2 * IPVS: Locality-Based Least-Connection scheduling module
4 * Authors: Wensong Zhang <wensong@gnuchina.org>
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
12 * Martin Hamilton : fixed the terrible locking bugs
13 * *lock(tbl->lock) ==> *lock(&tbl->lock)
14 * Wensong Zhang : fixed the uninitialized tbl->lock bug
15 * Wensong Zhang : added doing full expiration check to
16 * collect stale entries of 24+ hours when
17 * no partial expire check in a half hour
18 * Julian Anastasov : replaced del_timer call with del_timer_sync
19 * to avoid the possible race between timer
20 * handler and del_timer thread in SMP
25 * The lblc algorithm is as follows (pseudo code):
27 * if cachenode[dest_ip] is null then
28 * n, cachenode[dest_ip] <- {weighted least-conn node};
30 * n <- cachenode[dest_ip];
32 * (n.conns>n.weight AND
33 * there is a node m with m.conns<m.weight/2) then
34 * n, cachenode[dest_ip] <- {weighted least-conn node};
38 * Thanks must go to Wenzhuo Zhang for talking WCCP to me and pushing
39 * me to write this module.
42 #define KMSG_COMPONENT "IPVS"
43 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
46 #include <linux/slab.h>
47 #include <linux/module.h>
48 #include <linux/kernel.h>
49 #include <linux/skbuff.h>
50 #include <linux/jiffies.h>
54 #include <linux/sysctl.h>
56 #include <net/ip_vs.h>
60 * It is for garbage collection of stale IPVS lblc entries,
61 * when the table is full.
63 #define CHECK_EXPIRE_INTERVAL (60*HZ)
64 #define ENTRY_TIMEOUT (6*60*HZ)
66 #define DEFAULT_EXPIRATION (24*60*60*HZ)
69 * It is for full expiration check.
70 * When there is no partial expiration check (garbage collection)
71 * in a half hour, do a full expiration check to collect stale
72 * entries that haven't been touched for a day.
74 #define COUNT_FOR_FULL_EXPIRATION 30
78 * for IPVS lblc entry hash table
80 #ifndef CONFIG_IP_VS_LBLC_TAB_BITS
81 #define CONFIG_IP_VS_LBLC_TAB_BITS 10
83 #define IP_VS_LBLC_TAB_BITS CONFIG_IP_VS_LBLC_TAB_BITS
84 #define IP_VS_LBLC_TAB_SIZE (1 << IP_VS_LBLC_TAB_BITS)
85 #define IP_VS_LBLC_TAB_MASK (IP_VS_LBLC_TAB_SIZE - 1)
89 * IPVS lblc entry represents an association between destination
90 * IP address and its destination server
92 struct ip_vs_lblc_entry {
93 struct hlist_node list;
94 int af; /* address family */
95 union nf_inet_addr addr; /* destination IP address */
96 struct ip_vs_dest *dest; /* real server (cache) */
97 unsigned long lastuse; /* last used time */
98 struct rcu_head rcu_head;
103 * IPVS lblc hash table
105 struct ip_vs_lblc_table {
106 struct rcu_head rcu_head;
107 struct hlist_head bucket[IP_VS_LBLC_TAB_SIZE]; /* hash bucket */
108 struct timer_list periodic_timer; /* collect stale entries */
109 atomic_t entries; /* number of entries */
110 int max_size; /* maximum size of entries */
111 int rover; /* rover for expire check */
112 int counter; /* counter for no expire */
118 * IPVS LBLC sysctl table
121 static struct ctl_table vs_vars_table[] = {
123 .procname = "lblc_expiration",
125 .maxlen = sizeof(int),
127 .proc_handler = proc_dointvec_jiffies,
133 static void ip_vs_lblc_rcu_free(struct rcu_head *head)
135 struct ip_vs_lblc_entry *en = container_of(head,
136 struct ip_vs_lblc_entry,
139 ip_vs_dest_put(en->dest);
143 static inline void ip_vs_lblc_del(struct ip_vs_lblc_entry *en)
145 hlist_del_rcu(&en->list);
146 call_rcu(&en->rcu_head, ip_vs_lblc_rcu_free);
150 * Returns hash value for IPVS LBLC entry
152 static inline unsigned int
153 ip_vs_lblc_hashkey(int af, const union nf_inet_addr *addr)
155 __be32 addr_fold = addr->ip;
157 #ifdef CONFIG_IP_VS_IPV6
159 addr_fold = addr->ip6[0]^addr->ip6[1]^
160 addr->ip6[2]^addr->ip6[3];
162 return (ntohl(addr_fold)*2654435761UL) & IP_VS_LBLC_TAB_MASK;
167 * Hash an entry in the ip_vs_lblc_table.
168 * returns bool success.
171 ip_vs_lblc_hash(struct ip_vs_lblc_table *tbl, struct ip_vs_lblc_entry *en)
173 unsigned int hash = ip_vs_lblc_hashkey(en->af, &en->addr);
175 hlist_add_head_rcu(&en->list, &tbl->bucket[hash]);
176 atomic_inc(&tbl->entries);
180 /* Get ip_vs_lblc_entry associated with supplied parameters. */
181 static inline struct ip_vs_lblc_entry *
182 ip_vs_lblc_get(int af, struct ip_vs_lblc_table *tbl,
183 const union nf_inet_addr *addr)
185 unsigned int hash = ip_vs_lblc_hashkey(af, addr);
186 struct ip_vs_lblc_entry *en;
188 hlist_for_each_entry_rcu(en, &tbl->bucket[hash], list)
189 if (ip_vs_addr_equal(af, &en->addr, addr))
197 * Create or update an ip_vs_lblc_entry, which is a mapping of a destination IP
198 * address to a server. Called under spin lock.
200 static inline struct ip_vs_lblc_entry *
201 ip_vs_lblc_new(struct ip_vs_lblc_table *tbl, const union nf_inet_addr *daddr,
202 struct ip_vs_dest *dest)
204 struct ip_vs_lblc_entry *en;
206 en = ip_vs_lblc_get(dest->af, tbl, daddr);
208 if (en->dest == dest)
212 en = kmalloc(sizeof(*en), GFP_ATOMIC);
217 ip_vs_addr_copy(dest->af, &en->addr, daddr);
218 en->lastuse = jiffies;
220 ip_vs_dest_hold(dest);
223 ip_vs_lblc_hash(tbl, en);
230 * Flush all the entries of the specified table.
232 static void ip_vs_lblc_flush(struct ip_vs_service *svc)
234 struct ip_vs_lblc_table *tbl = svc->sched_data;
235 struct ip_vs_lblc_entry *en;
236 struct hlist_node *next;
239 spin_lock_bh(&svc->sched_lock);
241 for (i=0; i<IP_VS_LBLC_TAB_SIZE; i++) {
242 hlist_for_each_entry_safe(en, next, &tbl->bucket[i], list) {
244 atomic_dec(&tbl->entries);
247 spin_unlock_bh(&svc->sched_lock);
250 static int sysctl_lblc_expiration(struct ip_vs_service *svc)
253 struct netns_ipvs *ipvs = net_ipvs(svc->net);
254 return ipvs->sysctl_lblc_expiration;
256 return DEFAULT_EXPIRATION;
260 static inline void ip_vs_lblc_full_check(struct ip_vs_service *svc)
262 struct ip_vs_lblc_table *tbl = svc->sched_data;
263 struct ip_vs_lblc_entry *en;
264 struct hlist_node *next;
265 unsigned long now = jiffies;
268 for (i=0, j=tbl->rover; i<IP_VS_LBLC_TAB_SIZE; i++) {
269 j = (j + 1) & IP_VS_LBLC_TAB_MASK;
271 spin_lock(&svc->sched_lock);
272 hlist_for_each_entry_safe(en, next, &tbl->bucket[j], list) {
275 sysctl_lblc_expiration(svc)))
279 atomic_dec(&tbl->entries);
281 spin_unlock(&svc->sched_lock);
288 * Periodical timer handler for IPVS lblc table
289 * It is used to collect stale entries when the number of entries
290 * exceeds the maximum size of the table.
292 * Fixme: we probably need more complicated algorithm to collect
293 * entries that have not been used for a long time even
294 * if the number of entries doesn't exceed the maximum size
296 * The full expiration check is for this purpose now.
