snappyHexMesh spends excessive time balancing during refinement

Functionality to add/problem to solve

snappyHexMesh balances mesh before or after each refinement step. For large numbers of cores (e.g. 8000) balancing can be expensive.

Target audience

snappyHexMesh on large numbers of cores.

Proposal

Not do balancing until a reasonable number of cells per processor has been reached.

What does success look like, and how can we measure that?

Speedup.