int i;
 236         struct ip_vs_lblc_entry *en, *nxt;
 237
 238         for (i=0; i<IP_VS_LBLC_TAB_SIZE; i++) {
 239                 write_lock(&tbl->lock);
 240                 list_for_each_entry_safe(en, nxt, &tbl->bucket[i], list) {
 241                         ip_vs_lblc_free(en);
 242                         atomic_dec(&tbl->entries);
 243                 }
 244                 write_unlock(&tbl->lock);
 245         }
 246 }
 247
 248
 249 static inline void ip_vs_lblc_full_check(struct ip_vs_lblc_table *tbl)
 250 {
 251         unsigned long now = jiffies;
 252         int i, j;
 253         struct ip_vs_lblc_entry *en, *nxt;
 254
 255         for (i=0, j=tbl->rover; i<IP_VS_LBLC_TAB_SIZE; i++) {
 256                 j = (j + 1) & IP_VS_LBLC_TAB_MASK;
 257
 258                 write_lock(&tbl->lock);
 259                 list_for_each_entry_safe(en, nxt, &tbl->bucket[j], list) {
 260                         if (time_before(now,
 261                                         en->lastuse + sysctl_ip_vs_lblc_expiration))
 262                                 continue;
 263
 264                         ip_vs_lblc_free(en);
 265                         atomic_dec(&tbl->entries);
 266                 }
 267                 write_unlock(&tbl->lock);
 268         }
 269         tbl->rover = j;
 270 }
 271
 272
 273 /*
 274  *      Periodical timer handler for IPVS lblc table
 275  *      It is used to collect stale entries when the number of entries
 276  *      exceeds the maximum size of the table.
 277  *
 278  *      Fixme: we probably need more complicated algorithm to collect
 279  *             entries that have not been used for a long time even
 280  *             if the number of entries doesn't exceed the maximum size
 281  *             of the table.
 282  *      The full expiration check is for this purpose now.
 283  */
 284 static void ip_vs_lblc_check_expire(unsigned long data)
 285 {
 286         struct ip_vs_lblc_table *tbl;
 287         unsigned long now = jiffies;
 288         int goal;
 289         int i, j;
 290         struct ip_vs_lblc_entry *en, *nxt;
 291
 292         tbl = (struct ip_vs_lblc_table *)data;
 293
 294         if ((tbl->counter % COUNT_FOR_FULL_EXPIRATION) == 0) {
 295                 /* do full expiration check */
 296                 ip_vs_lblc_full_check(tbl);
 297                 tbl->counter = 1;
 298                 goto out;
 299         }
 300
 301         if (atomic_read(&tbl->entries) <= tbl->max_size) {
 302                 tbl->counter++;
 303                 goto out;
 304         }
 305
 306         goal = (atomic_read(&tbl->entries) - tbl->max_size)*4/3;
 307         if (goal > tbl->max_size/2)
 308                 goal = tbl->max_size/2;
 309
 310         for (i=0, j=tbl->rover; i<IP_VS_LBLC_TAB_SIZE; i++) {
 311                 j = (j + 1) & IP_VS_LBLC_TAB_MASK;
 312
 313                 write_lock(&tbl->lock);
 314                 list_for_each_entry_safe(en, nxt, &tbl->bucket[j], list) {
 315                         if (time_before(now, en->lastuse + ENTRY_TIMEOUT))
 316                                 continue;
 317
 318                         ip_vs_lblc_free(en);
 319                         atomic_dec(&tbl->entries);
 320                         goal--;
 321                 }
 322                 write_unlock(&tbl->lock);
 323                 if (goal <= 0)
 324                         break;
 325         }
 326         tbl->rover = j;
 327
 328   out:
 329         mod_timer(&tbl->periodic_timer, jiffies+CHECK_EXPIRE_INTERVAL);
 330 }
 331
 332
 333 static int ip_vs_lblc_init_svc(struct ip_vs_service *svc)
 334 {
 335         int i;
 336         struct ip_vs_lblc_table *tbl;
 337
 338         /*
 339          *    Allocate the ip_vs_lblc_table for this service
 340          */
 341         tbl = kmalloc(sizeof(struct ip_vs_lblc_table), GFP_ATOMIC);
 342         if (tbl == NULL) {
 343                 IP_VS_ERR("ip_vs_lblc_init_svc(): no memory\n");
 344                 return -ENOMEM;
 345         }
 346         svc->sched_data = tbl;
 347         IP_VS_DBG(6, "LBLC hash table (memory=%Zdbytes) allocated for "
 348                   "current service\n",
 349                   sizeof(struct ip_vs_lblc_table));
 350
 351         /*
