ia64/linux-2.6.18-xen.hg

view init/do_mounts.h @ 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 #include <linux/config.h>
2 #include <linux/kernel.h>
3 #include <linux/init.h>
4 #include <linux/syscalls.h>
5 #include <linux/unistd.h>
6 #include <linux/slab.h>
7 #include <linux/mount.h>
8 #include <linux/major.h>
9 #include <linux/root_dev.h>
11 void change_floppy(char *fmt, ...);
12 void mount_block_root(char *name, int flags);
13 void mount_root(void);
14 extern int root_mountflags;
15 extern char *root_device_name;
17 static inline int create_dev(char *name, dev_t dev)
18 {
19 sys_unlink(name);
20 return sys_mknod(name, S_IFBLK|0600, new_encode_dev(dev));
21 }
23 #if BITS_PER_LONG == 32
24 static inline u32 bstat(char *name)
25 {
26 struct stat64 stat;
27 if (sys_stat64(name, &stat) != 0)
28 return 0;
29 if (!S_ISBLK(stat.st_mode))
30 return 0;
31 if (stat.st_rdev != (u32)stat.st_rdev)
32 return 0;
33 return stat.st_rdev;
34 }
35 #else
36 static inline u32 bstat(char *name)
37 {
38 struct stat stat;
39 if (sys_newstat(name, &stat) != 0)
40 return 0;
41 if (!S_ISBLK(stat.st_mode))
42 return 0;
43 return stat.st_rdev;
44 }
45 #endif
47 #ifdef CONFIG_BLK_DEV_RAM
49 int __init rd_load_disk(int n);
50 int __init rd_load_image(char *from);
52 #else
54 static inline int rd_load_disk(int n) { return 0; }
55 static inline int rd_load_image(char *from) { return 0; }
57 #endif
59 #ifdef CONFIG_BLK_DEV_INITRD
61 int __init initrd_load(void);
63 #else
65 static inline int initrd_load(void) { return 0; }
67 #endif
69 #ifdef CONFIG_BLK_DEV_MD
71 void md_run_setup(void);
73 #else
75 static inline void md_run_setup(void) {}
77 #endif