ia64/linux-2.6.18-xen.hg

view arch/sparc64/kernel/pci_sun4v_asm.S @ 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 /* pci_sun4v_asm: Hypervisor calls for PCI support.
2 *
3 * Copyright (C) 2006 David S. Miller <davem@davemloft.net>
4 */
6 #include <asm/hypervisor.h>
8 /* %o0: devhandle
9 * %o1: tsbid
10 * %o2: num ttes
11 * %o3: io_attributes
12 * %o4: io_page_list phys address
13 *
14 * returns %o0: -status if status was non-zero, else
15 * %o0: num pages mapped
16 */
17 .globl pci_sun4v_iommu_map
18 pci_sun4v_iommu_map:
19 mov %o5, %g1
20 mov HV_FAST_PCI_IOMMU_MAP, %o5
21 ta HV_FAST_TRAP
22 brnz,pn %o0, 1f
23 sub %g0, %o0, %o0
24 mov %o1, %o0
25 1: retl
26 nop
28 /* %o0: devhandle
29 * %o1: tsbid
30 * %o2: num ttes
31 *
32 * returns %o0: num ttes demapped
33 */
34 .globl pci_sun4v_iommu_demap
35 pci_sun4v_iommu_demap:
36 mov HV_FAST_PCI_IOMMU_DEMAP, %o5
37 ta HV_FAST_TRAP
38 retl
39 mov %o1, %o0
41 /* %o0: devhandle
42 * %o1: tsbid
43 * %o2: &io_attributes
44 * %o3: &real_address
45 *
46 * returns %o0: status
47 */
48 .globl pci_sun4v_iommu_getmap
49 pci_sun4v_iommu_getmap:
50 mov %o2, %o4
51 mov HV_FAST_PCI_IOMMU_GETMAP, %o5
52 ta HV_FAST_TRAP
53 stx %o1, [%o4]
54 stx %o2, [%o3]
55 retl
56 mov %o0, %o0
58 /* %o0: devhandle
59 * %o1: pci_device
60 * %o2: pci_config_offset
61 * %o3: size
62 *
63 * returns %o0: data
64 *
65 * If there is an error, the data will be returned
66 * as all 1's.
67 */
68 .globl pci_sun4v_config_get
69 pci_sun4v_config_get:
70 mov HV_FAST_PCI_CONFIG_GET, %o5
71 ta HV_FAST_TRAP
72 brnz,a,pn %o1, 1f
73 mov -1, %o2
74 1: retl
75 mov %o2, %o0
77 /* %o0: devhandle
78 * %o1: pci_device
79 * %o2: pci_config_offset
80 * %o3: size
81 * %o4: data
82 *
83 * returns %o0: status
84 *
85 * status will be zero if the operation completed
86 * successfully, else -1 if not
87 */
88 .globl pci_sun4v_config_put
89 pci_sun4v_config_put:
90 mov HV_FAST_PCI_CONFIG_PUT, %o5
91 ta HV_FAST_TRAP
92 brnz,a,pn %o1, 1f
93 mov -1, %o1
94 1: retl
95 mov %o1, %o0