Bug#595711: linux-image-2.6.26-2-xen-686: Wrong free memory values for xen kernel with xenballoon use

[George Shuklin <amarao@desunote.ru>]

Package: linux-image-2.6.26-2-xen-686
Severity: important

I belive current version of xen (as domU) kernel for debian report free memory wrong: system reports lots of free memory, but acutally all memory is used up. 

Condition to reproduce:

Xen evnironment, maxmem is very large (10-20GiB memory), mem relativly low (800-900MiB).

Booted domU reports about 500MiB free, but if we try to use it, we will get swap (or oom/MemoryError is swap disabled) right after about 120MiB.

I test this behavior in newer gentoo/SUSE kernel and they in same condition show that about 750MiB is used (this match experemental data).

I belive, this somehow related to difference in drivers/xen/balloon.c, gentoo/SUSE version have some lines like 

        totalram_pages--;
(in balloon_append() function)

and 
      totalram_pages++;
(in balloon_retrieve() function)

Those lines are in Gentoo kernel  (linux-2.6.34-xen) but absent in Debian (linux-image-2.6.26-2-xen-686)

-- System Information:
Debian Release: squeeze/sid
  APT prefers unstable
  APT policy: (990, 'unstable'), (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 2.6.32-5-amd64 (SMP w/4 CPU cores)
Locale: LANG=ru_RU.utf8, LC_CTYPE=ru_RU.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash