• Kirill A. Shutemov's avatar
    mm: consolidate page table accounting · af5b0f6a
    Kirill A. Shutemov authored
    Currently, we account page tables separately for each page table level,
    but that's redundant -- we only make use of total memory allocated to
    page tables for oom_badness calculation.  We also provide the
    information to userspace, but it has dubious value there too.
    
    This patch switches page table accounting to single counter.
    
    mm->pgtables_bytes is now used to account all page table levels.  We use
    bytes, because page table size for different levels of page table tree
    may be different.
    
    The change has user-visible effect: we don't have VmPMD and VmPUD
    reported in /proc/[pid]/status.  Not sure if anybody uses them.  (As
    alternative, we can always report 0 kB for them.)
    
    OOM-killer report is also slightly changed: we now report pgtables_bytes
    instead of nr_ptes, nr_pmd, nr_puds.
    
    Apart from reducing number of counters per-mm, the benefit is that we
    now calculate oom_badness() more correctly for machines which have
    different size of page tables depending on level or where page tables
    are less than a page in size.
    
    The only downside can be debuggability because we do not know which page
    table level could leak.  But I do not remember many bugs that would be
    caught by separate counters so I wouldn't lose sleep over this.
    
    [[email protected]: fix mm/huge_memory.c]
    Link: http://lkml.kernel.org/r/[email protected]Signed-off-by: default avatarKirill A. Shutemov <[email protected]>
    Acked-by: default avatarMichal Hocko <[email protected]>
    [[email protected]: fix build]
      Link: http://lkml.kernel.org/r/[email protected]Signed-off-by: default avatarAndrew Morton <[email protected]>
    Signed-off-by: default avatarLinus Torvalds <[email protected]>
    af5b0f6a
proc.txt 88.3 KB