Re: [Xen-devel] a ton of kernel issues

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 13/12/11 10:36, George Shuklin wrote:
> On 13.12.2011 14:19, Alessandro Salvatori wrote:
>>
>>> pv_ops is still have some issues with memory limits, but any
>>> new kernel (3.0+) will boot normal and operates with very
>>> minor glitches. Older pv_ops (f.e. debian 2.6.32) have some
>>> more major issues.
>> what glitches should one expect with 3.0+, and having the choice,
>> would it be better to go with 3.1 or even 3.2?
>>
>>
> Right now I know about two of them:
> When you set up memory for virtual machine using xenballon, value in
> dom0 differ from value in domU. The issue is that -xen kernels 'hide'
> some memory in 'used' memory, and pv-ops just reducing TotalMem to value
> without that memory. Practically that means if you set up memory for
> domain to 2GiB client will saw only 1.95GiB and so on.

This really makes no practical difference.  The memory is "used" is
either case and the different reporting is a side-effect of the change
in how certain memory allocations are done.

> The second issue is lack of support of 'pre-inflated balloon', means you
> can not set up memory-static-max to 2GiB, target to 1GiB and do 'memory
> grow' from 1 G to 2 G latter without VM reboot. -xen kernels allow this
> (up to memory-static-max limit).

This should work if memory hotplug is enabled.

It is also supported without memory hotplug but this requires that the
tools supply a suitable memory map that covers the largest
memory-static-max limit you wish to support.  I'm not sure if the tools
can do this yet.

David

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