Re: Adding Memory Overcommitment Manager (MOM) to oVirt
----- Original Message -----
On 09/26/2011 04:26 PM, Anthony Liguori wrote:
> On 09/26/2011 03:19 PM, Dor Laor wrote:
>> On 09/26/2011 11:01 PM, Adam Litke wrote:
>>> Hi all,
>>>
>>> I would like propose adding the Memory Overcommitment Manager
>>> (MOM)
>>> project to
>>> oVirt. MOM is a daemon that is used to apply dynamic host-level
>>> and
>>> VM-level
>>> tuning according to a customizable policy. Today MOM can control
>>> memory
>>> ballooning and KSM. Please see the following links for more
>>> information:
>>>
>>> Project wiki:
>>> http://github.com/aglitke/mom/wiki
>>>
>>> Source code:
>>> git://github.com/aglitke/mom.git
>>>
>>> KVM Forum presentation and video:
>>> http://www.linux-kvm.org/wiki/images/e/e8/2010-forum-litke-kvmforum2010.pdf
>>>
>>> http://vimeo.com/15223652
>>>
>>> developerWorks article:
>>> http://www.ibm.com/developerworks/linux/library/l-overcommit-kvm-resources/
>>>
>>>
>>> In my view, MOM could be nicely integrated with oVirt-node and
>>> VDSM.
>>> I am
>>> looking forward to your comments and am ready to address some
>>> next
>>> steps.
>>>
>>> Thanks!
>>>
>>
>> +1 for mom, hope to see a dad too :)
>
> Data Acceleration Director?
>
> Joking aside, would MOM just be integrated directly into VDSM or
> would
> it remain as a separate project?
>
> I can envision a world where MOM is just a feature of VDSM.
The key question is how do we integrate it into the stack,
- is it integrated into WDSM as Anthony mentions
- or is a project that WDSM uses to provide MOM
- etc.
First of all I think this is great! Thanks Adam!
Wrt the question above, the way I see vdsm going forward is a lot more policy management,
especially once we start talking about SLAs. This will involve a lot more than just memory
policies, and although I may be impartial here, I think that this should fall under vdsm
or under a policy engine project (bigger scope than just memory) which vdsm would use.
To elaborate, in addition to memory, we need to manage policies around network, storage
and cpu and manipulate cgroups, tc, page cache etc. If we take page cache as an example,
it affects memory on the machine hence, MOM would like to tweak it (also in the preso),
but we already have recent results from the perf team to change the defaults here to
significantly increase I/O throughput, improve fairness and reduce effect of buffered
writers on VMs and we know that going forward we'll have to tweak these parameters
dynamically to adjust to varying workloads, esp if we ever plan on making good the claim
for a hybrid server. Having separate projects tweaking the same params will not lead to
good results.
Carl.
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