ia64/linux-2.6.18-xen.hg

annotate usr/initramfs_data.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
rev   line source
ian@0 1 /*
ian@0 2 initramfs_data includes the compressed binary that is the
ian@0 3 filesystem used for early user space.
ian@0 4 Note: Older versions of "as" (prior to binutils 2.11.90.0.23
ian@0 5 released on 2001-07-14) dit not support .incbin.
ian@0 6 If you are forced to use older binutils than that then the
ian@0 7 following trick can be applied to create the resulting binary:
ian@0 8
ian@0 9
ian@0 10 ld -m elf_i386 --format binary --oformat elf32-i386 -r \
ian@0 11 -T initramfs_data.scr initramfs_data.cpio.gz -o initramfs_data.o
ian@0 12 ld -m elf_i386 -r -o built-in.o initramfs_data.o
ian@0 13
ian@0 14 initramfs_data.scr looks like this:
ian@0 15 SECTIONS
ian@0 16 {
ian@0 17 .init.ramfs : { *(.data) }
ian@0 18 }
ian@0 19
ian@0 20 The above example is for i386 - the parameters vary from architectures.
ian@0 21 Eventually look up LDFLAGS_BLOB in an older version of the
ian@0 22 arch/$(ARCH)/Makefile to see the flags used before .incbin was introduced.
ian@0 23
ian@0 24 Using .incbin has the advantage over ld that the correct flags are set
ian@0 25 in the ELF header, as required by certain architectures.
ian@0 26 */
ian@0 27
ian@0 28 .section .init.ramfs,"a"
ian@0 29 .incbin "usr/initramfs_data.cpio.gz"
ian@0 30