tree c175aa92b7f7771698052d1b36f52becf21d3c2a
parent 60c5f08e154fd235056645e050f2cd5671b19125
author David Vrabel <david.vrabel@citrix.com> 1313765836 +0100
committer Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> 1314884500 -0400

xen: use maximum reservation to limit amount of usable RAM

Use the domain's maximum reservation to limit the amount of extra RAM
for the memory balloon. This reduces the size of the pages tables and
the amount of reserved low memory (which defaults to about 1/32 of the
total RAM).

On a system with 8 GiB of RAM with the domain limited to 1 GiB the
kernel reports:

Before:

Memory: 627792k/4472000k available

After:

Memory: 549740k/11132224k available

A increase of about 76 MiB (~1.5% of the unused 7 GiB).  The reserved
low memory is also reduced from 253 MiB to 32 MiB.  The total
additional usable RAM is 329 MiB.

For dom0, this requires at patch to Xen ('x86: use 'dom0_mem' to limit
the number of pages for dom0') (c/s 23790)

CC: stable@kernel.org
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>