Returns: The options that control the pooling behavior of this resource.
The values in the returned struct may differ
from those supplied to the pool resource constructor in that
values of zero will be replaced with implementation-defined
defaults, and sizes may be rounded to unspecified granularity.
Effects: If the pool selected for a block of size bytes
is unable to satisfy the memory request from its own internal data structures,
it will call upstream_resource()->allocate() to obtain more memory.
If bytes is larger than that which the largest pool can handle,
then memory will be allocated using upstream_resource()->allocate().