git.oblomov.eu Git - linux-2.6/blob - 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 ctl_table vs_table[] = {
 127         {
 128                 .procname       = "vs",
 129                 .mode           = 0555,
 130                 .child          = vs_vars_table
 131         },
 132         { .ctl_name = 0 }
 133 };
 134
 135 static ctl_table ipvs_ipv4_table[] = {
 136         {
 137                 .ctl_name       = NET_IPV4,
 138                 .procname       = "ipv4",
 139                 .mode           = 0555,
 140                 .child          = vs_table
 141         },
 142         { .ctl_name = 0 }
 143 };
 144
 145 static ctl_table lblc_root_table[] = {
 146         {
 147                 .ctl_name       = CTL_NET,
 148                 .procname       = "net",
 149                 .mode           = 0555,
 150                 .child          = ipvs_ipv4_table
 151         },
 152         { .ctl_name = 0 }
 153 };
 154
 155 static struct ctl_table_header * sysctl_header;
 156
 157 /*
 158  *      new/free a ip_vs_lblc_entry, which is a mapping of a destionation
 159  *      IP address to a server.
 160  */
 161 static inline struct ip_vs_lblc_entry *
 162 ip_vs_lblc_new(__be32 daddr, struct ip_vs_dest *dest)
 163 {
 164         struct ip_vs_lblc_entry *en;
 165
 166         en = kmalloc(sizeof(struct ip_vs_lblc_entry), GFP_ATOMIC);
 167         if (en == NULL) {
 168                 IP_VS_ERR("ip_vs_lblc_new(): no memory\n");
 169                 return NULL;
 170         }
 171
 172         INIT_LIST_HEAD(&en->list);
 173         en->addr = daddr;
 174
 175         atomic_inc(&dest->refcnt);
 176         en->dest = dest;
 177
 178         return en;
 179 }
 180
 181
 182 static inline void ip_vs_lblc_free(struct ip_vs_lblc_entry *en)
 183 {
 184         list_del(&en->list);
 185         /*
 186          * We don't kfree dest because it is refered either by its service
 187          * or the trash dest list.
 188          */
 189         atomic_dec(&en->dest->refcnt);
 190         kfree(en);
 191 }
 192
 193
 194 /*
 195  *      Returns hash value for IPVS LBLC entry
 196  */
 197 static inline unsigned ip_vs_lblc_hashkey(__be32 addr)
 198 {
 199         return (ntohl(addr)*2654435761UL) & IP_VS_LBLC_TAB_MASK;
 200 }
 201
 202
 203 /*
 204  *      Hash an entry in the ip_vs_lblc_table.
 205  *      returns bool success.
 206  */
 207 static int
 208 ip_vs_lblc_hash(struct ip_vs_lblc_table *tbl, struct ip_vs_lblc_entry *en)
 209 {
 210         unsigned hash;
 211
 212         if (!list_empty(&en->list)) {
 213                 IP_VS_ERR("ip_vs_lblc_hash(): request for already hashed, "
 214                           "called from %p\n", __builtin_return_address(0));
 215                 return 0;
 216         }
 217
 218         /*
 219          *      Hash by destination IP address
 220          */
 221         hash = ip_vs_lblc_hashkey(en->addr);
 222
 223         write_lock(&tbl->lock);
 224         list_add(&en->list, &tbl->bucket[hash]);
 225         atomic_inc(&tbl->entries);
 226         write_unlock(&tbl->lock);
 227
 228         return 1;
 229 }
 230
 231
 232 /*
 233  *  Get ip_vs_lblc_entry associated with supplied parameters.
 234  */
 235 static inline struct ip_vs_lblc_entry *
 236 ip_vs_lblc_get(struct ip_vs_lblc_table *tbl, __be32 addr)
 237 {
 238         unsigned hash;
 239         struct ip_vs_lblc_entry *en;
 240
 241         hash = ip_vs_lblc_hashkey(addr);
 242
 243         read_lock(&tbl->lock);
 244
 245         list_for_each_entry(en, &tbl->bucket[hash], list) {
 246                 if (en->addr == addr) {
 247                         /* HIT */
 248                         read_unlock(&tbl->lock);
 249                         return en;
 250                 }
 251         }
 252
 253         read_unlock(&tbl->lock);
 254
 255         return NULL;
 256 }
 257
 258
 259 /*
 260  *      Flush all the entries of the specified table.
