memory_limit(size = NA)
NA report the memory size, otherwise request
a new limit, in MiB.This function is used to manage the total memory allocation
for the current session and for child processes. On POSIX
systems, the getrlimit64(2) and setrlimit64(2) APIs
with resource RLIMIT_AS are used.
Support for Windows might become available in the future; in the meantime,
use utils::memory.limit.