Bug 507847

Created attachment 349245 [details]
 linux-2.6.18-xen.hg 897:329ea0ccb344 ported to 2.6.9-89.EL

The issue described in the parent bug also effects the RHEL 4x kernel, I tried 2.6.9-89.EL. I have attached a version of the upstream patch appropriate for that kernel.

+++ This bug was initially created as a clone of Bug #507846 +++

Created an attachment (id=349241)
linux-2.6.18-xen.hg 897:329ea0ccb344 ported to  2.6.18-128.1.10.el5

Description of problem:

We recently noticed that the standard Xen balloon driver for Linux will give up on ballooning if it encounters memory pressure. When this occurs ballooning will stop until the target is reset, regardless of how much memory subsequently becomes available

Version-Release number of selected component (if applicable):

2.6.18-128.1.10.el5 and all previous kernel releases.

How reproducible:

Easily

Steps to Reproduce:

Depend somewhat on the amount of the host RAM available. The trick is to balloon a domain down and then create a guest which uses enough memory to cause the original to exhaust memory as it balloons back up.

1. Create a new domain with e.g. 2G RAM
2. Instruct domain to balloon to 1G RAM: xenstore-write /local/domain/<domid>/memory/target 1048576  
3. Create a second domain which uses up enough RAM to leave <1G free.
4. Instruct the original domain to balloon back up to 2G: xenstore-write /local/domain/<domid>/memory/target 2097152  
5. Shutdown domain 2
  
Actual results:

In step 4 the first domain will stop ballooning up somewhere between 1 and 2G, in step 5 it will remain at that same value.

Expected results:

In step 5 the original domain will balloon up to the full 2G.

Additional info:

This was fixed by the upstream changeset
http://xenbits.xensource.com/linux-2.6.18-xen.hg?cs=329ea0ccb344 I have attached a version ported to the 2.6.18-128.1.10.el5 kernel.