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 uninitilized 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.
43 #include <linux/module.h>
44 #include <linux/kernel.h>
45 #include <linux/skbuff.h>
46 #include <linux/jiffies.h>
50 #include <linux/sysctl.h>
52 #include <net/ip_vs.h>
56 * It is for garbage collection of stale IPVS lblc entries,
57 * when the table is full.
59 #define CHECK_EXPIRE_INTERVAL (60*HZ)
60 #define ENTRY_TIMEOUT (6*60*HZ)
63 * It is for full expiration check.
64 * When there is no partial expiration check (garbage collection)
65 * in a half hour, do a full expiration check to collect stale
66 * entries that haven't been touched for a day.
68 #define COUNT_FOR_FULL_EXPIRATION 30
69 static int sysctl_ip_vs_lblc_expiration
= 24*60*60*HZ
;
73 * for IPVS lblc entry hash table
75 #ifndef CONFIG_IP_VS_LBLC_TAB_BITS
76 #define CONFIG_IP_VS_LBLC_TAB_BITS 10
78 #define IP_VS_LBLC_TAB_BITS CONFIG_IP_VS_LBLC_TAB_BITS
79 #define IP_VS_LBLC_TAB_SIZE (1 << IP_VS_LBLC_TAB_BITS)
80 #define IP_VS_LBLC_TAB_MASK (IP_VS_LBLC_TAB_SIZE - 1)
84 * IPVS lblc entry represents an association between destination
85 * IP address and its destination server
87 struct ip_vs_lblc_entry
{
88 struct list_head list
;
89 int af
; /* address family */
90 union nf_inet_addr addr
; /* destination IP address */
91 struct ip_vs_dest
*dest
; /* real server (cache) */
92 unsigned long lastuse
; /* last used time */
97 * IPVS lblc hash table
99 struct ip_vs_lblc_table
{
100 struct list_head bucket
[IP_VS_LBLC_TAB_SIZE
]; /* hash bucket */
101 atomic_t entries
; /* number of entries */
102 int max_size
; /* maximum size of entries */
103 struct timer_list periodic_timer
; /* collect stale entries */
104 int rover
; /* rover for expire check */
105 int counter
; /* counter for no expire */
110 * IPVS LBLC sysctl table
113 static ctl_table vs_vars_table
[] = {
115 .procname
= "lblc_expiration",
116 .data
= &sysctl_ip_vs_lblc_expiration
,
117 .maxlen
= sizeof(int),
119 .proc_handler
= proc_dointvec_jiffies
,
124 static struct ctl_table_header
* sysctl_header
;
126 static inline void ip_vs_lblc_free(struct ip_vs_lblc_entry
*en
)
130 * We don't kfree dest because it is refered either by its service
131 * or the trash dest list.
133 atomic_dec(&en
->dest
->refcnt
);
139 * Returns hash value for IPVS LBLC entry
141 static inline unsigned
142 ip_vs_lblc_hashkey(int af
, const union nf_inet_addr
*addr
)
144 __be32 addr_fold
= addr
->ip
;
146 #ifdef CONFIG_IP_VS_IPV6
148 addr_fold
= addr
->ip6
[0]^addr
->ip6
[1]^
149 addr
->ip6
[2]^addr
->ip6
[3];
151 return (ntohl(addr_fold
)*2654435761UL) & IP_VS_LBLC_TAB_MASK
;
156 * Hash an entry in the ip_vs_lblc_table.
157 * returns bool success.
160 ip_vs_lblc_hash(struct ip_vs_lblc_table
*tbl
, struct ip_vs_lblc_entry
*en
)
162 unsigned hash
= ip_vs_lblc_hashkey(en
->af
, &en
->addr
);
164 list_add(&en
->list
, &tbl
->bucket
[hash
]);
165 atomic_inc(&tbl
->entries
);
170 * Get ip_vs_lblc_entry associated with supplied parameters. Called under read
173 static inline struct ip_vs_lblc_entry
*
174 ip_vs_lblc_get(int af
, struct ip_vs_lblc_table
*tbl
,
175 const union nf_inet_addr
*addr
)
177 unsigned hash
= ip_vs_lblc_hashkey(af
, addr
);
178 struct ip_vs_lblc_entry
*en
;
180 list_for_each_entry(en
, &tbl
->bucket
[hash
], list
)
181 if (ip_vs_addr_equal(af
, &en
->addr
, addr
))
189 * Create or update an ip_vs_lblc_entry, which is a mapping of a destination IP
190 * address to a server. Called under write lock.
