Re: Adding Memory Overcommitment Manager (MOM) to oVirt

> > 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. Ayal, I definitely agree. I must admit that the project name MOM (while a nice acronym), implies a restricted scope (memory only) but the architecture of MOM does not limit its functionality to memory tuning only. I assert that MOM can easily become the policy engine piece that you are speaking of. The framework is very extensible (a set of Collectors that expose system state, a set of Controllers that expose "tuning knobs", and a policy that reads the state and manipulates the knobs. Adding control for cgroups is as simple as writing a cgroups Collector and Controller.