ia64/linux-2.6.18-xen.hg

view arch/mips/sgi-ip27/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 831230e53067
children
line source
1 #config SGI_SN0_XXL
2 # bool "IP27 XXL"
3 # depends on SGI_IP27
4 # This options adds support for userspace processes upto 16TB size.
5 # Normally the limit is just .5TB.
7 choice
8 prompt "Node addressing mode"
9 depends on SGI_IP27
10 default SGI_SN_M_MODE
12 config SGI_SN_M_MODE
13 bool "IP27 M-Mode"
14 help
15 The nodes of Origin, Onyx, Fuel and Tezro systems can be configured
16 in either N-Modes which allows for more nodes or M-Mode which allows
17 for more memory. Your hardware is almost certainly running in
18 M-Mode, so choose M-mode here.
20 config SGI_SN_N_MODE
21 bool "IP27 N-Mode"
22 depends on EXPERIMENTAL
23 help
24 The nodes of Origin, Onyx, Fuel and Tezro systems can be configured
25 in either N-Modes which allows for more nodes or M-Mode which allows
26 for more memory. Your hardware is almost certainly running in
27 M-Mode, so choose M-mode here.
29 endchoice
31 config MAPPED_KERNEL
32 bool "Mapped kernel support"
33 depends on SGI_IP27
34 help
35 Change the way a Linux kernel is loaded into memory on a MIPS64
36 machine. This is required in order to support text replication on
37 NUMA. If you need to understand it, read the source code.
39 config REPLICATE_KTEXT
40 bool "Kernel text replication support"
41 depends on SGI_IP27
42 select MAPPED_KERNEL
43 help
44 Say Y here to enable replicating the kernel text across multiple
45 nodes in a NUMA cluster. This trades memory for speed.
47 config REPLICATE_EXHANDLERS
48 bool "Exception handler replication support"
49 depends on SGI_IP27
50 help
51 Say Y here to enable replicating the kernel exception handlers
52 across multiple nodes in a NUMA cluster. This trades memory for
53 speed.