ia64/linux-2.6.18-xen.hg

view init/do_mounts_initrd.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 #define __KERNEL_SYSCALLS__
2 #include <linux/unistd.h>
3 #include <linux/kernel.h>
4 #include <linux/fs.h>
5 #include <linux/minix_fs.h>
6 #include <linux/ext2_fs.h>
7 #include <linux/romfs_fs.h>
8 #include <linux/initrd.h>
9 #include <linux/sched.h>
11 #include "do_mounts.h"
13 unsigned long initrd_start, initrd_end;
14 int initrd_below_start_ok;
15 unsigned int real_root_dev; /* do_proc_dointvec cannot handle kdev_t */
16 static int __initdata old_fd, root_fd;
17 static int __initdata mount_initrd = 1;
19 static int __init no_initrd(char *str)
20 {
21 mount_initrd = 0;
22 return 1;
23 }
25 __setup("noinitrd", no_initrd);
27 static int __init do_linuxrc(void * shell)
28 {
29 static char *argv[] = { "linuxrc", NULL, };
30 extern char * envp_init[];
32 sys_close(old_fd);sys_close(root_fd);
33 sys_close(0);sys_close(1);sys_close(2);
34 sys_setsid();
35 (void) sys_open("/dev/console",O_RDWR,0);
36 (void) sys_dup(0);
37 (void) sys_dup(0);
38 return execve(shell, argv, envp_init);
39 }
41 static void __init handle_initrd(void)
42 {
43 int error;
44 int pid;
46 real_root_dev = new_encode_dev(ROOT_DEV);
47 create_dev("/dev/root.old", Root_RAM0);
48 /* mount initrd on rootfs' /root */
49 mount_block_root("/dev/root.old", root_mountflags & ~MS_RDONLY);
50 sys_mkdir("/old", 0700);
51 root_fd = sys_open("/", 0, 0);
52 old_fd = sys_open("/old", 0, 0);
53 /* move initrd over / and chdir/chroot in initrd root */
54 sys_chdir("/root");
55 sys_mount(".", "/", NULL, MS_MOVE, NULL);
56 sys_chroot(".");
58 current->flags |= PF_NOFREEZE;
59 pid = kernel_thread(do_linuxrc, "/linuxrc", SIGCHLD);
60 if (pid > 0) {
61 while (pid != sys_wait4(-1, NULL, 0, NULL))
62 yield();
63 }
65 /* move initrd to rootfs' /old */
66 sys_fchdir(old_fd);
67 sys_mount("/", ".", NULL, MS_MOVE, NULL);
68 /* switch root and cwd back to / of rootfs */
69 sys_fchdir(root_fd);
70 sys_chroot(".");
71 sys_close(old_fd);
72 sys_close(root_fd);
74 if (new_decode_dev(real_root_dev) == Root_RAM0) {
75 sys_chdir("/old");
76 return;
77 }
79 ROOT_DEV = new_decode_dev(real_root_dev);
80 mount_root();
82 printk(KERN_NOTICE "Trying to move old root to /initrd ... ");
83 error = sys_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL);
84 if (!error)
85 printk("okay\n");
86 else {
87 int fd = sys_open("/dev/root.old", O_RDWR, 0);
88 if (error == -ENOENT)
89 printk("/initrd does not exist. Ignored.\n");
90 else
91 printk("failed\n");
92 printk(KERN_NOTICE "Unmounting old root\n");
93 sys_umount("/old", MNT_DETACH);
94 printk(KERN_NOTICE "Trying to free ramdisk memory ... ");
95 if (fd < 0) {
96 error = fd;
97 } else {
98 error = sys_ioctl(fd, BLKFLSBUF, 0);
99 sys_close(fd);
100 }
101 printk(!error ? "okay\n" : "failed\n");
102 }
103 }
105 int __init initrd_load(void)
106 {
107 if (mount_initrd) {
108 create_dev("/dev/ram", Root_RAM0);
109 /*
110 * Load the initrd data into /dev/ram0. Execute it as initrd
111 * unless /dev/ram0 is supposed to be our actual root device,
112 * in that case the ram disk is just set up here, and gets
113 * mounted in the normal path.
114 */
115 if (rd_load_image("/initrd.image") && ROOT_DEV != Root_RAM0) {
116 sys_unlink("/initrd.image");
117 handle_initrd();
118 return 1;
119 }
120 }
121 sys_unlink("/initrd.image");
122 return 0;
123 }