view Documentation/networking/wavelan.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 Wavelan drivers saga
2 ------------------------
4 By Jean Tourrilhes <jt@hpl.hp.com>
6 The Wavelan is a Radio network adapter designed by
7 Lucent. Under this generic name is hidden quite a variety of hardware,
8 and many Linux driver to support it.
9 The get the full story on Wireless LANs, please consult :
10 http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/
12 "wavelan" driver (old ISA Wavelan)
13 ----------------
14 o Config : Network device -> Wireless LAN -> AT&T WaveLAN
15 o Location : .../drivers/net/wavelan*
16 o in-line doc : .../drivers/net/wavelan.p.h
17 o on-line doc :
18 http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Wavelan.html
20 This is the driver for the ISA version of the first generation
21 of the Wavelan, now discontinued. The device is 2 Mb/s, composed of a
22 Intel 82586 controller and a Lucent Modem, and is NOT 802.11 compliant.
23 The driver has been tested with the following hardware :
24 o Wavelan ISA 915 MHz (full length ISA card)
25 o Wavelan ISA 915 MHz 2.0 (half length ISA card)
26 o Wavelan ISA 2.4 GHz (full length ISA card, fixed frequency)
27 o Wavelan ISA 2.4 GHz 2.0 (half length ISA card, frequency selectable)
28 o Above cards with the optional DES encryption feature
30 "wavelan_cs" driver (old Pcmcia Wavelan)
31 -------------------
32 o Config : Network device -> PCMCIA network ->
33 Pcmcia Wireless LAN -> AT&T/Lucent WaveLAN
34 o Location : .../drivers/net/pcmcia/wavelan*
35 o in-line doc : .../drivers/net/pcmcia/wavelan_cs.h
36 o on-line doc :
37 http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Wavelan.html
39 This is the driver for the PCMCIA version of the first
40 generation of the Wavelan, now discontinued. The device is 2 Mb/s,
41 composed of a Intel 82593 controller (totally different from the 82586)
42 and a Lucent Modem, and NOT 802.11 compatible.
43 The driver has been tested with the following hardware :
44 o Wavelan Pcmcia 915 MHz 2.0 (Pcmcia card + separate
45 modem/antenna block)
46 o Wavelan Pcmcia 2.4 GHz 2.0 (Pcmcia card + separate
47 modem/antenna block)
49 "wvlan_cs" driver (Wavelan IEEE, GPL)
50 -----------------
51 o Config : Not yet in kernel
52 o Location : Pcmcia package 3.1.10+
53 o on-line doc : http://www.fasta.fh-dortmund.de/users/andy/wvlan/
55 This is the driver for the current generation of Wavelan IEEE,
56 which is 802.11 compatible. Depending on version, it is 2 Mb/s or 11
57 Mb/s, with or without encryption, all implemented in Lucent specific
58 DSP (the Hermes).
59 This is a GPL full source PCMCIA driver (ISA is just a Pcmcia
60 card with ISA-Pcmcia bridge).
62 "wavelan2_cs" driver (Wavelan IEEE, binary)
63 --------------------
64 o Config : Not yet in kernel
65 o Location : ftp://sourceforge.org/pcmcia/contrib/
67 This driver support exactly the same hardware as the previous
68 driver, the main difference is that it is based on a binary library
69 and supported by Lucent.
71 I hope it clears the confusion ;-)
73 Jean