298 static void ip_vs_lblc_check_expire(unsigned long data)
300 struct ip_vs_service *svc = (struct ip_vs_service *) data;
301 struct ip_vs_lblc_table *tbl = svc->sched_data;
302 unsigned long now = jiffies;
305 struct ip_vs_lblc_entry *en;
306 struct hlist_node *next;
308 if ((tbl->counter % COUNT_FOR_FULL_EXPIRATION) == 0) {
309 /* do full expiration check */
310 ip_vs_lblc_full_check(svc);
315 if (atomic_read(&tbl->entries) <= tbl->max_size) {
320 goal = (atomic_read(&tbl->entries) - tbl->max_size)*4/3;
321 if (goal > tbl->max_size/2)
322 goal = tbl->max_size/2;
324 for (i=0, j=tbl->rover; i<IP_VS_LBLC_TAB_SIZE; i++) {
325 j = (j + 1) & IP_VS_LBLC_TAB_MASK;
327 spin_lock(&svc->sched_lock);
328 hlist_for_each_entry_safe(en, next, &tbl->bucket[j], list) {
329 if (time_before(now, en->lastuse + ENTRY_TIMEOUT))
333 atomic_dec(&tbl->entries);
336 spin_unlock(&svc->sched_lock);
343 mod_timer(&tbl->periodic_timer, jiffies+CHECK_EXPIRE_INTERVAL);
347 static int ip_vs_lblc_init_svc(struct ip_vs_service *svc)
350 struct ip_vs_lblc_table *tbl;
353 * Allocate the ip_vs_lblc_table for this service
355 tbl = kmalloc(sizeof(*tbl), GFP_KERNEL);
359 svc->sched_data = tbl;
360 IP_VS_DBG(6, "LBLC hash table (memory=%Zdbytes) allocated for "
361 "current service\n", sizeof(*tbl));
364 * Initialize the hash buckets
366 for (i=0; i<IP_VS_LBLC_TAB_SIZE; i++) {
367 INIT_HLIST_HEAD(&tbl->bucket[i]);
369 tbl->max_size = IP_VS_LBLC_TAB_SIZE*16;
375 * Hook periodic timer for garbage collection
377 setup_timer(&tbl->periodic_timer, ip_vs_lblc_check_expire,
379 mod_timer(&tbl->periodic_timer, jiffies + CHECK_EXPIRE_INTERVAL);
385 static void ip_vs_lblc_done_svc(struct ip_vs_service *svc)
387 struct ip_vs_lblc_table *tbl = svc->sched_data;
389 /* remove periodic timer */
390 del_timer_sync(&tbl->periodic_timer);
392 /* got to clean up table entries here */
393 ip_vs_lblc_flush(svc);
395 /* release the table itself */
396 kfree_rcu(tbl, rcu_head);
397 IP_VS_DBG(6, "LBLC hash table (memory=%Zdbytes) released\n",
402 static inline struct ip_vs_dest *
403 __ip_vs_lblc_schedule(struct ip_vs_service *svc)
405 struct ip_vs_dest *dest, *least;
409 * We use the following formula to estimate the load:
410 * (dest overhead) / dest->weight
412 * Remember -- no floats in kernel mode!!!
413 * The comparison of h1*w2 > h2*w1 is equivalent to that of
415 * if every weight is larger than zero.
417 * The server with weight=0 is quiesced and will not receive any
420 list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
421 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
423 if (atomic_read(&dest->weight) > 0) {
425 loh = ip_vs_dest_conn_overhead(least);
432 * Find the destination with the least load.
435 list_for_each_entry_continue_rcu(dest, &svc->destinations, n_list) {
436 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
439 doh = ip_vs_dest_conn_overhead(dest);
440 if ((__s64)loh * atomic_read(&dest->weight) >
441 (__s64)doh * atomic_read(&least->weight)) {
447 IP_VS_DBG_BUF(6, "LBLC: server %s:%d "
448 "activeconns %d refcnt %d weight %d overhead %d\n",
449 IP_VS_DBG_ADDR(least->af, &least->addr),
451 atomic_read(&least->activeconns),
452 atomic_read(&least->refcnt),
453 atomic_read(&least->weight), loh);
460 * If this destination server is overloaded and there is a less loaded
461 * server, then return true.
464 is_overloaded(struct ip_vs_dest *dest, struct ip_vs_service *svc)
466 if (atomic_read(&dest->activeconns) > atomic_read(&dest->weight)) {
467 struct ip_vs_dest *d;
469 list_for_each_entry_rcu(d, &svc->destinations, n_list) {
470 if (atomic_read(&d->activeconns)*2
471 < atomic_read(&d->weight)) {
481 * Locality-Based (weighted) Least-Connection scheduling
483 static struct ip_vs_dest *
484 ip_vs_lblc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
485 struct ip_vs_iphdr *iph)
487 struct ip_vs_lblc_table *tbl = svc->sched_data;
488 struct ip_vs_dest *dest = NULL;
489 struct ip_vs_lblc_entry *en;
491 IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
493 /* First look in our cache */
494 en = ip_vs_lblc_get(svc->af, tbl, &iph->daddr);
496 /* We only hold a read lock, but this is atomic */
497 en->lastuse = jiffies;
500 * If the destination is not available, i.e. it's in the trash,
501 * we must ignore it, as it may be removed from under our feet,
502 * if someone drops our reference count. Our caller only makes
503 * sure that destinations, that are not in the trash, are not
504 * moved to the trash, while we are scheduling. But anyone can
505 * free up entries from the trash at any time.
