160 lines
3.6 KiB
C
160 lines
3.6 KiB
C
/*
|
|
* IPVS: Never Queue scheduling module
|
|
*
|
|
* Authors: Wensong Zhang <wensong@linuxvirtualserver.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:
|
|
*
|
|
*/
|
|
|
|
/*
|
|
* The NQ algorithm adopts a two-speed model. When there is an idle server
|
|
* available, the job will be sent to the idle server, instead of waiting
|
|
* for a fast one. When there is no idle server available, the job will be
|
|
* sent to the server that minimize its expected delay (The Shortest
|
|
* Expected Delay scheduling algorithm).
|
|
*
|
|
* See the following paper for more information:
|
|
* A. Weinrib and S. Shenker, Greed is not enough: Adaptive load sharing
|
|
* in large heterogeneous systems. In Proceedings IEEE INFOCOM'88,
|
|
* pages 986-994, 1988.
|
|
*
|
|
* Thanks must go to Marko Buuri <marko@buuri.name> for talking NQ to me.
|
|
*
|
|
* The difference between NQ and SED is that NQ can improve overall
|
|
* system utilization.
|
|
*
|
|
*/
|
|
|
|
#include <linux/module.h>
|
|
#include <linux/kernel.h>
|
|
|
|
#include <net/ip_vs.h>
|
|
|
|
|
|
static int
|
|
ip_vs_nq_init_svc(struct ip_vs_service *svc)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
|
|
static int
|
|
ip_vs_nq_done_svc(struct ip_vs_service *svc)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
|
|
static int
|
|
ip_vs_nq_update_svc(struct ip_vs_service *svc)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
|
|
static inline unsigned int
|
|
ip_vs_nq_dest_overhead(struct ip_vs_dest *dest)
|
|
{
|
|
/*
|
|
* We only use the active connection number in the cost
|
|
* calculation here.
|
|
*/
|
|
return atomic_read(&dest->activeconns) + 1;
|
|
}
|
|
|
|
|
|
/*
|
|
* Weighted Least Connection scheduling
|
|
*/
|
|
static struct ip_vs_dest *
|
|
ip_vs_nq_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
|
|
{
|
|
struct ip_vs_dest *dest, *least = NULL;
|
|
unsigned int loh = 0, doh;
|
|
|
|
IP_VS_DBG(6, "ip_vs_nq_schedule(): Scheduling...\n");
|
|
|
|
/*
|
|
* We calculate the load of each dest server as follows:
|
|
* (server expected 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 connections.
|
|
*/
|
|
|
|
list_for_each_entry(dest, &svc->destinations, n_list) {
|
|
|
|
if (dest->flags & IP_VS_DEST_F_OVERLOAD ||
|
|
!atomic_read(&dest->weight))
|
|
continue;
|
|
|
|
doh = ip_vs_nq_dest_overhead(dest);
|
|
|
|
/* return the server directly if it is idle */
|
|
if (atomic_read(&dest->activeconns) == 0) {
|
|
least = dest;
|
|
loh = doh;
|
|
goto out;
|
|
}
|
|
|
|
if (!least ||
|
|
(loh * atomic_read(&dest->weight) >
|
|
doh * atomic_read(&least->weight))) {
|
|
least = dest;
|
|
loh = doh;
|
|
}
|
|
}
|
|
|
|
if (!least)
|
|
return NULL;
|
|
|
|
out:
|
|
IP_VS_DBG(6, "NQ: server %u.%u.%u.%u:%u "
|
|
"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;
|
|
}
|
|
|
|
|
|
static struct ip_vs_scheduler ip_vs_nq_scheduler =
|
|
{
|
|
.name = "nq",
|
|
.refcnt = ATOMIC_INIT(0),
|
|
.module = THIS_MODULE,
|
|
.init_service = ip_vs_nq_init_svc,
|
|
.done_service = ip_vs_nq_done_svc,
|
|
.update_service = ip_vs_nq_update_svc,
|
|
.schedule = ip_vs_nq_schedule,
|
|
};
|
|
|
|
|
|
static int __init ip_vs_nq_init(void)
|
|
{
|
|
INIT_LIST_HEAD(&ip_vs_nq_scheduler.n_list);
|
|
return register_ip_vs_scheduler(&ip_vs_nq_scheduler);
|
|
}
|
|
|
|
static void __exit ip_vs_nq_cleanup(void)
|
|
{
|
|
unregister_ip_vs_scheduler(&ip_vs_nq_scheduler);
|
|
}
|
|
|
|
module_init(ip_vs_nq_init);
|
|
module_exit(ip_vs_nq_cleanup);
|
|
MODULE_LICENSE("GPL");
|