 352          *    Initialize the hash buckets
 353          */
 354         for (i=0; i<IP_VS_LBLC_TAB_SIZE; i++) {
 355                 INIT_LIST_HEAD(&tbl->bucket[i]);
 356         }
 357         rwlock_init(&tbl->lock);
 358         tbl->max_size = IP_VS_LBLC_TAB_SIZE*16;
 359         tbl->rover = 0;
 360         tbl->counter = 1;
 361
 362         /*
 363          *    Hook periodic timer for garbage collection
 364          */
 365         setup_timer(&tbl->periodic_timer, ip_vs_lblc_check_expire,
 366                         (unsigned long)tbl);
 367         tbl->periodic_timer.expires = jiffies+CHECK_EXPIRE_INTERVAL;
 368         add_timer(&tbl->periodic_timer);
 369
 370         return 0;
 371 }
 372
 373
 374 static int ip_vs_lblc_done_svc(struct ip_vs_service *svc)
 375 {
 376         struct ip_vs_lblc_table *tbl = svc->sched_data;
 377
 378         /* remove periodic timer */
 379         del_timer_sync(&tbl->periodic_timer);
 380
 381         /* got to clean up table entries here */
 382         ip_vs_lblc_flush(tbl);
 383
 384         /* release the table itself */
 385         kfree(svc->sched_data);
 386         IP_VS_DBG(6, "LBLC hash table (memory=%Zdbytes) released\n",
 387                   sizeof(struct ip_vs_lblc_table));
 388
 389         return 0;
 390 }
 391
 392
 393 static int ip_vs_lblc_update_svc(struct ip_vs_service *svc)
 394 {
 395         return 0;
 396 }
 397
 398
 399 static inline struct ip_vs_dest *
 400 __ip_vs_wlc_schedule(struct ip_vs_service *svc, struct iphdr *iph)
 401 {
 402         struct ip_vs_dest *dest, *least;
 403         int loh, doh;
 404
 405         /*
 406          * We think the overhead of processing active connections is fifty
 407          * times higher than that of inactive connections in average. (This
 408          * fifty times might not be accurate, we will change it later.) We
 409          * use the following formula to estimate the overhead:
 410          *                dest->activeconns*50 + dest->inactconns
 411          * and the load:
 412          *                (dest overhead) / dest->weight
 413          *
 414          * Remember -- no floats in kernel mode!!!
 415          * The comparison of h1*w2 > h2*w1 is equivalent to that of
 416          *                h1/w1 > h2/w2
 417          * if every weight is larger than zero.
 418          *
 419          * The server with weight=0 is quiesced and will not receive any
 420          * new connection.
 421          */
 422         list_for_each_entry(dest, &svc->destinations, n_list) {
 423                 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
 424                         continue;
 425                 if (atomic_read(&dest->weight) > 0) {
 426                         least = dest;
 427                         loh = atomic_read(&least->activeconns) * 50
 428                                 + atomic_read(&least->inactconns);
 429                         goto nextstage;
 430                 }
 431         }
 432         return NULL;
 433
 434         /*
 435          *    Find the destination with the least load.
 436          */
 437   nextstage:
 438         list_for_each_entry_continue(dest, &svc->destinations, n_list) {
 439                 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
 440                         continue;
 441
 442                 doh = atomic_read(&dest->activeconns) * 50
 443                         + atomic_read(&dest->inactconns);
 444                 if (loh * atomic_read(&dest->weight) >
 445                     doh * atomic_read(&least->weight)) {
 446                         least = dest;
 447                         loh = doh;
 448                 }
 449         }
 450
 451         IP_VS_DBG(6, "LBLC: server %d.%d.%d.%d:%d "
 452                   "activeconns %d refcnt %d weight %d overhead %d\n",
 453                   NIPQUAD(least->addr), ntohs(least->port),
 454                   atomic_read(&least->activeconns),
 455                   atomic_read(&least->refcnt),
 456                   atomic_read(&least->weight), loh);
 457
 458         return least;
 459 }
 460
 461
 462 /*
 463  *   If this destination server is overloaded and there is a less loaded
 464  *   server, then return true.
