ia64/linux-2.6.18-xen.hg

view REPORTING-BUGS @ 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 [Some of this is taken from Frohwalt Egerer's original linux-kernel FAQ]
3 What follows is a suggested procedure for reporting Linux bugs. You
4 aren't obliged to use the bug reporting format, it is provided as a guide
5 to the kind of information that can be useful to developers - no more.
7 If the failure includes an "OOPS:" type message in your log or on
8 screen please read "Documentation/oops-tracing.txt" before posting your
9 bug report. This explains what you should do with the "Oops" information
10 to make it useful to the recipient.
12 Send the output to the maintainer of the kernel area that seems to
13 be involved with the problem. Don't worry too much about getting the
14 wrong person. If you are unsure send it to the person responsible for the
15 code relevant to what you were doing. If it occurs repeatably try and
16 describe how to recreate it. That is worth even more than the oops itself.
17 The list of maintainers is in the MAINTAINERS file in this directory.
19 If it is a security bug, please copy the Security Contact listed
20 in the MAINTAINERS file. They can help coordinate bugfix and disclosure.
21 See Documentation/SecurityBugs for more information.
23 If you are totally stumped as to whom to send the report, send it to
24 linux-kernel@vger.kernel.org. (For more information on the linux-kernel
25 mailing list see http://www.tux.org/lkml/).
27 This is a suggested format for a bug report sent to the Linux kernel mailing
28 list. Having a standardized bug report form makes it easier for you not to
29 overlook things, and easier for the developers to find the pieces of
30 information they're really interested in. Don't feel you have to follow it.
32 First run the ver_linux script included as scripts/ver_linux, which
33 reports the version of some important subsystems. Run this script with
34 the command "sh scripts/ver_linux".
36 Use that information to fill in all fields of the bug report form, and
37 post it to the mailing list with a subject of "PROBLEM: <one line
38 summary from [1.]>" for easy identification by the developers.
40 [1.] One line summary of the problem:
41 [2.] Full description of the problem/report:
42 [3.] Keywords (i.e., modules, networking, kernel):
43 [4.] Kernel version (from /proc/version):
44 [5.] Most recent kernel version which did not have the bug:
45 [6.] Output of Oops.. message (if applicable) with symbolic information
46 resolved (see Documentation/oops-tracing.txt)
47 [7.] A small shell script or example program which triggers the
48 problem (if possible)
49 [8.] Environment
50 [8.1.] Software (add the output of the ver_linux script here)
51 [8.2.] Processor information (from /proc/cpuinfo):
52 [8.3.] Module information (from /proc/modules):
53 [8.4.] Loaded driver and hardware information (/proc/ioports, /proc/iomem)
54 [8.5.] PCI information ('lspci -vvv' as root)
55 [8.6.] SCSI information (from /proc/scsi/scsi)
56 [8.7.] Other information that might be relevant to the problem
57 (please look in /proc and include all information that you
58 think to be relevant):
59 [X.] Other notes, patches, fixes, workarounds:
62 Thank you