Re: [Xen-users] Memory allocation with Xen

[Shiazy Fuzzy <shiazy@xxxxxxxxx>]

On Fri, Mar 25, 2016 at 11:08 AM, Zhang, Chunyu <zhangcy@xxxxxxxxxxxxxx> wrote:

Populate on Demand + balloon , see :

https://blog.xenproject.org/2014/02/14/ballooning-rebooting-and-the-feature-youve-never-heard-of/

So, if I understand, support for memory hotplug is present but is not compiled by default, is it?

I say this because the kernel 3.10 already contains the hotplug patch proposed by Daniel Kiper (https://lkml.org/lkml/2011/3/28/108).

See ./drivers/xen/balloon.c in the linux kernel source (lines between the CONFIG_XEN_BALLOON_MEMORY_HOTPLUG macro).

Cheers,

S.

 

>Hello,
>
>I'm using Xen 4.4.3 under Fedora 21 (kernel 4.1.13 x86_64).
>
>All my virtual machines run CentOS 7 (kernel 3.10 x86_64) as HVM and start with overcommitted memory:
>  builder="hvm"
>  maxmem=8192
>  memory=6144
>
>I would like to know what techniques Xen uses to change the memory allocation of a virtual machine, when I run commands like these:
>
>Memory decrease:
>$ xl mem-set foo 4096m
>
>Memory increase:
>
>$ xl mem-set foo 7168m
>
>On the Web, I found different posts talking about techniques like memory ballooning and memory hotplug.
>But I don't understand what techniques my version of Xen actually uses, since some posts are very outdated and other seems related to unstable versions of Xen.
>
>How can I find it out?
>
>
>Thank you very much for your help.
>
>
>Best,
>
>S.

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