Minimum amount of free space after trimming or shifting the stack.
Setting this value higher can reduce the number of garbage collections
and stack-shifts at the cost of higher memory usage. The amount is
reported and specified in cells. A cell is 4 bytes in the
32-bit version and 8 bytes on the 64-bit version. See
See also trim_stacks/0
These two figures determine whether, if the stacks are low, a stack
shift (expansion) or garbage collection is performed. This
depends on these two parameters, the current stack usage and the amount
of stack used after the last garbage collection. A garbage collection is
started if used > factor × lastused + low.
All stacks trigger overflow before actually reaching the limit, so the
resulting error can be handled gracefully. The spare stack is used for
from the garbage collector and for handling exceptions. The default
suffices, unless the user redefines related hooks. Do
not specify large values for this because it reduces the amount
of memory available for your real task.