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Re: [Xen-API] memory hotplug in guest domain (static-max is not so static)

I agree with you and share the same concern because of getting paid for Dynamic memory.

CentOS6 was a disaster to the business model which worked flawless on CentOS5.
CentOS6 started dropping the "Total" memory by few MBs due to this miscalculation in DomU.

The memory restrictions also present outside XAPI like in plain xen we have memmax and DomU cant go beyond that.

I'm not sure how to encourage Xen/Kernel guys to makeÂMemTotal == xc.domain_info['mem_kb'] Âbut if there's a custom way in arch/x86/xen/setup.c e820 MAP then that would be good for the world as newer DomU will show correct "Allocated" memory.

Best of luck with fork !

On Tue, Jun 4, 2013 at 3:59 AM, George Shuklin <george.shuklin@xxxxxxxxx> wrote:
Well, if we start real world talking, main problem is difference in MemTotal computing.

-xen kernels (2.6.18-xen from cenos 5 and forward-porting up to 3.1-xen in SUSE) displaying MemTotal == xc.domain_info['mem_kb']. All pv_ops kernels (f.e. all 3.x vanilla kernels) are using different way to compute MemTotal and showing it lower, than domain memory.

This is really annoying problem for us (we take money for dynamically changed memory). It really hard to explain to angry customer why he pays for 1.1GiB memory and see only 900MiB in 'free' output...

I still in the problem research, but I think it's too hard to debug and fix (because this is not a 'bug', but different model of operating).

The nex problem is xapi restriction on memory limits and whole squeezed opinion about memory management. I think I'll start small fork to see if this possible to change to less enforced.

04.06.2013 01:53, Rushikesh Jadhav ÐÐÑÐÑ:
That seems to be a very good news for CentOS6 ( long awaited )
Congratulations !!

Hope this might work for Windows (hvm instead pv) & other guest os types as well.

I'm pretty bored on making 2.6.32 work with memory balloon & using custom 3.2 sometimes as workaround.
Waiting for RHEL7 & CentOS7 with 3.x kernel ( 3.4 may be ) so the ballooning would work as perfect as RHEL/CentOS5

Not sure about XAPI team but would vote for this feature ;)

On Tue, Jun 4, 2013 at 2:29 AM, George Shuklin <george.shuklin@xxxxxxxxx> wrote:
Good day.

Finally I was able to make memory hotplug working in PV VM under XCP 1.6.

But after VM grow beyond static-max it's no longer possible to migrate it to other host because xapi allocate memory according to current values from squeezed.

Is any ideas about how to solve that problem? I thinking about allowing change static-max value for online virtual machines. Is this fine for xapi team (means: Will that patch accepted?) to allow dynamic changes for static limits?


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