"Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> writes: > On x86, 5-level paging enables 56-bit userspace virtual address space. > Not all user space is ready to handle wide addresses. It's known that > at least some JIT compilers use higher bits in pointers to encode their > information. It collides with valid pointers with 5-level paging and > leads to crashes. > > To mitigate this, we are not going to allocate virtual address space > above 47-bit by default. > > But userspace can ask for allocation from full address space by > specifying hint address (with or without MAP_FIXED) above 47-bits. > > If hint address set above 47-bit, but MAP_FIXED is not specified, we try > to look for unmapped area by specified address. If it's already > occupied, we look for unmapped area in *full* address space, rather than > from 47-bit window. > > This approach helps to easily make application's memory allocator aware > about large address space without manually tracking allocated virtual > address space. > So if I have done a successful mmap which returned > 128TB what should a following mmap(0,...) return ? Should that now search the *full* address space or below 128TB ? -aneesh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
