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

• Lines: 266
• Date: 2003-11-28 10:26:21.000000000 -0800
• Orig file: linux-2.4.22/net/ipv4/ipvs/ip_vs_dh.c
• Orig date: 1969-12-31 16:00:00.000000000 -0800

diff -urN linux-2.4.22/net/ipv4/ipvs/ip_vs_dh.c linux-2.4.23/net/ipv4/ipvs/ip_vs_dh.c
@@ -0,0 +1,265 @@
+/*
+ * IPVS:        Destination Hashing scheduling module
+ *
+ * Version:     $Id: ip_vs_dh.c,v 1.4 2001/10/19 15:05:17 wensong Exp $
+ *
+ * Authors:     Wensong Zhang <wensong@gnuchina.org>
+ *
+ *              Inspired by the consistent hashing scheduler patch from
+ *              Thomas Proell <proellt@gmx.de>
+ *
+ *              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 dh algorithm is to select server by the hash key of destination IP
+ * address. The pseudo code is as follows:
+ *
+ *       n <- servernode[dest_ip];
+ *       if (n is dead) OR
+ *          (n is overloaded, such as n.conns>2*n.weight) then
+ *                 return NULL;
+ *
+ *       return n;
+ *
+ * Notes that servernode is a 256-bucket hash table that maps the hash
+ * index derived from packet destination IP address to the current server
+ * array. If the dh scheduler is used in cache cluster, it is good to
+ * combine it with cache_bypass feature. When the statically assigned
+ * server is dead or overloaded, the load balancer can bypass the cache
+ * server and send requests to the original server directly.
+ *
+ */
+
+#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>
+
+
+/*
+ *      IPVS DH bucket
+ */
+struct ip_vs_dh_bucket {
+	struct ip_vs_dest       *dest;          /* real server (cache) */
+};
+
+/*
+ *     for IPVS DH entry hash table
+ */
+#ifndef CONFIG_IP_VS_DH_TAB_BITS
+#define CONFIG_IP_VS_DH_TAB_BITS        8
+#endif
+#define IP_VS_DH_TAB_BITS               CONFIG_IP_VS_DH_TAB_BITS
+#define IP_VS_DH_TAB_SIZE               (1 << IP_VS_DH_TAB_BITS)
+#define IP_VS_DH_TAB_MASK               (IP_VS_DH_TAB_SIZE - 1)
+
+
+/*
+ *	Returns hash value for IPVS DH entry
+ */
+static inline unsigned ip_vs_dh_hashkey(__u32 addr)
+{
+	return (ntohl(addr)*2654435761UL) & IP_VS_DH_TAB_MASK;
+}
+
+
+/*
+ *      Get ip_vs_dest associated with supplied parameters.
+ */
+static inline struct ip_vs_dest *
+ip_vs_dh_get(struct ip_vs_dh_bucket *tbl, __u32 addr)
+{
+	return (tbl[ip_vs_dh_hashkey(addr)]).dest;
+}
+
+
+/*
+ *      Assign all the hash buckets of the specified table with the service.
+ */
+static int
+ip_vs_dh_assign(struct ip_vs_dh_bucket *tbl, struct ip_vs_service *svc)
+{
+	int i;
+	struct ip_vs_dh_bucket *b;
+	struct list_head *p;
+	struct ip_vs_dest *dest;
+
+	b = tbl;
+	p = &svc->destinations;
+	for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {
+		if (list_empty(p)) {
+			b->dest = NULL;
+		} else {
+			if (p == &svc->destinations)
+				p = p->next;
+
+			dest = list_entry(p, struct ip_vs_dest, n_list);
+			atomic_inc(&dest->refcnt);
+			b->dest = dest;
+
+			p = p->next;
+		}
+		b++;
+	}
+	return 0;
+}
+
+
+/*
+ *      Flush all the hash buckets of the specified table.
