/*
* IPVS: Locality-Based Least-Connection scheduling module
*
* Authors: Wensong Zhang <wensong@gnuchina.org>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Changes:
* Martin Hamilton : fixed the terrible locking bugs
* *lock(tbl->lock) ==> *lock(&tbl->lock)
* Wensong Zhang : fixed the uninitilized tbl->lock bug
* Wensong Zhang : added doing full expiration check to
* collect stale entries of 24+ hours when
* no partial expire check in a half hour
* Julian Anastasov : replaced del_timer call with del_timer_sync
* to avoid the possible race between timer
* handler and del_timer thread in SMP
*
*/
/*
* The lblc algorithm is as follows (pseudo code):
*
* if cachenode[dest_ip] is null then
* n, cachenode[dest_ip] <- {weighted least-conn node};
* else
* n <- cachenode[dest_ip];
* if (n is dead) OR
* (n.conns>n.weight AND
* there is a node m with m.conns<m.weight/2) then
* n, cachenode[dest_ip] <- {weighted least-conn node};
*
* return n;
*
* Thanks must go to Wenzhuo Zhang for talking WCCP to me and pushing
* me to write this module.
*/
#include <linux/ip.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/jiffies.h>
/* for sysctl */
#include <linux/fs.h>
#include <linux/sysctl.h>
#include <net/ip_vs.h>
/*
* It is for garbage collection of stale IPVS lblc entries,
* when the table is full.
*/
#define CHECK_EXPIRE_INTERVAL (60*HZ)
#define ENTRY_TIMEOUT (6*60*HZ)
/*
* It is for full expiration check.
* When there is no partial expiration check (garbage collection)
* in a half hour, do a full expiration check to collect stale
* entries that haven't been touched for a day.
*/
#define COUNT_FOR_FULL_EXPIRATION 30
static int sysctl_ip_vs_lblc_expiration = 24*60*60*HZ;
/*
* for IPVS lblc entry hash table
*/
#ifndef CONFIG_IP_VS_LBLC_TAB_BITS
#define CONFIG_IP_VS_LBLC_TAB_BITS 10
#endif
#define IP_VS_LBLC_TAB_BITS CONFIG_IP_VS_LBLC_TAB_BITS
#define IP_VS_LBLC_TAB_SIZE (1 << IP_VS_LBLC_TAB_BITS)
#define IP_VS_LBLC_TAB_MASK (IP_VS_LBLC_TAB_SIZE - 1)
/*
* IPVS lblc entry represents an association between destination
* IP address and its destination server
*/
struct ip_vs_lblc_entry {
struct list_head list;
__be32 addr; /* destination IP address */
struct ip_vs_dest *dest; /* real server (cache) */
unsigned long lastuse; /* last used time */
};
/*
* IPVS lblc hash table
*/
struct ip_vs_lblc_table {
rwlock_t lock; /* lock for this table */
struct list_head bucket[IP_VS_LBLC_TAB_SIZE]; /* hash bucket */
atomic_t entries; /* number of entries */
int max_size; /* maximum size of entries */
struct timer_list periodic_timer; /* collect stale entries */
int rover; /* rover for expire check */
int counter; /* counter for no expire */
};
/*
* IPVS LBLC sysctl table
*/
static ctl_table vs_vars_table[] = {
{
.procname = "lblc_expiration",
.data = &sysctl_ip_vs_lblc_expiration,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &proc_dointvec_jiffies,
},
{ .ctl_name = 0 }
};
static struct ctl_table_header * sysctl_header;
/*
* new/free a ip_vs_lblc_entry, which is a mapping of a destionation
* IP address to a server.
*/
static inline struct ip_vs_lblc_entry *
ip_vs_lblc_new(__be32 daddr, struct ip_vs_dest *dest)
{
struct ip_vs_lblc_entry *en;
en = kmalloc(sizeof(struct ip_vs_lblc_entry), GFP_ATOMIC);
if (en == NULL) {
IP_VS_ERR("ip_vs_lblc_new(): no memory\n");
return NULL;
}
INIT_LIST_HEAD(&en->list);
en->addr = daddr;
atomic_inc(&dest->refcnt);
en->dest = dest;
return en;
}
static inline void ip_vs_lblc_free(struct ip_vs_lblc_entry *en)
{
list_del(&en->list);
/*
* We don't kfree dest because it is refered either by its service
* or the trash dest list.
