Re: [PATCH V4 5/6] mm: mmap: Add mmap flag to request VM_LOCKONFAULT

On Wed, 22 Jul 2015, Kirill A. Shutemov wrote:

On Tue, Jul 21, 2015 at 03:59:40PM -0400, Eric B Munson wrote:

quoted

The cost of faulting in all memory to be locked can be very high when
working with large mappings.  If only portions of the mapping will be
used this can incur a high penalty for locking.

Now that we have the new VMA flag for the locked but not present state,
expose it as an mmap option like MAP_LOCKED -> VM_LOCKED.

What is advantage over mmap() + mlock(MLOCK_ONFAULT)?

There isn't one, it was added to maintain parity with the
mlock(MLOCK_LOCK) -> mmap(MAP_LOCKED) set.  I think not having will lead
to confusion because we have MAP_LOCKED so why don't we support
LOCKONFAULT from mmap as well.