[Pkg-xen-devel] Strange behavior when doing xm mem-set Domain-0 (was: Abnormal memory usage of dom0 under Squeeze leading to crash)

[Thomas Goirand]

On 02/03/2011 06:29 PM, Bastian Blank wrote:
> On Thu, Feb 03, 2011 at 05:28:30PM +0800, Thomas Goirand wrote:
>> On 02/03/2011 04:34 PM, Bastian Blank wrote:
>>> Please provide all informations. xm dmesg, the kernel log, xm info.
>> How, if the server reboots when I do it?
> 
> Well, then remove the call and gather the information before breaking
> the system. For anything else, use a serial console.

With the same server, when I put:
GRUB_CMDLINE_XEN_DEFAULT="dom0_mem=512M"
in my /etc/default/grub, the dom0 is fine, running on 501 MB of RAM. If
I don't put this option, then shrink from something like 8 GB (the
server has 12 GB total) to bellow 800, it crashes, with no memory to
release. That's strange, because with 512 MB to the dom0, only 180M is
used, while when I give above 1GB, there's about 800MB of "used RAM",
and it can't be freed.

Any idea why it's ok to boot with 512MB on the dom0, but not ok to
mem-set Domain-0 to it? To me, it seems more a Linux issue than a Xen one...

Thomas