On Thu, Dec 01, 2011 at 11:05:55AM +0200, Dor Laor wrote:
> On 11/29/2011 06:29 PM, Adam Litke wrote:
> > After discussing MOM / VDSM integration at length, two different strategies 
> > have
> > emerged.  I will call them Plan A and Plan B:
> >
> > Plan A: MOM integration at the OS/Packaging level
> > Plan B: MOM integration as a new VDSM thread
> 
> I think a form of plan B is more appropriate:
> 
> In general we can look at MOM vs VDSM just like micro kernel vs linux 
> kernel approach. MOM can be independent project but then it will need to 
> expose much more apis for VDSM and wise verse.
> 
> For example, take live migration, there is no point of MOM balloon a 
> guest while it is migrating. So either you ignore that which is bad or 
> now need to listen to VDSM events on VM migration.
> 
> Think about hot plug vcpu/pci-device to a VM - if before MOM used some 
> SLA for the VM, now it will need to change to cope w/ the new resources, 
> again more api/events for that.
> 
> Another thing - all of the settings for per VM KSM/THP/Swap/Balloon - 
> all will need to propagate from the vdsm api towards MOM.

Indeed, disagreement is much more interesting! I think that the information
that Vdsm is expected to provide to momd is quite limitted and slowly-changing.
We may be better off defining an API for Vdsm to notify momd of VM state
changes, than to entangle mom within Vdsm.

Dan.
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