Re: page migration: Fail with error if swap not setup

Christoph Lameter
2006-03-15T19:00:31Z

On Wed, 15 Mar 2006, Marcelo Tosatti wrote:

> > That does not answer the question if VM_LOCKED pages should be
> > migratable. We all agree that they should not show up on swap.
>
> I guess you missed the first part of the man page:
>
> All pages which contain a part of the specified memory range are
> guaranteed be resident in RAM when the mlock system call returns
> successfully and they are guaranteed to stay in RAM until the pages are
> unlocked by munlock or munlockall, until the pages are unmapped via
> munmap, or until the process terminates or starts another program with
> exec. Child processes do not inherit page locks across a fork.
>
> That is, mlock() only guarantees that pages are kept in RAM and not
> swapped. It does seem to refer to physical placing of pages.

If VM_LOCKED is not pinning memory then how does one pin memory? There are
likely applications / drivers that require memory not to move. Increase
pagecount?