[Pacemaker] Resource capacity limit

[Lars Marowsky-Bree]

On 2009-11-13T15:23:20, Yan Gao <ygao at novell.com> wrote:

> Minimal:
> Consider the utilization of nodes and resources. While if a resource has
> the same score for several available nodes, do _not_ balance the load.
> That implies that the resources  will be concentrated to minimal number of nodes.
> 
> Balanced:
> Consider the utilization of nodes and resources. If a resource has
> the same score for several available nodes:
> * First, balance the load according to the remaining capacity of nodes.
> (implemented from compare_capacity())
> * If the nodes still have the equal remaining capacity, then balance
> the load according to the numbers of resources that the nodes will run.
> 
> The strategies are determined mainly from sort_node_weight(), so I changed the
> prototypes of some functions a bit.

Hi Yan Gao,

great work!

But Minimal or Balanced don't quite do what is described above. A linear
assignment doesn't provide anything close to an optimal solution, in
particular if combined with (anti-)collocation rules; solving this
optimally is NP-complete (rucksack problem for the Minimal policy, for
example), though heuristics to get close in sane time exists.

At least this is worth understanding and describing as a limitation of
the current algorithm.


Regards,
    Lars

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