On Tue,  7 Jul 2015 13:03:38 -0400 Eric B Munson [off-list ref] wrote:

mlock() allows a user to control page out of program memory, but this
comes at the cost of faulting in the entire mapping when it is
allocated.  For large mappings where the entire area is not necessary
this is not ideal.  Instead of forcing all locked pages to be present
when they are allocated, this set creates a middle ground.  Pages are
marked to be placed on the unevictable LRU (locked) when they are first
used, but they are not faulted in by the mlock call.

This series introduces a new mlock() system call that takes a flags
argument along with the start address and size.  This flags argument
gives the caller the ability to request memory be locked in the
traditional way, or to be locked after the page is faulted in.  New
calls are added for munlock() and munlockall() which give the called a
way to specify which flags are supposed to be cleared.  A new MCL flag
is added to mirror the lock on fault behavior from mlock() in
mlockall().  Finally, a flag for mmap() is added that allows a user to
specify that the covered are should not be paged out, but only after the
memory has been used the first time.

Thanks for sticking with this.  Adding new syscalls is a bit of a
hassle but I do think we end up with a better interface - the existing
mlock/munlock/mlockall interfaces just aren't appropriate for these
things.

I don't know whether these syscalls should be documented via new
manpages, or if we should instead add them to the existing
mlock/munlock/mlockall manpages.  Michael, could you please advise?