 261  */
 262 static void ip_vs_lblc_flush(struct ip_vs_lblc_table *tbl)
 263 {
 264         int i;
 265         struct ip_vs_lblc_entry *en, *nxt;
 266
 267         for (i=0; i<IP_VS_LBLC_TAB_SIZE; i++) {
 268                 write_lock(&tbl->lock);
 269                 list_for_each_entry_safe(en, nxt, &tbl->bucket[i], list) {
 270                         ip_vs_lblc_free(en);
 271                         atomic_dec(&tbl->entries);
 272                 }
 273                 write_unlock(&tbl->lock);
 274         }
 275 }
 276
 277
 278 static inline void ip_vs_lblc_full_check(struct ip_vs_lblc_table *tbl)
 279 {
 280         unsigned long now = jiffies;
 281         int i, j;
 282         struct ip_vs_lblc_entry *en, *nxt;
 283
 284         for (i=0, j=tbl->rover; i<IP_VS_LBLC_TAB_SIZE; i++) {
 285                 j = (j + 1) & IP_VS_LBLC_TAB_MASK;
 286
 287                 write_lock(&tbl->lock);
 288                 list_for_each_entry_safe(en, nxt, &tbl->bucket[j], list) {
 289                         if (time_before(now,
 290                                         en->lastuse + sysctl_ip_vs_lblc_expiration))
 291                                 continue;
 292
 293                         ip_vs_lblc_free(en);
 294                         atomic_dec(&tbl->entries);
 295                 }
 296                 write_unlock(&tbl->lock);
 297         }
 298         tbl->rover = j;
 299 }
 300
 301
 302 /*
 303  *      Periodical timer handler for IPVS lblc table
 304  *      It is used to collect stale entries when the number of entries
 305  *      exceeds the maximum size of the table.
 306  *
 307  *      Fixme: we probably need more complicated algorithm to collect
 308  *             entries that have not been used for a long time even
 309  *             if the number of entries doesn't exceed the maximum size
 310  *             of the table.
 311  *      The full expiration check is for this purpose now.
 312  */
 313 static void ip_vs_lblc_check_expire(unsigned long data)
 314 {
 315         struct ip_vs_lblc_table *tbl;
 316         unsigned long now = jiffies;
 317         int goal;
 318         int i, j;
 319         struct ip_vs_lblc_entry *en, *nxt;
 320
 321         tbl = (struct ip_vs_lblc_table *)data;
 322
 323         if ((tbl->counter % COUNT_FOR_FULL_EXPIRATION) == 0) {
 324                 /* do full expiration check */
 325                 ip_vs_lblc_full_check(tbl);
 326                 tbl->counter = 1;
 327                 goto out;
 328         }
 329
 330         if (atomic_read(&tbl->entries) <= tbl->max_size) {
 331                 tbl->counter++;
 332                 goto out;
 333         }
 334
 335         goal = (atomic_read(&tbl->entries) - tbl->max_size)*4/3;
 336         if (goal > tbl->max_size/2)
 337                 goal = tbl->max_size/2;
 338
 339         for (i=0, j=tbl->rover; i<IP_VS_LBLC_TAB_SIZE; i++) {
 340                 j = (j + 1) & IP_VS_LBLC_TAB_MASK;
 341
 342                 write_lock(&tbl->lock);
 343                 list_for_each_entry_safe(en, nxt, &tbl->bucket[j], list) {
 344                         if (time_before(now, en->lastuse + ENTRY_TIMEOUT))
 345                                 continue;
 346
 347                         ip_vs_lblc_free(en);
 348                         atomic_dec(&tbl->entries);
 349                         goal--;
 350                 }
 351                 write_unlock(&tbl->lock);
 352                 if (goal <= 0)
 353                         break;
 354         }
 355         tbl->rover = j;
 356
 357   out:
 358         mod_timer(&tbl->periodic_timer, jiffies+CHECK_EXPIRE_INTERVAL);
 359 }
 360
 361
 362 static int ip_vs_lblc_init_svc(struct ip_vs_service *svc)
 363 {
 364         int i;
 365         struct ip_vs_lblc_table *tbl;
 366
 367         /*
 368          *    Allocate the ip_vs_lblc_table for this service
 369          */
 370         tbl = kmalloc(sizeof(struct ip_vs_lblc_table), GFP_ATOMIC);
 371         if (tbl == NULL) {
 372                 IP_VS_ERR("ip_vs_lblc_init_svc(): no memory\n");
 373                 return -ENOMEM;
 374         }
 375         svc->sched_data = tbl;
 376         IP_VS_DBG(6, "LBLC hash table (memory=%Zdbytes) allocated for "
 377                   "current service\n",
 378                   sizeof(struct ip_vs_lblc_table));
