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

Eric B Munson
2015-07-22T14:32:26Z

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

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

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