Once you map a file in memory, you cannot increase its size. This is a known limitation of memory mapped files. …you must calculate or estimate the size of the finished file because file mapping objects are static in size; once created, their size cannot be increased or decreased. One strategy would be to use … Read more
The correct terms are memory mapped files and anonymous mappings. When referring to memory mapping, one is usually referring to mmap(2). There are 2 categories for using mmap. One category is SHARED vs PRIVATE mappings. The other category is FILE vs ANONYMOUS mappings. Mixed together you get the 4 following combinations: PRIVATE FILE MAPPING SHARED … Read more
Memory-mapped files copy data from disk into memory a page at a time. Unused pages are free to be swapped out, the same as any other virtual memory, unless they have been wired into physical memory using mlock(2). Memory mapping leaves the determination of what to copy from disk to memory and when to the … Read more
Memory-mapped files are beneficial for scenarios where a relatively small portion (view) of a considerably larger file needs to be accessed repeatedly. In this scenario, the operating system can help optimize the overall memory usage and paging behavior of the application by paging in and out only the most recently used portions of the mapped … Read more
Following static method could be used: public static void unmap(MappedByteBuffer buffer) { sun.misc.Cleaner cleaner = ((DirectBuffer) buffer).cleaner(); cleaner.clean(); } But this is unsafe solution because of following: 1) Lead to failures if someone use MappedByteBuffer after unmap 2) It relies on MappedByteBuffer implementation details