view drivers/atm/fore200e_firmware_copyright @ 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
2 These microcode data are placed under the terms of the GNU General Public License.
4 We would prefer you not to distribute modified versions of it and not to ask
5 for assembly or other microcode source.
7 Copyright (c) 1995-2000 FORE Systems, Inc., as an unpublished work. This
8 notice does not imply unrestricted or public access to these materials which
9 are a trade secret of FORE Systems, Inc. or its subsidiaries or affiliates
10 (together referred to as "FORE"), and which may not be reproduced, used, sold
11 or transferred to any third party without FORE's prior written consent. All
12 rights reserved.
14 U.S. Government Restricted Rights. If you are licensing the Software on
15 behalf of the U.S. Government ("Government"), the following provisions apply
16 to you. If the software is supplied to the Department of Defense ("DoD"), it
17 is classified as "Commercial Computer Software" under paragraph 252.227-7014
18 of the DoD Supplement to the Federal Acquisition Regulations ("DFARS") (or any
19 successor regulations) and the Government is acquiring only the license
20 rights granted herein (the license rights customarily provided to non-Government
21 users). If the Software is supplied to any unit or agency of the Government
22 other than the DoD, it is classified as "Restricted Computer Software" and
23 the Government's rights in the Software are defined in paragraph 52.227-19 of
24 the Federal Acquisition Regulations ("FAR") (or any successor regulations) or,
25 in the cases of NASA, in paragraph 18.52.227-86 of the NASA Supplement to the FAR
26 (or any successor regulations).
28 FORE Systems is a registered trademark, and ForeRunner, ForeRunnerLE, and
29 ForeThought are trademarks of FORE Systems, Inc. All other brands or product
30 names are trademarks or registered trademarks of their respective holders.