NativeMemory.AlignedAlloc() page boundary alignment

[samuel-lucas6]

Hi, I'd like to double check whether NativeMemory.AlignedAlloc() with alignment: Environment.SystemPageSize will properly align with a page/allocate memory at the beginning of a page boundary. My use case is memory locking on different OSes, like with VirtualLock. Many thanks.

[huoyaoyuan]

The guarantee is provided by underlying system call, for example _aligned_alloc on Windows.

However, when working with other system calls, consider to be explicit about the syscall usages, to ensure any other implications are met.

[samuel-lucas6]

But does _aligned_alloc provide this guarantee? From what I read, it sounds like it doesn't.

[MichalPetryka]

AFAIR malloc and the family can return memory which is a part of a large page, there this assumption would AFAIR not be valid since your data would just be a part of it.
Additionally, relying on this will be problematic too even without large pages when it comes to freeing as you'd need to restore the original memory state before doing so.

[samuel-lucas6]

Yes, that was my concern. It's unfortunately not documented very clearly. I'm guessing there's no way of doing this using APIs from the standard library.