Although the memory allocated will not be freed back to the system, before the program exit, unless using things like mmap, but the memory allocated will be recycled for the same program.

The real concern, under this context, is not the amount of memory your program used, but whether the amount of memory it used seems reasonable to you. If yes, fine; if not there is a memory leak.

Also how active and sensitive the garbage collector is, is an extremely important fact here. If it is not active and sensitive enough, it would intend to allocate more memory than needed, as from time to time, it will fail to realize that there is actually allocated but freed memory or should be freed available.