 465  */
 466 static inline int
 467 is_overloaded(struct ip_vs_dest *dest, struct ip_vs_service *svc)
 468 {
 469         if (atomic_read(&dest->activeconns) > atomic_read(&dest->weight)) {
 470                 struct ip_vs_dest *d;
 471
 472                 list_for_each_entry(d, &svc->destinations, n_list) {
 473                         if (atomic_read(&d->activeconns)*2
 474                             < atomic_read(&d->weight)) {
 475                                 return 1;
 476                         }
 477                 }
 478         }
 479         return 0;
 480 }
 481
 482
 483 /*
 484  *    Locality-Based (weighted) Least-Connection scheduling
 485  */
 486 static struct ip_vs_dest *
 487 ip_vs_lblc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
 488 {
 489         struct ip_vs_dest *dest;
 490         struct ip_vs_lblc_table *tbl;
 491         struct ip_vs_lblc_entry *en;
 492         struct iphdr *iph = ip_hdr(skb);
 493
 494         IP_VS_DBG(6, "ip_vs_lblc_schedule(): Scheduling...\n");
 495
 496         tbl = (struct ip_vs_lblc_table *)svc->sched_data;
 497         en = ip_vs_lblc_get(tbl, iph->daddr);
 498         if (en == NULL) {
 499                 dest = __ip_vs_wlc_schedule(svc, iph);
 500                 if (dest == NULL) {
 501                         IP_VS_DBG(1, "no destination available\n");
 502                         return NULL;
 503                 }
 504                 en = ip_vs_lblc_new(iph->daddr, dest);
 505                 if (en == NULL) {
 506                         return NULL;
 507                 }
 508                 ip_vs_lblc_hash(tbl, en);
 509         } else {
 510                 dest = en->dest;
 511                 if (!(dest->flags & IP_VS_DEST_F_AVAILABLE)
 512                     || atomic_read(&dest->weight) <= 0
 513                     || is_overloaded(dest, svc)) {
 514                         dest = __ip_vs_wlc_schedule(svc, iph);
 515                         if (dest == NULL) {
 516                                 IP_VS_DBG(1, "no destination available\n");
 517                                 return NULL;
 518                         }
 519                         atomic_dec(&en->dest->refcnt);
 520                         atomic_inc(&dest->refcnt);
 521                         en->dest = dest;
 522                 }
 523         }
 524         en->lastuse = jiffies;
 525
 526         IP_VS_DBG(6, "LBLC: destination IP address %u.%u.%u.%u "
 527                   "--> server %u.%u.%u.%u:%d\n",
 528                   NIPQUAD(en->addr),
 529                   NIPQUAD(dest->addr),
 530                   ntohs(dest->port));
 531
 532         return dest;
 533 }
 534
 535
 536 /*
 537  *      IPVS LBLC Scheduler structure
 538  */
 539 static struct ip_vs_scheduler ip_vs_lblc_scheduler =
 540 {
 541         .name =                 "lblc",
 542         .refcnt =               ATOMIC_INIT(0),
 543         .module =               THIS_MODULE,
 544         .init_service =         ip_vs_lblc_init_svc,
 545         .done_service =         ip_vs_lblc_done_svc,
 546         .update_service =       ip_vs_lblc_update_svc,
 547         .schedule =             ip_vs_lblc_schedule,
 548 };
 549
 550
 551 static int __init ip_vs_lblc_init(void)
 552 {
 553         int ret;
 554
 555         INIT_LIST_HEAD(&ip_vs_lblc_scheduler.n_list);
 556         sysctl_header = register_sysctl_paths(net_vs_ctl_path, vs_vars_table);
 557         ret = register_ip_vs_scheduler(&ip_vs_lblc_scheduler);
 558         if (ret)
 559                 unregister_sysctl_table(sysctl_header);
 560         return ret;
 561 }
 562
 563
 564 static void __exit ip_vs_lblc_cleanup(void)
 565 {
 566         unregister_sysctl_table(sysctl_header);
 567         unregister_ip_vs_scheduler(&ip_vs_lblc_scheduler);
 568 }
 569
 570
 571 module_init(ip_vs_lblc_init);
 572 module_exit(ip_vs_lblc_cleanup);
 573 MODULE_LICENSE("GPL");