释放锁定的内存是否可以解锁相应的页面？

Question

It's clear how you can combine mlockall() and malloc() to lock all the pages allocated by a process during its life. What is not clear to me by reading the documentation is whether freeing already locked memory implies an automatic unlock of the corresponding pages.

Answer 1

If free returns the memory to the system (ie it was allocated with mmap and will be freed with munmap ), then the lock will automatically be removed when it is unmapped. This is typically the case with large allocations.

If free returns the memory to a heap managed within the process, then the lock will remain. This is typically the case for small allocations.

On GNU/Linux, you can use mallopt to get and set the threshold for allocations using mmap ; the default (on my computer, at least) is 128kb. On other Unix flavours, you might need to use mmap directly if you need that level of control.