ia64/linux-2.6.18-xen.hg

view Documentation/arm/Netwinder @ 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 NetWinder specific documentation
2 ================================
4 The NetWinder is a small low-power computer, primarily designed
5 to run Linux. It is based around the StrongARM RISC processor,
6 DC21285 PCI bridge, with PC-type hardware glued around it.
8 Port usage
9 ==========
11 Min - Max Description
12 ---------------------------
13 0x0000 - 0x000f DMA1
14 0x0020 - 0x0021 PIC1
15 0x0060 - 0x006f Keyboard
16 0x0070 - 0x007f RTC
17 0x0080 - 0x0087 DMA1
18 0x0088 - 0x008f DMA2
19 0x00a0 - 0x00a3 PIC2
20 0x00c0 - 0x00df DMA2
21 0x0180 - 0x0187 IRDA
22 0x01f0 - 0x01f6 ide0
23 0x0201 Game port
24 0x0203 RWA010 configuration read
25 0x0220 - ? SoundBlaster
26 0x0250 - ? WaveArtist
27 0x0279 RWA010 configuration index
28 0x02f8 - 0x02ff Serial ttyS1
29 0x0300 - 0x031f Ether10
30 0x0338 GPIO1
31 0x033a GPIO2
32 0x0370 - 0x0371 W83977F configuration registers
33 0x0388 - ? AdLib
34 0x03c0 - 0x03df VGA
35 0x03f6 ide0
36 0x03f8 - 0x03ff Serial ttyS0
37 0x0400 - 0x0408 DC21143
38 0x0480 - 0x0487 DMA1
39 0x0488 - 0x048f DMA2
40 0x0a79 RWA010 configuration write
41 0xe800 - 0xe80f ide0/ide1 BM DMA
44 Interrupt usage
45 ===============
47 IRQ type Description
48 ---------------------------
49 0 ISA 100Hz timer
50 1 ISA Keyboard
51 2 ISA cascade
52 3 ISA Serial ttyS1
53 4 ISA Serial ttyS0
54 5 ISA PS/2 mouse
55 6 ISA IRDA
56 7 ISA Printer
57 8 ISA RTC alarm
58 9 ISA
59 10 ISA GP10 (Orange reset button)
60 11 ISA
61 12 ISA WaveArtist
62 13 ISA
63 14 ISA hda1
64 15 ISA
66 DMA usage
67 =========
69 DMA type Description
70 ---------------------------
71 0 ISA IRDA
72 1 ISA
73 2 ISA cascade
74 3 ISA WaveArtist
75 4 ISA
76 5 ISA
77 6 ISA
78 7 ISA WaveArtist