1 files changed, 163 insertions, 0 deletions

diff --git a/net/ipv4/ipvs/ip_vs_sed.c b/net/ipv4/ipvs/ip_vs_sed.c
new file mode 100644
index 000000000000..ff366f7390d9
--- /dev/null
+++ b/net/ipv4/ipvs/ip_vs_sed.c
@@ -0,0 +1,163 @@
+/*
+ * IPVS:        Shortest Expected Delay scheduling module
+ *
+ * Version:     $Id: ip_vs_sed.c,v 1.1 2003/05/10 03:06:08 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/module.h>
+#include <linux/kernel.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, const struct sk_buff *skb)
+{
+        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.
+         */
+
+        list_for_each_entry(dest, &svc->destinations, n_list) {
+                if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
+                    atomic_read(&dest->weight) > 0) {
+                        least = dest;
+                        loh = ip_vs_sed_dest_overhead(least);
+                        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 = 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");