view Documentation/networking/routing.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 directory ftp.inr.ac.ru:/ip-routing contains:
3 - iproute.c - "professional" routing table maintenance utility.
5 - rdisc.tar.gz - rdisc daemon, ported from Sun.
8 - routing.tgz - original Mike McLagan's route by source patch.
9 Currently it is obsolete.
11 - gated.dif-ss<NEWEST>.gz - gated-R3_6Alpha_2 fixes.
12 Look at README.gated
14 - mrouted-3.8.dif.gz - mrouted-3.8 fixes.
16 - rtmon.c - trivial debugging utility: reads and stores netlink.
19 NEWS for user.
21 - Policy based routing. Routing decisions are made on the basis
22 not only of destination address, but also source address,
23 TOS and incoming interface.
24 - Complete set of IP level control messages.
25 Now Linux is the only OS in the world complying to RFC requirements.
26 Great win 8)
27 - New interface addressing paradigm.
28 Assignment of address ranges to interface,
29 multiple prefixes etc. etc.
30 Do not bother, it is compatible with the old one. Moreover:
31 - You don't need to do "route add aaa.bbb.ccc... eth0" anymore,
32 it is done automatically.
33 - "Abstract" UNIX sockets and security enhancements.
34 This is necessary to use TIRPC and TLI emulation library.
36 NEWS for hacker.
38 - New destination cache. Flexible, robust and just beautiful.
39 - Network stack is reordered, simplified, optimized, a lot of bugs fixed.
40 (well, and new bugs were introduced, but I haven't seen them yet 8))
41 It is difficult to describe all the changes, look into source.
43 If you see this file, then this patch works 8)
45 Alexey Kuznetsov.
46 kuznet@ms2.inr.ac.ru