view Documentation/SubmitChecklist @ 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
line source
1 Linux Kernel patch sumbittal checklist
2 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4 Here are some basic things that developers should do if they want to see their
5 kernel patch submissions accepted more quickly.
7 These are all above and beyond the documentation that is provided in
8 Documentation/SubmittingPatches and elsewhere regarding submitting Linux
9 kernel patches.
13 1: Builds cleanly with applicable or modified CONFIG options =y, =m, and
14 =n. No gcc warnings/errors, no linker warnings/errors.
16 2: Passes allnoconfig, allmodconfig
18 3: Builds on multiple CPU architectures by using local cross-compile tools
19 or something like PLM at OSDL.
21 4: ppc64 is a good architecture for cross-compilation checking because it
22 tends to use `unsigned long' for 64-bit quantities.
24 5: Matches kernel coding style(!)
26 6: Any new or modified CONFIG options don't muck up the config menu.
28 7: All new Kconfig options have help text.
30 8: Has been carefully reviewed with respect to relevant Kconfig
31 combinations. This is very hard to get right with testing -- brainpower
32 pays off here.
34 9: Check cleanly with sparse.
36 10: Use 'make checkstack' and 'make namespacecheck' and fix any problems
37 that they find. Note: checkstack does not point out problems explicitly,
38 but any one function that uses more than 512 bytes on the stack is a
39 candidate for change.
41 11: Include kernel-doc to document global kernel APIs. (Not required for
42 static functions, but OK there also.) Use 'make htmldocs' or 'make
43 mandocs' to check the kernel-doc and fix any issues.
45 12: Has been tested with CONFIG_PREEMPT, CONFIG_DEBUG_PREEMPT,
48 enabled.
50 13: Has been build- and runtime tested with and without CONFIG_SMP and
53 14: If the patch affects IO/Disk, etc: has been tested with and without
56 15: All codepaths have been exercised with all lockdep features enabled.
58 16: All new /proc entries are documented under Documentation/
60 17: All new kernel boot parameters are documented in
61 Documentation/kernel-parameters.txt.
63 18: All new module parameters are documented with MODULE_PARM_DESC()