• Eric B Munson's avatar
    mm: introduce VM_LOCKONFAULT · de60f5f1
    Eric B Munson authored
    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.
    
    For the example of a large file, this is the usage pattern for a large
    statical language model (probably applies to other statical or graphical
    models as well).  For the security example, any application transacting in
    data that cannot be swapped out (credit card data, medical records, etc).
    
    This patch introduces the ability to request that pages are not
    pre-faulted, but are placed on the unevictable LRU when they are finally
    faulted in.  The VM_LOCKONFAULT flag will be used together with VM_LOCKED
    and has no effect when set without VM_LOCKED.  Setting the VM_LOCKONFAULT
    flag for a VMA will cause pages faulted into that VMA to be added to the
    unevictable LRU when they are faulted or if they are already present, but
    will not cause any missing pages to be faulted in.
    
    Exposing this new lock state means that we cannot overload the meaning of
    the FOLL_POPULATE flag any longer.  Prior to this patch it was used to
    mean that the VMA for a fault was locked.  This means we need the new
    FOLL_MLOCK flag to communicate the locked state of a VMA.  FOLL_POPULATE
    will now only control if the VMA should be populated and in the case of
    VM_LOCKONFAULT, it will not be set.
    Signed-off-by: 's avatarEric B Munson <emunson@akamai.com>
    Acked-by: 's avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Acked-by: 's avatarVlastimil Babka <vbabka@suse.cz>
    Cc: Michal Hocko <mhocko@suse.cz>
    Cc: Jonathan Corbet <corbet@lwn.net>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Geert Uytterhoeven <geert@linux-m68k.org>
    Cc: Guenter Roeck <linux@roeck-us.net>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: Michael Kerrisk <mtk.manpages@gmail.com>
    Cc: Ralf Baechle <ralf@linux-mips.org>
    Cc: Shuah Khan <shuahkh@osg.samsung.com>
    Cc: Stephen Rothwell <sfr@canb.auug.org.au>
    Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
    de60f5f1
mlock.c 19.9 KB