• Anshuman Khandual's avatar
    mm/hugetlb: distinguish between migratability and movability · 7ed2c31d
    Anshuman Khandual authored
    Patch series "arm64/mm: Enable HugeTLB migration", v4.
    
    This patch series enables HugeTLB migration support for all supported
    huge page sizes at all levels including contiguous bit implementation.
    Following HugeTLB migration support matrix has been enabled with this
    patch series.  All permutations have been tested except for the 16GB.
    
               CONT PTE    PMD    CONT PMD    PUD
               --------    ---    --------    ---
      4K:         64K     2M         32M     1G
      16K:         2M    32M          1G
      64K:         2M   512M         16G
    
    First the series adds migration support for PUD based huge pages.  It
    then adds a platform specific hook to query an architecture if a given
    huge page size is supported for migration while also providing a default
    fallback option preserving the existing semantics which just checks for
    (PMD|PUD|PGDIR)_SHIFT macros.  The last two patches enables HugeTLB
    migration on arm64 and subscribe to this new platform specific hook by
    defining an override.
    
    The second patch differentiates between movability and migratability
    aspects of huge pages and implements hugepage_movable_supported() which
    can then be used during allocation to decide whether to place the huge
    page in movable zone or not.
    
    This patch (of 5):
    
    During huge page allocation it's migratability is checked to determine
    if it should be placed under movable zones with GFP_HIGHUSER_MOVABLE.
    But the movability aspect of the huge page could depend on other factors
    than just migratability.  Movability in itself is a distinct property
    which should not be tied with migratability alone.
    
    This differentiates these two and implements an enhanced movability check
    which also considers huge page size to determine if it is feasible to be
    placed under a movable zone.  At present it just checks for gigantic pages
    but going forward it can incorporate other enhanced checks.
    
    Link: http://lkml.kernel.org/r/1545121450-1663-2-git-send-email-anshuman.khandual@arm.com
    
    Signed-off-by: default avatarAnshuman Khandual <anshuman.khandual@arm.com>
    Reviewed-by: default avatarSteve Capper <steve.capper@arm.com>
    Reviewed-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
    Suggested-by: default avatarMichal Hocko <mhocko@kernel.org>
    Acked-by: default avatarMichal Hocko <mhocko@suse.com>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    7ed2c31d
hugetlb.h 18.2 KB