patch-2.4.23 linux-2.4.23/net/ipv4/ipvs/ip_vs_sed.c

• Lines: 168
• Date: 2003-11-28 10:26:21.000000000 -0800
• Orig file: linux-2.4.22/net/ipv4/ipvs/ip_vs_sed.c
• Orig date: 1969-12-31 16:00:00.000000000 -0800

diff -urN linux-2.4.22/net/ipv4/ipvs/ip_vs_sed.c linux-2.4.23/net/ipv4/ipvs/ip_vs_sed.c
@@ -0,0 +1,167 @@
+/*
+ * IPVS:        Shortest Expected Delay scheduling module
+ *
+ * Version:     $Id: ip_vs_sed.c,v 1.1.2.1 2003/05/20 17:05:02 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 SED algorithm attempts to minimize each job's expected delay until
+ * completion. The expected delay that the job will experience is
+ * (Ci + 1) / Ui if sent to the ith server, in which Ci is the number of
+ * jobs on the the ith server and Ui is the fixed service rate (weight) of
+ * the ith server. The SED algorithm adopts a greedy policy that each does
+ * what is in its own best interest, i.e. to join the queue which would
+ * minimize its expected delay of completion.
+ *
+ * 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 SED to me.
+ *
+ * The difference between SED and WLC is that SED includes the incoming
+ * job in the cost function (the increment of 1). SED may outperform
+ * WLC, while scheduling big jobs under larger heterogeneous systems
+ * (the server weight varies a lot).
+ *
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+
+#include <net/ip_vs.h>
+
+
+static int
+ip_vs_sed_init_svc(struct ip_vs_service *svc)
+{
+	return 0;
+}
+
+
+static int
+ip_vs_sed_done_svc(struct ip_vs_service *svc)
+{
+	return 0;
+}
+
+
+static int
+ip_vs_sed_update_svc(struct ip_vs_service *svc)
+{
+	return 0;
+}
+
+
+static inline unsigned int
+ip_vs_sed_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_sed_schedule(struct ip_vs_service *svc, struct iphdr *iph)
+{
+	register struct list_head *l, *e;
+	struct ip_vs_dest *dest, *least;
+	unsigned int loh, doh;
+
+	IP_VS_DBG(6, "ip_vs_sed_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.
+	 */
+
+	l = &svc->destinations;
+	for (e=l->next; e!=l; e=e->next) {
+		least = list_entry(e, struct ip_vs_dest, n_list);
+		if (atomic_read(&least->weight) > 0) {
+			loh = ip_vs_sed_dest_overhead(least);
+			goto nextstage;
+		}
+	}
+	return NULL;
+
+	/*
+	 *    Find the destination with the least load.
+	 */
+  nextstage:
+	for (e=e->next; e!=l; e=e->next) {
+		dest = list_entry(e, struct ip_vs_dest, n_list);
+		doh = ip_vs_sed_dest_overhead(dest);
+		if (loh * atomic_read(&dest->weight) >
+		    doh * atomic_read(&least->weight)) {
+			least = dest;
+			loh = doh;
+		}
+	}
+
+	IP_VS_DBG(6, "SED: 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_sed_scheduler =
+{
+	.name =			"sed",
+	.refcnt =		ATOMIC_INIT(0),
+	.module =		THIS_MODULE,
+	.init_service =		ip_vs_sed_init_svc,
+	.done_service =		ip_vs_sed_done_svc,
+	.update_service =	ip_vs_sed_update_svc,
+	.schedule =		ip_vs_sed_schedule,
+};
+
+
+static int __init ip_vs_sed_init(void)
+{
+	INIT_LIST_HEAD(&ip_vs_sed_scheduler.n_list);
+	return register_ip_vs_scheduler(&ip_vs_sed_scheduler);
+}
+
+static void __exit ip_vs_sed_cleanup(void)
+{
+	unregister_ip_vs_scheduler(&ip_vs_sed_scheduler);
+}
+
+module_init(ip_vs_sed_init);
+module_exit(ip_vs_sed_cleanup);
+MODULE_LICENSE("GPL");