/* * IPVS:        Never Queue scheduling module * * Version:     $Id: ip_vs_nq.c,v 1.2 2003/06/08 09:31:19 wensong Exp $ * * 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 intip_vs_nq_init_svc(struct ip_vs_service *svc){	return 0;}static intip_vs_nq_done_svc(struct ip_vs_service *svc){	return 0;}static intip_vs_nq_update_svc(struct ip_vs_service *svc){	return 0;}static inline unsigned intip_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");