chunk_size "recommended maximum"

[nelsc]

In the first place, it now seems to me that perhaps this parameter should be described as a minimum, not a maximum. If it is treated as a maximum, that might tend to result in oversubscription; if it is treated as a minimum, that would more likely just limit scalability.

In the second place, we should carefully consider whether we can make a statement that makes this stronger than a recommendation; is there any guarantee that might be better?