ia64/linux-2.6.18-xen.hg

view drivers/net/dummy.c @ 897:329ea0ccb344

balloon: try harder to balloon up under memory pressure.

Currently if the balloon driver is unable to increase the guest's
reservation it assumes the failure was due to reaching its full
allocation, gives up on the ballooning operation and records the limit
it reached as the "hard limit". The driver will not try again until
the target is set again (even to the same value).

However it is possible that ballooning has in fact failed due to
memory pressure in the host and therefore it is desirable to keep
attempting to reach the target in case memory becomes available. The
most likely scenario is that some guests are ballooning down while
others are ballooning up and therefore there is temporary memory
pressure while things stabilise. You would not expect a well behaved
toolstack to ask a domain to balloon to more than its allocation nor
would you expect it to deliberately over-commit memory by setting
balloon targets which exceed the total host memory.

This patch drops the concept of a hard limit and causes the balloon
driver to retry increasing the reservation on a timer in the same
manner as when decreasing the reservation.

Also if we partially succeed in increasing the reservation
(i.e. receive less pages than we asked for) then we may as well keep
those pages rather than returning them to Xen.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Fri Jun 05 14:01:20 2009 +0100 (2009-06-05)
parents 831230e53067
children
line source
1 /* dummy.c: a dummy net driver
3 The purpose of this driver is to provide a device to point a
4 route through, but not to actually transmit packets.
6 Why? If you have a machine whose only connection is an occasional
7 PPP/SLIP/PLIP link, you can only connect to your own hostname
8 when the link is up. Otherwise you have to use localhost.
9 This isn't very consistent.
11 One solution is to set up a dummy link using PPP/SLIP/PLIP,
12 but this seems (to me) too much overhead for too little gain.
13 This driver provides a small alternative. Thus you can do
15 [when not running slip]
16 ifconfig dummy slip.addr.ess.here up
17 [to go to slip]
18 ifconfig dummy down
19 dip whatever
21 This was written by looking at Donald Becker's skeleton driver
22 and the loopback driver. I then threw away anything that didn't
23 apply! Thanks to Alan Cox for the key clue on what to do with
24 misguided packets.
26 Nick Holloway, 27th May 1994
27 [I tweaked this explanation a little but that's all]
28 Alan Cox, 30th May 1994
29 */
31 #include <linux/module.h>
32 #include <linux/kernel.h>
33 #include <linux/netdevice.h>
34 #include <linux/etherdevice.h>
35 #include <linux/init.h>
36 #include <linux/moduleparam.h>
38 static int numdummies = 1;
40 static int dummy_xmit(struct sk_buff *skb, struct net_device *dev);
41 static struct net_device_stats *dummy_get_stats(struct net_device *dev);
43 static int dummy_set_address(struct net_device *dev, void *p)
44 {
45 struct sockaddr *sa = p;
47 if (!is_valid_ether_addr(sa->sa_data))
48 return -EADDRNOTAVAIL;
50 memcpy(dev->dev_addr, sa->sa_data, ETH_ALEN);
51 return 0;
52 }
54 /* fake multicast ability */
55 static void set_multicast_list(struct net_device *dev)
56 {
57 }
59 static void __init dummy_setup(struct net_device *dev)
60 {
61 /* Initialize the device structure. */
62 dev->get_stats = dummy_get_stats;
63 dev->hard_start_xmit = dummy_xmit;
64 dev->set_multicast_list = set_multicast_list;
65 dev->set_mac_address = dummy_set_address;
67 /* Fill in device structure with ethernet-generic values. */
68 ether_setup(dev);
69 dev->tx_queue_len = 0;
70 dev->change_mtu = NULL;
71 dev->flags |= IFF_NOARP;
72 dev->flags &= ~IFF_MULTICAST;
73 SET_MODULE_OWNER(dev);
74 random_ether_addr(dev->dev_addr);
75 }
77 static int dummy_xmit(struct sk_buff *skb, struct net_device *dev)
78 {
79 struct net_device_stats *stats = netdev_priv(dev);
81 stats->tx_packets++;
82 stats->tx_bytes+=skb->len;
84 dev_kfree_skb(skb);
85 return 0;
86 }
88 static struct net_device_stats *dummy_get_stats(struct net_device *dev)
89 {
90 return netdev_priv(dev);
91 }
93 static struct net_device **dummies;
95 /* Number of dummy devices to be set up by this module. */
96 module_param(numdummies, int, 0);
97 MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
99 static int __init dummy_init_one(int index)
100 {
101 struct net_device *dev_dummy;
102 int err;
104 dev_dummy = alloc_netdev(sizeof(struct net_device_stats),
105 "dummy%d", dummy_setup);
107 if (!dev_dummy)
108 return -ENOMEM;
110 if ((err = register_netdev(dev_dummy))) {
111 free_netdev(dev_dummy);
112 dev_dummy = NULL;
113 } else {
114 dummies[index] = dev_dummy;
115 }
117 return err;
118 }
120 static void dummy_free_one(int index)
121 {
122 unregister_netdev(dummies[index]);
123 free_netdev(dummies[index]);
124 }
126 static int __init dummy_init_module(void)
127 {
128 int i, err = 0;
129 dummies = kmalloc(numdummies * sizeof(void *), GFP_KERNEL);
130 if (!dummies)
131 return -ENOMEM;
132 for (i = 0; i < numdummies && !err; i++)
133 err = dummy_init_one(i);
134 if (err) {
135 i--;
136 while (--i >= 0)
137 dummy_free_one(i);
138 }
139 return err;
140 }
142 static void __exit dummy_cleanup_module(void)
143 {
144 int i;
145 for (i = 0; i < numdummies; i++)
146 dummy_free_one(i);
147 kfree(dummies);
148 }
150 module_init(dummy_init_module);
151 module_exit(dummy_cleanup_module);
152 MODULE_LICENSE("GPL");