----- Original Message -----
> Hi all,
> Very shortly Mark will be sending some patches for review that
> implement the
> long-awaited integration of mom with vdsm.  I felt it would be easier
> to
> understand the changes to vdsm if they were explained a bit better.
>  In support
> of this I have created a wiki page on ovirt.org with a diagram:
> http://ovirt.org/wiki/Features/MomIntegration
> To facilitate discussion, here is the text of that page:
> As discussed at the oVirt Workshop and elsewhere, integrating mom
> with vdsm will
> benefit oVirt by providing a mechanism for dynamic, policy-based
> tuning.  This
> mechanism will pave the way for implementing memory ballooning
> policies, can
> enhance migration policy, and will replace the existing ksm tuning
> thread.
> MOM exists today as an independent library that can be used by python
> programs
> such as vdsm or in standalone mode (by using the accompanying momd
> program.
> Mom's operation is very configurable.  The management policy is
> written in a
> Fortran-like language and is replaceable by the end user.
>  Additionally, plugins
> allow you to customize the types of information collected and the
> manner in
> which it is collected.  Similarly, Controller plugins permit a
> completely
> flexible control API to be created.
> To integrate mom, vdsm will initialize the mom library in a new
> thread and start
> it.  Therefore, mom and vdsm will exist in the same process.  Vdsm
> will
> configure the mom instance to use plugins and a policy that
> exclusively target
> the vdsm API.  All statistics collection will occur via API calls and
> any
> management actions (including adjustments to KSM and VM balloons)
> will be done
> through the vdsm api as well.  Mom will not use libvirt at all (not
> even to
> monitor for new VMs on the system).
> Packaging logistics:
> -------------------------
> Mom is an independent package that is already in Fedora.  Any changes
> to mom
> that are required to support this integration will be submitted to
> the mom
> project for inclusion.  Vdsm will consume the standard MOM package as
> a python
> module/library.
> In order to control its mom instance, vdsm will ship a mom
> configuration file
> and a mom policy file that will set mom's default behavior.  At
> startup, vdsmd
> will import mom and initialize it with the configuration and policy
> files.  From
> that point on, mom will interact with vdsm through the well-defined
> API in
> API.py.
> New features needed in vdsm:
> ---------------------------------------
> In order to fully benefit from mom's capabilities, vdsm should
> implement the
> following extra features/APIs:
> - Collection of more memory statistics via ovirt-guest-agent
> including the
>   current memory balloon value.
> - A vmBalloon API to set a new balloon target.

Looks good to me.

> --
> Adam Litke <a...@us.ibm.com>
> IBM Linux Technology Center
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