view drivers/pci/Kconfig @ 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 c7c92f868aa1
line source
1 #
2 # PCI configuration
3 #
4 config PCI_MSI
5 bool "Message Signaled Interrupts (MSI and MSI-X)"
6 depends on PCI
7 depends on (X86_LOCAL_APIC && X86_IO_APIC) || IA64
8 help
9 This allows device drivers to enable MSI (Message Signaled
10 Interrupts). Message Signaled Interrupts enable a device to
11 generate an interrupt using an inbound Memory Write on its
12 PCI bus instead of asserting a device IRQ pin.
14 Use of PCI MSI interrupts can be disabled at kernel boot time
15 by using the 'pci=nomsi' option. This disables MSI for the
16 entire system.
18 If you don't know what to do here, say N.
20 config PCI_REASSIGN
21 bool
23 config PCI_DEBUG
24 bool "PCI Debugging"
25 depends on PCI && DEBUG_KERNEL
26 help
27 Say Y here if you want the PCI core to produce a bunch of debug
28 messages to the system log. Select this if you are having a
29 problem with PCI support and want to see more of what is going on.
31 When in doubt, say N.
33 config PCI_GUESTDEV
34 bool "PCI Device Reservation for Passthrough"
35 depends on PCI && ACPI
36 default y
37 help
38 Say Y here if you want to reserve PCI device for passthrough.
40 config PCI_IOMULTI
41 bool "PCI Device IO Multiplex for Passthrough"
42 depends on PCI && ACPI
43 default y
44 help
45 Say Y here if you need io multiplexing.
47 config PCI_RESERVE
48 bool "PCI IO/MEMORY space reserve"
49 depends on PCI
50 default y
51 help
52 Say Y here if you need PCI IO/MEMORY space reserve
54 config PCI_IOV
55 bool "PCI IOV support"
56 depends on PCI
57 help
58 I/O Virtualization is a PCI feature supported by some devices
59 which allows them to create virtual devices which share their
60 physical resources.
62 If unsure, say N.