view Documentation/networking/dgrs.txt @ 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 The Digi International RightSwitch SE-X (dgrs) Device Driver
3 This is a Linux driver for the Digi International RightSwitch SE-X
4 EISA and PCI boards. These are 4 (EISA) or 6 (PCI) port Ethernet
5 switches and a NIC combined into a single board. This driver can
6 be compiled into the kernel statically or as a loadable module.
8 There is also a companion management tool, called "xrightswitch".
9 The management tool lets you watch the performance graphically,
10 as well as set the SNMP agent IP and IPX addresses, IEEE Spanning
11 Tree, and Aging time. These can also be set from the command line
12 when the driver is loaded. The driver command line options are:
14 debug=NNN Debug printing level
15 dma=0/1 Disable/Enable DMA on PCI card
16 spantree=0/1 Disable/Enable IEEE spanning tree
17 hashexpire=NNN Change address aging time (default 300 seconds)
18 ipaddr=A,B,C,D Set SNMP agent IP address i.e. 199,86,8,221
19 iptrap=A,B,C,D Set SNMP agent IP trap address i.e. 199,86,8,221
20 ipxnet=NNN Set SNMP agent IPX network number
21 nicmode=0/1 Disable/Enable multiple NIC mode
23 There is also a tool for setting up input and output packet filters
24 on each port, called "dgrsfilt".
26 Both the management tool and the filtering tool are available
27 separately from the following FTP site:
29 ftp://ftp.dgii.com/drivers/rightswitch/linux/
31 When nicmode=1, the board and driver operate as 4 or 6 individual
32 NIC ports (eth0...eth5) instead of as a switch. All switching
33 functions are disabled. In the future, the board firmware may include
34 a routing cache when in this mode.
36 Copyright 1995-1996 Digi International Inc.
38 This software may be used and distributed according to the terms
39 of the GNU General Public License, incorporated herein by reference.
41 For information on purchasing a RightSwitch SE-4 or SE-6
42 board, please contact Digi's sales department at 1-612-912-3444
43 or 1-800-DIGIBRD. Outside the U.S., please check our Web page at:
45 http://www.dgii.com
47 for sales offices worldwide. Tech support is also available through
48 the channels listed on the Web site, although as long as I am
49 employed on networking products at Digi I will be happy to provide
50 any bug fixes that may be needed.
52 -Rick Richardson, rick@dgii.com