192 static inline struct ip_vs_lblc_entry
*
193 ip_vs_lblc_new(struct ip_vs_lblc_table
*tbl
, const union nf_inet_addr
*daddr
,
194 struct ip_vs_dest
*dest
)
196 struct ip_vs_lblc_entry
*en
;
198 en
= ip_vs_lblc_get(dest
->af
, tbl
, daddr
);
200 en
= kmalloc(sizeof(*en
), GFP_ATOMIC
);
202 IP_VS_ERR("ip_vs_lblc_new(): no memory\n");
207 ip_vs_addr_copy(dest
->af
, &en
->addr
, daddr
);
208 en
->lastuse
= jiffies
;
210 atomic_inc(&dest
->refcnt
);
213 ip_vs_lblc_hash(tbl
, en
);
214 } else if (en
->dest
!= dest
) {
215 atomic_dec(&en
->dest
->refcnt
);
216 atomic_inc(&dest
->refcnt
);
225 * Flush all the entries of the specified table.
227 static void ip_vs_lblc_flush(struct ip_vs_lblc_table
*tbl
)
229 struct ip_vs_lblc_entry
*en
, *nxt
;
232 for (i
=0; i
<IP_VS_LBLC_TAB_SIZE
; i
++) {
233 list_for_each_entry_safe(en
, nxt
, &tbl
->bucket
[i
], list
) {
235 atomic_dec(&tbl
->entries
);
241 static inline void ip_vs_lblc_full_check(struct ip_vs_service
*svc
)
243 struct ip_vs_lblc_table
*tbl
= svc
->sched_data
;
244 struct ip_vs_lblc_entry
*en
, *nxt
;
245 unsigned long now
= jiffies
;
248 for (i
=0, j
=tbl
->rover
; i
<IP_VS_LBLC_TAB_SIZE
; i
++) {
249 j
= (j
+ 1) & IP_VS_LBLC_TAB_MASK
;
251 write_lock(&svc
->sched_lock
);
252 list_for_each_entry_safe(en
, nxt
, &tbl
->bucket
[j
], list
) {
254 en
->lastuse
+ sysctl_ip_vs_lblc_expiration
))
258 atomic_dec(&tbl
->entries
);
260 write_unlock(&svc
->sched_lock
);
267 * Periodical timer handler for IPVS lblc table
268 * It is used to collect stale entries when the number of entries
269 * exceeds the maximum size of the table.
271 * Fixme: we probably need more complicated algorithm to collect
272 * entries that have not been used for a long time even
273 * if the number of entries doesn't exceed the maximum size
275 * The full expiration check is for this purpose now.