*/
atomic_dec(&en->dest->refcnt);
kfree(en);
}
/*
* Returns hash value for IPVS LBLC entry
*/
static inline unsigned ip_vs_lblc_hashkey(__be32 addr)
{
return (ntohl(addr)*2654435761UL) & IP_VS_LBLC_TAB_MASK;
}
/*
* Hash an entry in the ip_vs_lblc_table.
* returns bool success.
*/
static int
ip_vs_lblc_hash(struct ip_vs_lblc_table *tbl, struct ip_vs_lblc_entry *en)
{
unsigned hash;
if (!list_empty(&en->list)) {
IP_VS_ERR("ip_vs_lblc_hash(): request for already hashed, "
"called from %p\n", __builtin_return_address(0));
return 0;
}
/*
* Hash by destination IP address
*/
hash = ip_vs_lblc_hashkey(en->addr);
write_lock(&tbl->lock);
list_add(&en->list, &tbl->bucket[hash]);
atomic_inc(&tbl->entries);
write_unlock(&tbl->lock);
return 1;
}
/*
* Get ip_vs_lblc_entry associated with supplied parameters.
*/
static inline struct ip_vs_lblc_entry *
ip_vs_lblc_get(struct ip_vs_lblc_table *tbl, __be32 addr)
{
unsigned hash;
struct ip_vs_lblc_entry *en;
hash = ip_vs_lblc_hashkey(addr);
read_lock(&tbl->lock);
list_for_each_entry(en, &tbl->bucket[hash], list) {
if (en->addr == addr) {
/* HIT */
read_unlock(&tbl->lock);
return en;
}
}
read_unlock(&tbl->lock);
return NULL;
}
/*
* Flush all the entries of the specified table.
*/
static void ip_vs_lblc_flush(struct ip_vs_lblc_table *tbl)
{
int i;
struct ip_vs_lblc_entry *en, *nxt;
for (i=0; i<IP_VS_LBLC_TAB_SIZE; i++) {
write_lock(&tbl->lock);
list_for_each_entry_safe(en, nxt, &tbl->bucket[i], list) {
ip_vs_lblc_free(en);
atomic_dec(&tbl->entries);
}
write_unlock(&tbl->lock);
}
}
static inline void ip_vs_lblc_full_check(struct ip_vs_lblc_table *tbl)
{
unsigned long now = jiffies;
int i, j;
struct ip_vs_lblc_entry *en, *nxt;
for (i=0, j=tbl->rover; i<IP_VS_LBLC_TAB_SIZE; i++) {
j = (j + 1) & IP_VS_LBLC_TAB_MASK;
write_lock(&tbl->lock);
list_for_each_entry_safe(en, nxt, &tbl->bucket[j], list) {
if (time_before(now,
en->lastuse + sysctl_ip_vs_lblc_expiration))
continue;
ip_vs_lblc_free(en);
atomic_dec(&tbl->entries);
}
write_unlock(&tbl->lock);
}
tbl->rover = j;
}
/*
* Periodical timer handler for IPVS lblc table
* It is used to collect stale entries when the number of entries
* exceeds the maximum size of the table.
*
* Fixme: we probably need more complicated algorithm to collect
* entries that have not been used for a long time even
* if the number of entries doesn't exceed the maximum size
* of the table.
* The full expiration check is for this purpose now.