 379
 380         /*
 381          *    Initialize the hash buckets
 382          */
 383         for (i=0; i<IP_VS_LBLC_TAB_SIZE; i++) {
 384                 INIT_LIST_HEAD(&tbl->bucket[i]);
 385         }
 386         rwlock_init(&tbl->lock);
 387         tbl->max_size = IP_VS_LBLC_TAB_SIZE*16;
 388         tbl->rover = 0;
 389         tbl->counter = 1;
 390
 391         /*
 392          *    Hook periodic timer for garbage collection
 393          */
 394         init_timer(&tbl->periodic_timer);
 395         tbl->periodic_timer.data = (unsigned long)tbl;
 396         tbl->periodic_timer.function = ip_vs_lblc_check_expire;
 397         tbl->periodic_timer.expires = jiffies+CHECK_EXPIRE_INTERVAL;
 398         add_timer(&tbl->periodic_timer);
 399
 400         return 0;
 401 }
 402
 403
 404 static int ip_vs_lblc_done_svc(struct ip_vs_service *svc)
 405 {
 406         struct ip_vs_lblc_table *tbl = svc->sched_data;
 407
 408         /* remove periodic timer */
 409         del_timer_sync(&tbl->periodic_timer);
 410
 411         /* got to clean up table entries here */
 412         ip_vs_lblc_flush(tbl);
 413
 414         /* release the table itself */
 415         kfree(svc->sched_data);
 416         IP_VS_DBG(6, "LBLC hash table (memory=%Zdbytes) released\n",
 417                   sizeof(struct ip_vs_lblc_table));
 418
 419         return 0;
 420 }
 421
 422
 423 static int ip_vs_lblc_update_svc(struct ip_vs_service *svc)
 424 {
 425         return 0;
 426 }
 427
 428
 429 static inline struct ip_vs_dest *
 430 __ip_vs_wlc_schedule(struct ip_vs_service *svc, struct iphdr *iph)
 431 {
 432         struct ip_vs_dest *dest, *least;
 433         int loh, doh;
 434
 435         /*
 436          * We think the overhead of processing active connections is fifty
 437          * times higher than that of inactive connections in average. (This
 438          * fifty times might not be accurate, we will change it later.) We
 439          * use the following formula to estimate the overhead:
 440          *                dest->activeconns*50 + dest->inactconns
 441          * and the load:
 442          *                (dest overhead) / dest->weight
 443          *
 444          * Remember -- no floats in kernel mode!!!
 445          * The comparison of h1*w2 > h2*w1 is equivalent to that of
 446          *                h1/w1 > h2/w2
 447          * if every weight is larger than zero.
 448          *
 449          * The server with weight=0 is quiesced and will not receive any
 450          * new connection.
 451          */
 452         list_for_each_entry(dest, &svc->destinations, n_list) {
 453                 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
 454                         continue;
 455                 if (atomic_read(&dest->weight) > 0) {
 456                         least = dest;
 457                         loh = atomic_read(&least->activeconns) * 50
 458                                 + atomic_read(&least->inactconns);
 459                         goto nextstage;
 460                 }
 461         }
 462         return NULL;
 463
 464         /*
 465          *    Find the destination with the least load.
 466          */
 467   nextstage:
 468         list_for_each_entry_continue(dest, &svc->destinations, n_list) {
 469                 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
 470                         continue;
 471
 472                 doh = atomic_read(&dest->activeconns) * 50
 473                         + atomic_read(&dest->inactconns);
 474                 if (loh * atomic_read(&dest->weight) >
 475                     doh * atomic_read(&least->weight)) {
 476                         least = dest;
 477                         loh = doh;
 478                 }
 479         }
 480
 481         IP_VS_DBG(6, "LBLC: server %d.%d.%d.%d:%d "
 482                   "activeconns %d refcnt %d weight %d overhead %d\n",
 483                   NIPQUAD(least->addr), ntohs(least->port),
 484                   atomic_read(&least->activeconns),
 485                   atomic_read(&least->refcnt),
 486                   atomic_read(&least->weight), loh);
 487
 488         return least;
 489 }
 490
 491
 492 /*
 493  *   If this destination server is overloaded and there is a less loaded
 494  *   server, then return true.