277 static void ip_vs_lblc_check_expire(unsigned long data
)
279 struct ip_vs_service
*svc
= (struct ip_vs_service
*) data
;
280 struct ip_vs_lblc_table
*tbl
= svc
->sched_data
;
281 unsigned long now
= jiffies
;
284 struct ip_vs_lblc_entry
*en
, *nxt
;
286 if ((tbl
->counter
% COUNT_FOR_FULL_EXPIRATION
) == 0) {
287 /* do full expiration check */
288 ip_vs_lblc_full_check(svc
);
293 if (atomic_read(&tbl
->entries
) <= tbl
->max_size
) {
298 goal
= (atomic_read(&tbl
->entries
) - tbl
->max_size
)*4/3;
299 if (goal
> tbl
->max_size
/2)
300 goal
= tbl
->max_size
/2;
302 for (i
=0, j
=tbl
->rover
; i
<IP_VS_LBLC_TAB_SIZE
; i
++) {
303 j
= (j
+ 1) & IP_VS_LBLC_TAB_MASK
;
305 write_lock(&svc
->sched_lock
);
306 list_for_each_entry_safe(en
, nxt
, &tbl
->bucket
[j
], list
) {
307 if (time_before(now
, en
->lastuse
+ ENTRY_TIMEOUT
))
311 atomic_dec(&tbl
->entries
);
314 write_unlock(&svc
->sched_lock
);
321 mod_timer(&tbl
->periodic_timer
, jiffies
+CHECK_EXPIRE_INTERVAL
);
325 static int ip_vs_lblc_init_svc(struct ip_vs_service
*svc
)
328 struct ip_vs_lblc_table
*tbl
;
331 * Allocate the ip_vs_lblc_table for this service
333 tbl
= kmalloc(sizeof(*tbl
), GFP_ATOMIC
);
335 IP_VS_ERR("ip_vs_lblc_init_svc(): no memory\n");
338 svc
->sched_data
= tbl
;
339 IP_VS_DBG(6, "LBLC hash table (memory=%Zdbytes) allocated for "
340 "current service\n", sizeof(*tbl
));
343 * Initialize the hash buckets
345 for (i
=0; i
<IP_VS_LBLC_TAB_SIZE
; i
++) {
346 INIT_LIST_HEAD(&tbl
->bucket
[i
]);
348 tbl
->max_size
= IP_VS_LBLC_TAB_SIZE
*16;
353 * Hook periodic timer for garbage collection
355 setup_timer(&tbl
->periodic_timer
, ip_vs_lblc_check_expire
,
357 mod_timer(&tbl
->periodic_timer
, jiffies
+ CHECK_EXPIRE_INTERVAL
);
363 static int ip_vs_lblc_done_svc(struct ip_vs_service
*svc
)
365 struct ip_vs_lblc_table
*tbl
= svc
->sched_data
;
367 /* remove periodic timer */
368 del_timer_sync(&tbl
->periodic_timer
);
370 /* got to clean up table entries here */
371 ip_vs_lblc_flush(tbl
);
373 /* release the table itself */
375 IP_VS_DBG(6, "LBLC hash table (memory=%Zdbytes) released\n",
382 static inline struct ip_vs_dest
*
383 __ip_vs_lblc_schedule(struct ip_vs_service
*svc
)
385 struct ip_vs_dest
*dest
, *least
;
389 * We think the overhead of processing active connections is fifty
390 * times higher than that of inactive connections in average. (This
391 * fifty times might not be accurate, we will change it later.) We
392 * use the following formula to estimate the overhead:
393 * dest->activeconns*50 + dest->inactconns
395 * (dest overhead) / dest->weight
397 * Remember -- no floats in kernel mode!!!
398 * The comparison of h1*w2 > h2*w1 is equivalent to that of
400 * if every weight is larger than zero.
402 * The server with weight=0 is quiesced and will not receive any
405 list_for_each_entry(dest
, &svc
->destinations
, n_list
) {
406 if (dest
->flags
& IP_VS_DEST_F_OVERLOAD
)
408 if (atomic_read(&dest
->weight
) > 0) {
410 loh
= atomic_read(&least
->activeconns
) * 50
411 + atomic_read(&least
->inactconns
);
418 * Find the destination with the least load.
421 list_for_each_entry_continue(dest
, &svc
->destinations
, n_list
) {
422 if (dest
->flags
& IP_VS_DEST_F_OVERLOAD
)
425 doh
= atomic_read(&dest
->activeconns
) * 50
426 + atomic_read(&dest
->inactconns
);
427 if (loh
* atomic_read(&dest
->weight
) >
428 doh
* atomic_read(&least
->weight
)) {
434 IP_VS_DBG_BUF(6, "LBLC: server %s:%d "
435 "activeconns %d refcnt %d weight %d overhead %d\n",
436 IP_VS_DBG_ADDR(least
->af
, &least
->addr
),
438 atomic_read(&least
->activeconns
),
439 atomic_read(&least
->refcnt
),
440 atomic_read(&least
->weight
), loh
);
447 * If this destination server is overloaded and there is a less loaded
448 * server, then return true.
