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On Wed, Jul 17, 2013 at 8:28 PM, Christian Schröder <cs@xxxxxxxxx> wrote:

Hi list,
I try to understand memory ballooning. I have a xen server (kernel 2.6.27.54-0.2-xen) with 32 gb total memory. A domU has been started with "memory=4096" and "maxmem=8192". This is the status of the balloon driver in the domU:

What is the guest kernel & os type ?

test:~ # cat /proc/xen/balloon
Current allocation: 4194304 kB
Requested target: 4194304 kB
Minimum target: 565248 kB
Maximum target: 8388608 kB
Low-mem balloon: 4194304 kB
High-mem balloon: 0 kB
Driver pages: 0 kB

I then try to increase the memory of this domU using the following command: "xm mem-set test 8192". However, the memory only increases to about 5 gb. This is what the balloon driver says:

test:~ # cat /proc/xen/balloon
Current allocation: 5281180 kB
Requested target: 8388608 kB
Minimum target: 565248 kB
Maximum target: 8388608 kB
Low-mem balloon: 3107428 kB
High-mem balloon: 0 kB
Driver pages: 0 kB

Can anybody explain why the current allocation is less than the requested target? "free" reports the same size:

test:~ # free -k
total used free shared buffers cached
Mem: 5281180 2478960 2802220 0 768 584432
-/+ buffers/cache: 1893760 3387420
Swap: 2096444 0 2096444

What can I do to make the full 8 gb usable to the domU?

Kind regards,
Christian

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Re: [Xen-users] Understanding memory ballooning