 495  */
 496 static inline int
 497 is_overloaded(struct ip_vs_dest *dest, struct ip_vs_service *svc)
 498 {
 499         if (atomic_read(&dest->activeconns) > atomic_read(&dest->weight)) {
 500                 struct ip_vs_dest *d;
 501
 502                 list_for_each_entry(d, &svc->destinations, n_list) {
 503                         if (atomic_read(&d->activeconns)*2
 504                             < atomic_read(&d->weight)) {
 505                                 return 1;
 506                         }
 507                 }
 508         }
 509         return 0;
 510 }
 511
 512
 513 /*
 514  *    Locality-Based (weighted) Least-Connection scheduling
 515  */
 516 static struct ip_vs_dest *
 517 ip_vs_lblc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
 518 {
 519         struct ip_vs_dest *dest;
 520         struct ip_vs_lblc_table *tbl;
 521         struct ip_vs_lblc_entry *en;
 522         struct iphdr *iph = ip_hdr(skb);
 523
 524         IP_VS_DBG(6, "ip_vs_lblc_schedule(): Scheduling...\n");
 525
 526         tbl = (struct ip_vs_lblc_table *)svc->sched_data;
 527         en = ip_vs_lblc_get(tbl, iph->daddr);
 528         if (en == NULL) {
 529                 dest = __ip_vs_wlc_schedule(svc, iph);
 530                 if (dest == NULL) {
 531                         IP_VS_DBG(1, "no destination available\n");
 532                         return NULL;
 533                 }
 534                 en = ip_vs_lblc_new(iph->daddr, dest);
 535                 if (en == NULL) {
 536                         return NULL;
 537                 }
 538                 ip_vs_lblc_hash(tbl, en);
 539         } else {
 540                 dest = en->dest;
 541                 if (!(dest->flags & IP_VS_DEST_F_AVAILABLE)
 542                     || atomic_read(&dest->weight) <= 0
 543                     || is_overloaded(dest, svc)) {
 544                         dest = __ip_vs_wlc_schedule(svc, iph);
 545                         if (dest == NULL) {
 546                                 IP_VS_DBG(1, "no destination available\n");
 547                                 return NULL;
 548                         }
 549                         atomic_dec(&en->dest->refcnt);
 550                         atomic_inc(&dest->refcnt);
 551                         en->dest = dest;
 552                 }
 553         }
 554         en->lastuse = jiffies;
 555
 556         IP_VS_DBG(6, "LBLC: destination IP address %u.%u.%u.%u "
 557                   "--> server %u.%u.%u.%u:%d\n",
 558                   NIPQUAD(en->addr),
 559                   NIPQUAD(dest->addr),
 560                   ntohs(dest->port));
 561
 562         return dest;
 563 }
 564
 565
 566 /*
 567  *      IPVS LBLC Scheduler structure
 568  */
 569 static struct ip_vs_scheduler ip_vs_lblc_scheduler =
 570 {
 571         .name =                 "lblc",
 572         .refcnt =               ATOMIC_INIT(0),
 573         .module =               THIS_MODULE,
 574         .init_service =         ip_vs_lblc_init_svc,
 575         .done_service =         ip_vs_lblc_done_svc,
 576         .update_service =       ip_vs_lblc_update_svc,
 577         .schedule =             ip_vs_lblc_schedule,
 578 };
 579
 580
 581 static int __init ip_vs_lblc_init(void)
 582 {
 583         INIT_LIST_HEAD(&ip_vs_lblc_scheduler.n_list);
 584         sysctl_header = register_sysctl_table(lblc_root_table);
 585         return register_ip_vs_scheduler(&ip_vs_lblc_scheduler);
 586 }
 587
 588
 589 static void __exit ip_vs_lblc_cleanup(void)
 590 {
 591         unregister_sysctl_table(sysctl_header);
 592         unregister_ip_vs_scheduler(&ip_vs_lblc_scheduler);
 593 }
 594
 595
 596 module_init(ip_vs_lblc_init);
 597 module_exit(ip_vs_lblc_cleanup);
 598 MODULE_LICENSE("GPL");