从内存中删除不需要的数据

Question

我有一个加载8 GB数据然后返回6 MB数据（列表）的函数。 但后来我启动了基于多进程的函数，整个8 GB被传递给所有进程，因为我只需要函数返回的6 MB。因此，内存使用量为8 * process_count。如何删除价值8 GB的不需要的数据。

伪代码：

def fun():
    uses another function to load a big json file and get keys from it.     
 something like this:
 return [k for k,v in ext function returning a big dictionary created from big json file]

def main():
    list_ll = copy.deepcopy(fun()) # done to remove reference to fun
    gc.collect()
    launch multiprocess functions each of which takes a part of list.
    All 8 GB data is being copied.Memory usage too high.