Re: [Xen-users] understanding memory hot-plug in a paravitual domU

[Jordi Moles Blanco <jordi@xxxxxxxxx>]

Hi,

George, thanks for that information as well.

It's good to know that this feature is in the roadmap.

I'm also working on resezing disk partitions without having to reboot 
the domU. It works for 3.X kernels pretty much "out of the box". The 
problem, though, is that running a debian wheeze dom0 with kernel 3.X 
and xen 4.1 is a bit unstable to me. I've run some stress tests under 
those software versions and came across some problems that i had never 
seen. Anyway, if kernel 3.1 comes with memory hotplug i think I'll have 
to switch to get all these improvements: memory hotplug, hot disk 
resize, new xl scripts, etc.
thanks.


Al 18/11/11 13:05, En/na George Shuklin ha escrit:
> AFAIK there is two different operational mode. When we running classic 
> old kernels we using just ballooning. And newer kernel (3.1, 3.2) 
> supports for memory-hotplug which allow to grow domU memory beyond 
> initial memory.
> Unfortunately I was not succeed at making memory-hotplug works. Sad.
>
> But some older -xen kernel allow little trick - domain starts with 
> 'pre-inflated' balloon, allowing (not really, but looking like) grow 
> at values higher then initial memory in domU.
> On 18.11.2011 15:42, Jordi Moles Blanco wrote:
> > Hi,
> >
> > thanks Kyle for the information.
> >
> > I had read a lot of documentation and posts in forums and somehow 
> > missed that.
> > As you say, I feel that people would be less confused with this if 
> > mem-max clearly said that you can't grow the balloon higher than the 
> > initial memory value.
> > Thanks.
> >
> >
> >
> > Al 18/11/11 11:47, En/na Kyle Lexmond ha escrit:
> > > Hi,
> > > Everything that I've read said that you can't balloon the memory
> > > beyond the maximum you specified in the config file when you created
> > > the domain. (eg.
> > > http://www.centos.org/docs/5/html/Virtualization-en-US/virt-task-xm-create-manage-doms.html#id2645186) 
> > >
> > > So, no, based on the docs, the behaviour that you're seeing is
> > > expected, and, no, you can't balloon higher than the initial memory
> > > value.
> > >
> > > Strange that xm mem-max isn't giving errors though.
> > >
> > > ...
> > > > **********
> > > > # xm mem-max server 4096
> > > > # xm mem-set server 4096
> > > > **********
> > > >
> > > >
> > > > can i suppose then that this should work?
> > > >
> > > > the thing is that xen doesn't complain, but both 'xen top' and the 
> > > > machine
> > > > itself don't seem to show any increase in the memory.
> > > >
> > > > However, it works when setting a lower value.
> > > >
> > > > For example, I can create 'server' with 2048 and then go down to 
> > > > 1024 and
> > > > then to 2048 again, but never to a higher value. So... i guess that
> > > > mem-hotplug works because I can go down and up, but It can never go up
> > > > higher than the initial memory value.
> > > >
> > > > that's why yesterday I was asking if that's is even possible,
>
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Jordi Moles Blanco
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