+ */
+static void ip_vs_dh_flush(struct ip_vs_dh_bucket *tbl)
+{
+	int i;
+	struct ip_vs_dh_bucket *b;
+
+	b = tbl;
+	for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {
+		if (b->dest) {
+			atomic_dec(&b->dest->refcnt);
+			b->dest = NULL;
+		}
+		b++;
+	}
+}
+
+
+static int ip_vs_dh_init_svc(struct ip_vs_service *svc)
+{
+	struct ip_vs_dh_bucket *tbl;
+
+	/* allocate the DH table for this service */
+	tbl = kmalloc(sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE,
+		      GFP_ATOMIC);
+	if (tbl == NULL) {
+		IP_VS_ERR("ip_vs_dh_init_svc(): no memory\n");
+		return -ENOMEM;
+	}
+	svc->sched_data = tbl;
+	IP_VS_DBG(6, "DH hash table (memory=%dbytes) allocated for "
+		  "current service\n",
+		  sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);
+
+	/* assign the hash buckets with the updated service */
+	ip_vs_dh_assign(tbl, svc);
+
+	return 0;
+}
+
+
+static int ip_vs_dh_done_svc(struct ip_vs_service *svc)
+{
+	struct ip_vs_dh_bucket *tbl = svc->sched_data;
+
+	/* got to clean up hash buckets here */
+	ip_vs_dh_flush(tbl);
+
+	/* release the table itself */
+	kfree(svc->sched_data);
+	IP_VS_DBG(6, "DH hash table (memory=%dbytes) released\n",
+		  sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);
+
+	return 0;
+}
+
+
+static int ip_vs_dh_update_svc(struct ip_vs_service *svc)
+{
+	struct ip_vs_dh_bucket *tbl = svc->sched_data;
+
+	/* got to clean up hash buckets here */
+	ip_vs_dh_flush(tbl);
+
+	/* assign the hash buckets with the updated service */
+	ip_vs_dh_assign(tbl, svc);
+
+	return 0;
+}
+
+
+/*
+ *      If the number of active connections is twice larger than its weight,
+ *      consider that the server is overloaded here.
+ */
+static inline int is_overloaded(struct ip_vs_dest *dest)
+{
+	if (atomic_read(&dest->activeconns) > atomic_read(&dest->weight)*2) {
+		return 1;
+	}
+	return 0;
+}
+
+
+/*
+ *      Destination hashing scheduling
+ */
+static struct ip_vs_dest *
+ip_vs_dh_schedule(struct ip_vs_service *svc, struct iphdr *iph)
+{
+	struct ip_vs_dest *dest;
+	struct ip_vs_dh_bucket *tbl;
+
+	IP_VS_DBG(6, "ip_vs_dh_schedule(): Scheduling...\n");
+
+	tbl = (struct ip_vs_dh_bucket *)svc->sched_data;
+	dest = ip_vs_dh_get(tbl, iph->daddr);
+	if (!dest
+	    || !(dest->flags & IP_VS_DEST_F_AVAILABLE)
+	    || atomic_read(&dest->weight) <= 0
+	    || is_overloaded(dest)) {
+		return NULL;
+	}
+
+	IP_VS_DBG(6, "DH: destination IP address %u.%u.%u.%u "
+		  "--> server %u.%u.%u.%u:%d\n",
+		  NIPQUAD(iph->daddr),
+		  NIPQUAD(dest->addr),
+		  ntohs(dest->port));
+
+	return dest;
+}
+
+
+/*
+ *      IPVS DH Scheduler structure
+ */
+static struct ip_vs_scheduler ip_vs_dh_scheduler =
+{
+	{0},                    /* n_list */
+	"dh",                   /* name */
+	ATOMIC_INIT(0),         /* refcnt */
+	THIS_MODULE,            /* this module */
+	ip_vs_dh_init_svc,      /* service initializer */
+	ip_vs_dh_done_svc,      /* service done */
+	ip_vs_dh_update_svc,    /* service updater */
+	ip_vs_dh_schedule,      /* select a server from the destination list */
+};
+
+
+static int __init ip_vs_dh_init(void)
+{
+	INIT_LIST_HEAD(&ip_vs_dh_scheduler.n_list);
+	return register_ip_vs_scheduler(&ip_vs_dh_scheduler);
+}
+
+
+static void __exit ip_vs_dh_cleanup(void)
+{
+	unregister_ip_vs_scheduler(&ip_vs_dh_scheduler);
+}
+
+
+module_init(ip_vs_dh_init);
+module_exit(ip_vs_dh_cleanup);
+MODULE_LICENSE("GPL");