509 if ((dest->flags & IP_VS_DEST_F_AVAILABLE) &&
510 atomic_read(&dest->weight) > 0 && !is_overloaded(dest, svc))
514 /* No cache entry or it is invalid, time to schedule */
515 dest = __ip_vs_lblc_schedule(svc);
517 ip_vs_scheduler_err(svc, "no destination available");
521 /* If we fail to create a cache entry, we'll just use the valid dest */
522 spin_lock_bh(&svc->sched_lock);
524 ip_vs_lblc_new(tbl, &iph->daddr, dest);
525 spin_unlock_bh(&svc->sched_lock);
528 IP_VS_DBG_BUF(6, "LBLC: destination IP address %s --> server %s:%d\n",
529 IP_VS_DBG_ADDR(svc->af, &iph->daddr),
530 IP_VS_DBG_ADDR(svc->af, &dest->addr), ntohs(dest->port));
537 * IPVS LBLC Scheduler structure
539 static struct ip_vs_scheduler ip_vs_lblc_scheduler =
542 .refcnt = ATOMIC_INIT(0),
543 .module = THIS_MODULE,
544 .n_list = LIST_HEAD_INIT(ip_vs_lblc_scheduler.n_list),
545 .init_service = ip_vs_lblc_init_svc,
546 .done_service = ip_vs_lblc_done_svc,
547 .schedule = ip_vs_lblc_schedule,
554 static int __net_init __ip_vs_lblc_init(struct net *net)
556 struct netns_ipvs *ipvs = net_ipvs(net);
561 if (!net_eq(net, &init_net)) {
562 ipvs->lblc_ctl_table = kmemdup(vs_vars_table,
563 sizeof(vs_vars_table),
565 if (ipvs->lblc_ctl_table == NULL)
568 /* Don't export sysctls to unprivileged users */
569 if (net->user_ns != &init_user_ns)
570 ipvs->lblc_ctl_table[0].procname = NULL;
573 ipvs->lblc_ctl_table = vs_vars_table;
574 ipvs->sysctl_lblc_expiration = DEFAULT_EXPIRATION;
575 ipvs->lblc_ctl_table[0].data = &ipvs->sysctl_lblc_expiration;
577 ipvs->lblc_ctl_header =
578 register_net_sysctl(net, "net/ipv4/vs", ipvs->lblc_ctl_table);
579 if (!ipvs->lblc_ctl_header) {
580 if (!net_eq(net, &init_net))
581 kfree(ipvs->lblc_ctl_table);
588 static void __net_exit __ip_vs_lblc_exit(struct net *net)
590 struct netns_ipvs *ipvs = net_ipvs(net);
592 unregister_net_sysctl_table(ipvs->lblc_ctl_header);
594 if (!net_eq(net, &init_net))
595 kfree(ipvs->lblc_ctl_table);
600 static int __net_init __ip_vs_lblc_init(struct net *net) { return 0; }
601 static void __net_exit __ip_vs_lblc_exit(struct net *net) { }
605 static struct pernet_operations ip_vs_lblc_ops = {
606 .init = __ip_vs_lblc_init,
607 .exit = __ip_vs_lblc_exit,
610 static int __init ip_vs_lblc_init(void)
614 ret = register_pernet_subsys(&ip_vs_lblc_ops);
618 ret = register_ip_vs_scheduler(&ip_vs_lblc_scheduler);
620 unregister_pernet_subsys(&ip_vs_lblc_ops);
624 static void __exit ip_vs_lblc_cleanup(void)
626 unregister_ip_vs_scheduler(&ip_vs_lblc_scheduler);
627 unregister_pernet_subsys(&ip_vs_lblc_ops);
632 module_init(ip_vs_lblc_init);
633 module_exit(ip_vs_lblc_cleanup);
634 MODULE_LICENSE("GPL");