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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2011-12-13 at 13:17 +0000, David Vrabel wrote:
> 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.

With xl this should work using the "maxmem" option. (xm probably uses
the same name)

Ian.

> 
> David
> 
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