• Michal Hocko's avatar
    mm, thp, proc: report THP eligibility for each vma · 7635d9cb
    Michal Hocko authored
    Userspace falls short when trying to find out whether a specific memory
    range is eligible for THP.  There are usecases that would like to know
    : This is used to identify heap mappings that should be able to fault thp
    : but do not, and they normally point to a low-on-memory or fragmentation
    : issue.
    The only way to deduce this now is to query for hg resp.  nh flags and
    confronting the state with the global setting.  Except that there is also
    PR_SET_THP_DISABLE that might change the picture.  So the final logic is
    not trivial.  Moreover the eligibility of the vma depends on the type of
    VMA as well.  In the past we have supported only anononymous memory VMAs
    but things have changed and shmem based vmas are supported as well these
    days and the query logic gets even more complicated because the
    eligibility depends on the mount option and another global configuration
    Simplify the current state and report the THP eligibility in
    /proc/<pid>/smaps for each existing vma.  Reuse
    transparent_hugepage_enabled for this purpose.  The original
    implementation of this function assumes that the caller knows that the vma
    itself is supported for THP so make the core checks into
    __transparent_hugepage_enabled and use it for existing callers.
    __show_smap just use the new transparent_hugepage_enabled which also
    checks the vma support status (please note that this one has to be out of
    line due to include dependency issues).
    [mhocko@kernel.org: fix oops with NULL ->f_mapping]
      Link: http://lkml.kernel.org/r/20181224185106.GC16738@dhcp22.suse.cz
    Link: http://lkml.kernel.org/r/20181211143641.3503-3-mhocko@kernel.orgSigned-off-by: default avatarMichal Hocko <mhocko@suse.com>
    Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
    Cc: Dan Williams <dan.j.williams@intel.com>
    Cc: David Rientjes <rientjes@google.com>
    Cc: Jan Kara <jack@suse.cz>
    Cc: Mike Rapoport <rppt@linux.ibm.com>
    Cc: Paul Oppenheimer <bepvte@gmail.com>
    Cc: William Kucharski <william.kucharski@oracle.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
huge_memory.c 81.8 KB