ia64/linux-2.6.18-xen.hg

view arch/sparc64/Kconfig.debug @ 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 menu "Kernel hacking"
3 source "lib/Kconfig.debug"
5 config DEBUG_STACK_USAGE
6 bool "Enable stack utilization instrumentation"
7 depends on DEBUG_KERNEL
8 help
9 Enables the display of the minimum amount of free stack which each
10 task has ever had available in the sysrq-T and sysrq-P debug output.
12 This option will slow down process creation somewhat.
14 config DEBUG_DCFLUSH
15 bool "D-cache flush debugging"
16 depends on DEBUG_KERNEL
18 config STACK_DEBUG
19 depends on DEBUG_KERNEL
20 bool "Stack Overflow Detection Support"
22 config DEBUG_BOOTMEM
23 depends on DEBUG_KERNEL
24 bool "Debug BOOTMEM initialization"
26 config DEBUG_PAGEALLOC
27 bool "Debug page memory allocations"
28 depends on DEBUG_KERNEL && !SOFTWARE_SUSPEND
29 help
30 Unmap pages from the kernel linear mapping after free_pages().
31 This results in a large slowdown, but helps to find certain types
32 of memory corruptions.
34 config MCOUNT
35 bool
36 depends on STACK_DEBUG
37 default y
39 config FRAME_POINTER
40 bool
41 depends on MCOUNT
42 default y
44 endmenu