*/
static void ip_vs_lblc_check_expire(unsigned long data)
{
struct ip_vs_lblc_table *tbl;
unsigned long now = jiffies;
int goal;
int i, j;
struct ip_vs_lblc_entry *en, *nxt;
tbl = (struct ip_vs_lblc_table *)data;
if ((tbl->counter % COUNT_FOR_FULL_EXPIRATION) == 0) {
/* do full expiration check */
ip_vs_lblc_full_check(tbl);
tbl->counter = 1;
goto out;
}
if (atomic_read(&tbl->entries) <= tbl->max_size) {
tbl->counter++;
goto out;
}
goal = (atomic_read(&tbl->entries) - tbl->max_size)*4/3;
if (goal > tbl->max_size/2)
goal = tbl->max_size/2;
for (i=0, j=tbl->rover; i<IP_VS_LBLC_TAB_SIZE; i++) {
j = (j + 1) & IP_VS_LBLC_TAB_MASK;
write_lock(&tbl->lock);
list_for_each_entry_safe(en, nxt, &tbl->bucket[j], list) {
if (time_before(now, en->lastuse + ENTRY_TIMEOUT))
continue;
ip_vs_lblc_free(en);
atomic_dec(&tbl->entries);
goal--;
}
write_unlock(&tbl->lock);
if (goal <= 0)
break;
}
tbl->rover = j;
out:
mod_timer(&tbl->periodic_timer, jiffies+CHECK_EXPIRE_INTERVAL);
}
static int ip_vs_lblc_init_svc(struct ip_vs_service *svc)
{
int i;
struct ip_vs_lblc_table *tbl;
/*
* Allocate the ip_vs_lblc_table for this service
*/
tbl = kmalloc(sizeof(struct ip_vs_lblc_table), GFP_ATOMIC);
if (tbl == NULL) {
IP_VS_ERR("ip_vs_lblc_init_svc(): no memory\n");
return -ENOMEM;
}
svc->sched_data = tbl;
IP_VS_DBG(6, "LBLC hash table (memory=%Zdbytes) allocated for "
"current service\n",
sizeof(struct ip_vs_lblc_table));
/*
* Initialize the hash buckets
*/
for (i=0; i<IP_VS_LBLC_TAB_SIZE; i++) {
INIT_LIST_HEAD(&tbl->bucket[i]);
}
rwlock_init(&tbl->lock);
tbl->max_size = IP_VS_LBLC_TAB_SIZE*16;
tbl->rover = 0;
tbl->counter = 1;
/*
* Hook periodic timer for garbage collection
*/
setup_timer(&tbl->periodic_timer, ip_vs_lblc_check_expire,
(unsigned long)tbl);
tbl->periodic_timer.expires = jiffies+CHECK_EXPIRE_INTERVAL;
add_timer(&tbl->periodic_timer);
return 0;
}
static int ip_vs_lblc_done_svc(struct ip_vs_service *svc)
{
struct ip_vs_lblc_table *tbl = svc->sched_data;
/* remove periodic timer */
del_timer_sync(&tbl->periodic_timer);
/* got to clean up table entries here */
ip_vs_lblc_flush(tbl);
/* release the table itself */
kfree(svc->sched_data);
IP_VS_DBG(6, "LBLC hash table (memory=%Zdbytes) released\n",
sizeof(struct ip_vs_lblc_table));
return 0;
}
static int ip_vs_lblc_update_svc(struct ip_vs_service *svc)
{
return 0;
}
static inline struct ip_vs_dest *
__ip_vs_wlc_schedule(struct ip_vs_service *svc, struct iphdr *iph)
{
struct ip_vs_dest *dest, *least;
int loh, doh;
/*
* We think the overhead of processing active connections is fifty
* times higher than that of inactive connections in average. (This
* fifty times might not be accurate, we will change it later.) We
* use the following formula to estimate the overhead:
* dest->activeconns*50 + dest->inactconns
* and the load:
* (dest overhead) / dest->weight
*
* Remember -- no floats in kernel mode!!!
* The comparison of h1*w2 > h2*w1 is equivalent to that of
* h1/w1 > h2/w2
* if every weight is larger than zero.
*
* The server with weight=0 is quiesced and will not receive any
* new connection.
*/
list_for_each_entry(dest, &svc->destinations, n_list) {
if (dest->flags & IP_VS_DEST_F_OVERLOAD)
continue;
if (atomic_read(&dest->weight) > 0) {
least = dest;
loh = atomic_read(&least->activeconns) * 50
+ atomic_read(&least->inactconns);
goto nextstage;
}
}
return NULL;
/*
* Find the destination with the least load.
