ia64/linux-2.6.18-xen.hg

view drivers/mtd/maps/uclinux.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 /****************************************************************************/
3 /*
4 * uclinux.c -- generic memory mapped MTD driver for uclinux
5 *
6 * (C) Copyright 2002, Greg Ungerer (gerg@snapgear.com)
7 *
8 * $Id: uclinux.c,v 1.12 2005/11/07 11:14:29 gleixner Exp $
9 */
11 /****************************************************************************/
13 #include <linux/module.h>
14 #include <linux/types.h>
15 #include <linux/init.h>
16 #include <linux/kernel.h>
17 #include <linux/fs.h>
18 #include <linux/major.h>
19 #include <linux/root_dev.h>
20 #include <linux/mtd/mtd.h>
21 #include <linux/mtd/map.h>
22 #include <linux/mtd/partitions.h>
23 #include <asm/io.h>
25 /****************************************************************************/
27 struct map_info uclinux_ram_map = {
28 .name = "RAM",
29 };
31 struct mtd_info *uclinux_ram_mtdinfo;
33 /****************************************************************************/
35 struct mtd_partition uclinux_romfs[] = {
36 { .name = "ROMfs" }
37 };
39 #define NUM_PARTITIONS ARRAY_SIZE(uclinux_romfs)
41 /****************************************************************************/
43 int uclinux_point(struct mtd_info *mtd, loff_t from, size_t len,
44 size_t *retlen, u_char **mtdbuf)
45 {
46 struct map_info *map = mtd->priv;
47 *mtdbuf = (u_char *) (map->virt + ((int) from));
48 *retlen = len;
49 return(0);
50 }
52 /****************************************************************************/
54 int __init uclinux_mtd_init(void)
55 {
56 struct mtd_info *mtd;
57 struct map_info *mapp;
58 extern char _ebss;
59 unsigned long addr = (unsigned long) &_ebss;
61 mapp = &uclinux_ram_map;
62 mapp->phys = addr;
63 mapp->size = PAGE_ALIGN(ntohl(*((unsigned long *)(addr + 8))));
64 mapp->bankwidth = 4;
66 printk("uclinux[mtd]: RAM probe address=0x%x size=0x%x\n",
67 (int) mapp->phys, (int) mapp->size);
69 mapp->virt = ioremap_nocache(mapp->phys, mapp->size);
71 if (mapp->virt == 0) {
72 printk("uclinux[mtd]: ioremap_nocache() failed\n");
73 return(-EIO);
74 }
76 simple_map_init(mapp);
78 mtd = do_map_probe("map_ram", mapp);
79 if (!mtd) {
80 printk("uclinux[mtd]: failed to find a mapping?\n");
81 iounmap(mapp->virt);
82 return(-ENXIO);
83 }
85 mtd->owner = THIS_MODULE;
86 mtd->point = uclinux_point;
87 mtd->priv = mapp;
89 uclinux_ram_mtdinfo = mtd;
90 add_mtd_partitions(mtd, uclinux_romfs, NUM_PARTITIONS);
92 printk("uclinux[mtd]: set %s to be root filesystem\n",
93 uclinux_romfs[0].name);
94 ROOT_DEV = MKDEV(MTD_BLOCK_MAJOR, 0);
96 return(0);
97 }
99 /****************************************************************************/
101 void __exit uclinux_mtd_cleanup(void)
102 {
103 if (uclinux_ram_mtdinfo) {
104 del_mtd_partitions(uclinux_ram_mtdinfo);
105 map_destroy(uclinux_ram_mtdinfo);
106 uclinux_ram_mtdinfo = NULL;
107 }
108 if (uclinux_ram_map.virt) {
109 iounmap((void *) uclinux_ram_map.virt);
110 uclinux_ram_map.virt = 0;
111 }
112 }
114 /****************************************************************************/
116 module_init(uclinux_mtd_init);
117 module_exit(uclinux_mtd_cleanup);
119 MODULE_LICENSE("GPL");
120 MODULE_AUTHOR("Greg Ungerer <gerg@snapgear.com>");
121 MODULE_DESCRIPTION("Generic RAM based MTD for uClinux");
123 /****************************************************************************/