ia64/linux-2.6.18-xen.hg

view drivers/md/dm-linear.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 /*
2 * Copyright (C) 2001-2003 Sistina Software (UK) Limited.
3 *
4 * This file is released under the GPL.
5 */
7 #include "dm.h"
9 #include <linux/module.h>
10 #include <linux/init.h>
11 #include <linux/blkdev.h>
12 #include <linux/bio.h>
13 #include <linux/slab.h>
15 #define DM_MSG_PREFIX "linear"
17 /*
18 * Linear: maps a linear range of a device.
19 */
20 struct linear_c {
21 struct dm_dev *dev;
22 sector_t start;
23 };
25 /*
26 * Construct a linear mapping: <dev_path> <offset>
27 */
28 static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
29 {
30 struct linear_c *lc;
31 unsigned long long tmp;
33 if (argc != 2) {
34 ti->error = "Invalid argument count";
35 return -EINVAL;
36 }
38 lc = kmalloc(sizeof(*lc), GFP_KERNEL);
39 if (lc == NULL) {
40 ti->error = "dm-linear: Cannot allocate linear context";
41 return -ENOMEM;
42 }
44 if (sscanf(argv[1], "%llu", &tmp) != 1) {
45 ti->error = "dm-linear: Invalid device sector";
46 goto bad;
47 }
48 lc->start = tmp;
50 if (dm_get_device(ti, argv[0], lc->start, ti->len,
51 dm_table_get_mode(ti->table), &lc->dev)) {
52 ti->error = "dm-linear: Device lookup failed";
53 goto bad;
54 }
56 ti->private = lc;
57 return 0;
59 bad:
60 kfree(lc);
61 return -EINVAL;
62 }
64 static void linear_dtr(struct dm_target *ti)
65 {
66 struct linear_c *lc = (struct linear_c *) ti->private;
68 dm_put_device(ti, lc->dev);
69 kfree(lc);
70 }
72 static int linear_map(struct dm_target *ti, struct bio *bio,
73 union map_info *map_context)
74 {
75 struct linear_c *lc = (struct linear_c *) ti->private;
77 bio->bi_bdev = lc->dev->bdev;
78 bio->bi_sector = lc->start + (bio->bi_sector - ti->begin);
80 return 1;
81 }
83 static int linear_status(struct dm_target *ti, status_type_t type,
84 char *result, unsigned int maxlen)
85 {
86 struct linear_c *lc = (struct linear_c *) ti->private;
88 switch (type) {
89 case STATUSTYPE_INFO:
90 result[0] = '\0';
91 break;
93 case STATUSTYPE_TABLE:
94 snprintf(result, maxlen, "%s %llu", lc->dev->name,
95 (unsigned long long)lc->start);
96 break;
97 }
98 return 0;
99 }
101 static struct target_type linear_target = {
102 .name = "linear",
103 .version= {1, 0, 1},
104 .module = THIS_MODULE,
105 .ctr = linear_ctr,
106 .dtr = linear_dtr,
107 .map = linear_map,
108 .status = linear_status,
109 };
111 int __init dm_linear_init(void)
112 {
113 int r = dm_register_target(&linear_target);
115 if (r < 0)
116 DMERR("register failed %d", r);
118 return r;
119 }
121 void dm_linear_exit(void)
122 {
123 int r = dm_unregister_target(&linear_target);
125 if (r < 0)
126 DMERR("unregister failed %d", r);
127 }