*/
nextstage:
list_for_each_entry_continue(dest, &svc->destinations, n_list) {
if (dest->flags & IP_VS_DEST_F_OVERLOAD)
continue;
doh = atomic_read(&dest->activeconns) * 50
+ atomic_read(&dest->inactconns);
if (loh * atomic_read(&dest->weight) >
doh * atomic_read(&least->weight)) {
least = dest;
loh = doh;
}
}
IP_VS_DBG(6, "LBLC: server %d.%d.%d.%d:%d "
"activeconns %d refcnt %d weight %d overhead %d\n",
NIPQUAD(least->addr), ntohs(least->port),
atomic_read(&least->activeconns),
atomic_read(&least->refcnt),
atomic_read(&least->weight), loh);
return least;
}
/*
* If this destination server is overloaded and there is a less loaded
* server, then return true.
*/
static inline int
is_overloaded(struct ip_vs_dest *dest, struct ip_vs_service *svc)
{
if (atomic_read(&dest->activeconns) > atomic_read(&dest->weight)) {
struct ip_vs_dest *d;
list_for_each_entry(d, &svc->destinations, n_list) {
if (atomic_read(&d->activeconns)*2
< atomic_read(&d->weight)) {
return 1;
}
}
}
return 0;
}
/*
* Locality-Based (weighted) Least-Connection scheduling
*/
static struct ip_vs_dest *
ip_vs_lblc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
{
struct ip_vs_dest *dest;
struct ip_vs_lblc_table *tbl;
struct ip_vs_lblc_entry *en;
struct iphdr *iph = ip_hdr(skb);
IP_VS_DBG(6, "ip_vs_lblc_schedule(): Scheduling...\n");
tbl = (struct ip_vs_lblc_table *)svc->sched_data;
en = ip_vs_lblc_get(tbl, iph->daddr);
if (en == NULL) {
dest = __ip_vs_wlc_schedule(svc, iph);
if (dest == NULL) {
IP_VS_DBG(1, "no destination available\n");
return NULL;
}
en = ip_vs_lblc_new(iph->daddr, dest);
if (en == NULL) {
return NULL;
}
ip_vs_lblc_hash(tbl, en);
} else {
dest = en->dest;
if (!(dest->flags & IP_VS_DEST_F_AVAILABLE)
|| atomic_read(&dest->weight) <= 0
|| is_overloaded(dest, svc)) {
dest = __ip_vs_wlc_schedule(svc, iph);
if (dest == NULL) {
IP_VS_DBG(1, "no destination available\n");
return NULL;
}
atomic_dec(&en->dest->refcnt);
atomic_inc(&dest->refcnt);
en->dest = dest;
}
}
en->lastuse = jiffies;
IP_VS_DBG(6, "LBLC: destination IP address %u.%u.%u.%u "
"--> server %u.%u.%u.%u:%d\n",
NIPQUAD(en->addr),
NIPQUAD(dest->addr),
ntohs(dest->port));
return dest;
}
/*
* IPVS LBLC Scheduler structure
*/
static struct ip_vs_scheduler ip_vs_lblc_scheduler =
{
.name = "lblc",
.refcnt = ATOMIC_INIT(0),
.module = THIS_MODULE,
.n_list = LIST_HEAD_INIT(ip_vs_lblc_scheduler.n_list),
.init_service = ip_vs_lblc_init_svc,
.done_service = ip_vs_lblc_done_svc,
.update_service = ip_vs_lblc_update_svc,
.schedule = ip_vs_lblc_schedule,
};
static int __init ip_vs_lblc_init(void)
{
int ret;
sysctl_header = register_sysctl_paths(net_vs_ctl_path, vs_vars_table);
ret = register_ip_vs_scheduler(&ip_vs_lblc_scheduler);
if (ret)
unregister_sysctl_table(sysctl_header);
return ret;
}
static void __exit ip_vs_lblc_cleanup(void)
{
unregister_sysctl_table(sysctl_header);
unregister_ip_vs_scheduler(&ip_vs_lblc_scheduler);
}
module_init(ip_vs_lblc_init);
module_exit(ip_vs_lblc_cleanup);
MODULE_LICENSE("GPL");