451 is_overloaded(struct ip_vs_dest
*dest
, struct ip_vs_service
*svc
)
453 if (atomic_read(&dest
->activeconns
) > atomic_read(&dest
->weight
)) {
454 struct ip_vs_dest
*d
;
456 list_for_each_entry(d
, &svc
->destinations
, n_list
) {
457 if (atomic_read(&d
->activeconns
)*2
458 < atomic_read(&d
->weight
)) {
468 * Locality-Based (weighted) Least-Connection scheduling
470 static struct ip_vs_dest
*
471 ip_vs_lblc_schedule(struct ip_vs_service
*svc
, const struct sk_buff
*skb
)
473 struct ip_vs_lblc_table
*tbl
= svc
->sched_data
;
474 struct ip_vs_iphdr iph
;
475 struct ip_vs_dest
*dest
= NULL
;
476 struct ip_vs_lblc_entry
*en
;
478 ip_vs_fill_iphdr(svc
->af
, skb_network_header(skb
), &iph
);
480 IP_VS_DBG(6, "ip_vs_lblc_schedule(): Scheduling...\n");
482 /* First look in our cache */
483 read_lock(&svc
->sched_lock
);
484 en
= ip_vs_lblc_get(svc
->af
, tbl
, &iph
.daddr
);
486 /* We only hold a read lock, but this is atomic */
487 en
->lastuse
= jiffies
;
490 * If the destination is not available, i.e. it's in the trash,
491 * we must ignore it, as it may be removed from under our feet,
492 * if someone drops our reference count. Our caller only makes
493 * sure that destinations, that are not in the trash, are not
494 * moved to the trash, while we are scheduling. But anyone can
495 * free up entries from the trash at any time.
498 if (en
->dest
->flags
& IP_VS_DEST_F_AVAILABLE
)
501 read_unlock(&svc
->sched_lock
);
503 /* If the destination has a weight and is not overloaded, use it */
504 if (dest
&& atomic_read(&dest
->weight
) > 0 && !is_overloaded(dest
, svc
))
507 /* No cache entry or it is invalid, time to schedule */
508 dest
= __ip_vs_lblc_schedule(svc
);
510 IP_VS_DBG(1, "no destination available\n");
514 /* If we fail to create a cache entry, we'll just use the valid dest */
515 write_lock(&svc
->sched_lock
);
516 ip_vs_lblc_new(tbl
, &iph
.daddr
, dest
);
517 write_unlock(&svc
->sched_lock
);
520 IP_VS_DBG_BUF(6, "LBLC: destination IP address %s --> server %s:%d\n",
521 IP_VS_DBG_ADDR(svc
->af
, &iph
.daddr
),
522 IP_VS_DBG_ADDR(svc
->af
, &dest
->addr
), ntohs(dest
->port
));
529 * IPVS LBLC Scheduler structure
531 static struct ip_vs_scheduler ip_vs_lblc_scheduler
=
534 .refcnt
= ATOMIC_INIT(0),
535 .module
= THIS_MODULE
,
536 .n_list
= LIST_HEAD_INIT(ip_vs_lblc_scheduler
.n_list
),
537 .init_service
= ip_vs_lblc_init_svc
,
538 .done_service
= ip_vs_lblc_done_svc
,
539 .schedule
= ip_vs_lblc_schedule
,
543 static int __init
ip_vs_lblc_init(void)
547 sysctl_header
= register_sysctl_paths(net_vs_ctl_path
, vs_vars_table
);
548 ret
= register_ip_vs_scheduler(&ip_vs_lblc_scheduler
);
550 unregister_sysctl_table(sysctl_header
);
555 static void __exit
ip_vs_lblc_cleanup(void)
557 unregister_sysctl_table(sysctl_header
);
558 unregister_ip_vs_scheduler(&ip_vs_lblc_scheduler
);
562 module_init(ip_vs_lblc_init
);
563 module_exit(ip_vs_lblc_cleanup
);
564 MODULE_LICENSE("GPL");