view Documentation/networking/framerelay.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 Frame Relay (FR) support for linux is built into a two tiered system of device
2 drivers. The upper layer implements RFC1490 FR specification, and uses the
3 Data Link Connection Identifier (DLCI) as its hardware address. Usually these
4 are assigned by your network supplier, they give you the number/numbers of
5 the Virtual Connections (VC) assigned to you.
7 Each DLCI is a point-to-point link between your machine and a remote one.
8 As such, a separate device is needed to accommodate the routing. Within the
9 net-tools archives is 'dlcicfg'. This program will communicate with the
10 base "DLCI" device, and create new net devices named 'dlci00', 'dlci01'...
11 The configuration script will ask you how many DLCIs you need, as well as
12 how many DLCIs you want to assign to each Frame Relay Access Device (FRAD).
14 The DLCI uses a number of function calls to communicate with the FRAD, all
15 of which are stored in the FRAD's private data area. assoc/deassoc,
16 activate/deactivate and dlci_config. The DLCI supplies a receive function
17 to the FRAD to accept incoming packets.
19 With this initial offering, only 1 FRAD driver is available. With many thanks
20 to Sangoma Technologies, David Mandelstam & Gene Kozin, the S502A, S502E &
21 S508 are supported. This driver is currently set up for only FR, but as
22 Sangoma makes more firmware modules available, it can be updated to provide
23 them as well.
25 Configuration of the FRAD makes use of another net-tools program, 'fradcfg'.
26 This program makes use of a configuration file (which dlcicfg can also read)
27 to specify the types of boards to be configured as FRADs, as well as perform
28 any board specific configuration. The Sangoma module of fradcfg loads the
29 FR firmware into the card, sets the irq/port/memory information, and provides
30 an initial configuration.
32 Additional FRAD device drivers can be added as hardware is available.
34 At this time, the dlcicfg and fradcfg programs have not been incorporated into
35 the net-tools distribution. They can be found at ftp.invlogic.com, in
36 /pub/linux. Note that with OS/2 FTPD, you end up in /pub by default, so just
37 use 'cd linux'. v0.10 is for use on pre-2.0.3 and earlier, v0.15 is for
38 pre-2.0.4 and later.