view Documentation/networking/alias.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
2 IP-Aliasing:
3 ============
5 IP-aliases are additional IP-addresses/masks hooked up to a base
6 interface by adding a colon and a string when running ifconfig.
7 This string is usually numeric, but this is not a must.
9 IP-Aliases are avail if CONFIG_INET (`standard' IPv4 networking)
10 is configured in the kernel.
13 o Alias creation.
14 Alias creation is done by 'magic' interface naming: eg. to create a
15 alias for eth0 ...
17 # ifconfig eth0:0 etc,etc....
18 ~~ -> request alias #0 creation (if not yet exists) for eth0
20 The corresponding route is also set up by this command.
21 Please note: The route always points to the base interface.
24 o Alias deletion.
25 The alias is removed by shutting the alias down:
27 # ifconfig eth0:0 down
28 ~~~~~~~~~~ -> will delete alias
31 o Alias (re-)configuring
33 Aliases are not real devices, but programs should be able to configure and
34 refer to them as usual (ifconfig, route, etc).
37 o Relationship with main device
39 If the base device is shut down the added aliases will be deleted
40 too.
43 Contact
44 -------
45 Please finger or e-mail me:
46 Juan Jose Ciarlante <jjciarla@raiz.uncu.edu.ar>
48 Updated by Erik Schoenfelder <schoenfr@gaertner.DE>
50 ; local variables:
51 ; mode: indented-text
52 ; mode: auto-fill
53 ; end: