• Muchun Song's avatar
    mm: memcontrol: convert NR_SHMEM_PMDMAPPED account to pages · a1528e21
    Muchun Song authored
    Currently we use struct per_cpu_nodestat to cache the vmstat counters,
    which leads to inaccurate statistics especially THP vmstat counters.  In
    the systems with hundreds of processors it can be GBs of memory.  For
    example, for a 96 CPUs system, the threshold is the maximum number of 125.
    And the per cpu counters can cache 23.4375 GB in total.
    
    The THP page is already a form of batched addition (it will add 512 worth
    of memory in one go) so skipping the batching seems like sensible.
    Although every THP stats update overflows the per-cpu counter, resorting
    to atomic global updates.  But it can make the statistics more accuracy
    for the THP vmstat counters.
    
    So we convert the NR_SHMEM_PMDMAPPED account to pages.  This patch is
    consistent with 8f182270 ("mm/swap.c: flush lru pvecs on compound page
    arrival").  Doing this also can make the unit of vmstat counters more
    unified.  Finally, the unit of the vmstat counters are pages, kB and
    bytes.  The B/KB suffix can tell us that the unit is bytes or kB.  The
    rest which is without suffix are pages.
    
    Link: https://lkml.kernel.org/r/20201228164110.2838-6-songmuchun@bytedance.comSigned-off-by: default avatarMuchun Song <songmuchun@bytedance.com>
    Cc: Alexey Dobriyan <adobriyan@gmail.com>
    Cc: Feng Tang <feng.tang@intel.com>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: Hugh Dickins <hughd@google.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: NeilBrown <neilb@suse.de>
    Cc: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
    Cc: Rafael. J. Wysocki <rafael@kernel.org>
    Cc: Randy Dunlap <rdunlap@infradead.org>
    Cc: Roman Gushchin <guro@fb.com>
    Cc: Sami Tolvanen <samitolvanen@google.com>
    Cc: Shakeel Butt <shakeelb@google.com>
    Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    a1528e21
page_alloc.c 249 KB