ia64/linux-2.6.18-xen.hg

view drivers/mca/mca-bus.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 /* -*- mode: c; c-basic-offset: 8 -*- */
3 /*
4 * MCA bus support functions for sysfs.
5 *
6 * (C) 2002 James Bottomley <James.Bottomley@HansenPartnership.com>
7 *
8 **-----------------------------------------------------------------------------
9 **
10 ** This program is free software; you can redistribute it and/or modify
11 ** it under the terms of the GNU General Public License as published by
12 ** the Free Software Foundation; either version 2 of the License, or
13 ** (at your option) any later version.
14 **
15 ** This program is distributed in the hope that it will be useful,
16 ** but WITHOUT ANY WARRANTY; without even the implied warranty of
17 ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 ** GNU General Public License for more details.
19 **
20 ** You should have received a copy of the GNU General Public License
21 ** along with this program; if not, write to the Free Software
22 ** Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23 **
24 **-----------------------------------------------------------------------------
25 */
27 #include <linux/kernel.h>
28 #include <linux/device.h>
29 #include <linux/mca.h>
30 #include <linux/module.h>
31 #include <linux/init.h>
32 #include <linux/slab.h>
34 /* Very few machines have more than one MCA bus. However, there are
35 * those that do (Voyager 35xx/5xxx), so we do it this way for future
36 * expansion. None that I know have more than 2 */
37 static struct mca_bus *mca_root_busses[MAX_MCA_BUSSES];
39 #define MCA_DEVINFO(i,s) { .pos = i, .name = s }
41 struct mca_device_info {
42 short pos_id; /* the 2 byte pos id for this card */
43 char name[DEVICE_NAME_SIZE];
44 };
46 static int mca_bus_match (struct device *dev, struct device_driver *drv)
47 {
48 struct mca_device *mca_dev = to_mca_device (dev);
49 struct mca_driver *mca_drv = to_mca_driver (drv);
50 const short *mca_ids = mca_drv->id_table;
51 int i;
53 if (!mca_ids)
54 return 0;
56 for(i = 0; mca_ids[i]; i++) {
57 if (mca_ids[i] == mca_dev->pos_id) {
58 mca_dev->index = i;
59 return 1;
60 }
61 }
63 return 0;
64 }
66 struct bus_type mca_bus_type = {
67 .name = "MCA",
68 .match = mca_bus_match,
69 };
70 EXPORT_SYMBOL (mca_bus_type);
72 static ssize_t mca_show_pos_id(struct device *dev, struct device_attribute *attr, char *buf)
73 {
74 /* four digits, \n and trailing \0 */
75 struct mca_device *mca_dev = to_mca_device(dev);
76 int len;
78 if(mca_dev->pos_id < MCA_DUMMY_POS_START)
79 len = sprintf(buf, "%04x\n", mca_dev->pos_id);
80 else
81 len = sprintf(buf, "none\n");
82 return len;
83 }
84 static ssize_t mca_show_pos(struct device *dev, struct device_attribute *attr, char *buf)
85 {
86 /* enough for 8 two byte hex chars plus space and new line */
87 int j, len=0;
88 struct mca_device *mca_dev = to_mca_device(dev);
90 for(j=0; j<8; j++)
91 len += sprintf(buf+len, "%02x ", mca_dev->pos[j]);
92 /* change last trailing space to new line */
93 buf[len-1] = '\n';
94 return len;
95 }
97 static DEVICE_ATTR(id, S_IRUGO, mca_show_pos_id, NULL);
98 static DEVICE_ATTR(pos, S_IRUGO, mca_show_pos, NULL);
100 int __init mca_register_device(int bus, struct mca_device *mca_dev)
101 {
102 struct mca_bus *mca_bus = mca_root_busses[bus];
104 mca_dev->dev.parent = &mca_bus->dev;
105 mca_dev->dev.bus = &mca_bus_type;
106 sprintf (mca_dev->dev.bus_id, "%02d:%02X", bus, mca_dev->slot);
107 mca_dev->dma_mask = mca_bus->default_dma_mask;
108 mca_dev->dev.dma_mask = &mca_dev->dma_mask;
109 mca_dev->dev.coherent_dma_mask = mca_dev->dma_mask;
111 if (device_register(&mca_dev->dev))
112 return 0;
114 device_create_file(&mca_dev->dev, &dev_attr_id);
115 device_create_file(&mca_dev->dev, &dev_attr_pos);
117 return 1;
118 }
120 /* */
121 struct mca_bus * __devinit mca_attach_bus(int bus)
122 {
123 struct mca_bus *mca_bus;
125 if (unlikely(mca_root_busses[bus] != NULL)) {
126 /* This should never happen, but just in case */
127 printk(KERN_EMERG "MCA tried to add already existing bus %d\n",
128 bus);
129 dump_stack();
130 return NULL;
131 }
133 mca_bus = kmalloc(sizeof(struct mca_bus), GFP_KERNEL);
134 if (!mca_bus)
135 return NULL;
136 memset(mca_bus, 0, sizeof(struct mca_bus));
137 sprintf(mca_bus->dev.bus_id,"mca%d",bus);
138 sprintf(mca_bus->name,"Host %s MCA Bridge", bus ? "Secondary" : "Primary");
139 device_register(&mca_bus->dev);
141 mca_root_busses[bus] = mca_bus;
143 return mca_bus;
144 }
146 int __init mca_system_init (void)
147 {
148 return bus_register(&mca_bus_type);
149 }