• Michal Hocko's avatar
    mm, memory_hotplug: remove zone restrictions · c6f03e29
    Michal Hocko authored
    Historically we have enforced that any kernel zone (e.g ZONE_NORMAL) has
    to precede the Movable zone in the physical memory range.  The purpose
    of the movable zone is, however, not bound to any physical memory
    restriction.  It merely defines a class of migrateable and reclaimable
    memory.
    
    There are users (e.g.  CMA) who might want to reserve specific physical
    memory ranges for their own purpose.  Moreover our pfn walkers have to
    be prepared for zones overlapping in the physical range already because
    we do support interleaving NUMA nodes and therefore zones can interleave
    as well.  This means we can allow each memory block to be associated
    with a different zone.
    
    Loosen the current onlining semantic and allow explicit onlining type on
    any memblock.  That means that online_{kernel,movable} will be allowed
    regardless of the physical address of the memblock as long as it is
    offline of course.  This might result in moveble zone overlapping with
    other kernel zones.  Default onlining then becomes a bit tricky but
    still sensible.  echo online > memoryXY/state will online the given
    block to
    
    	1) the default zone if the given range is outside of any zone
    	2) the enclosing zone if such a zone doesn't interleave with
    	   any other zone
            3) the default zone if more zones interleave for this range
    
    where default zone is movable zone only if movable_node is enabled
    otherwise it is a kernel zone.
    
    Here is an example of the semantic with (movable_node is not present but
    it work in an analogous way). We start with following memblocks, all of
    them offline:
    
      memory34/valid_zones:Normal Movable
      memory35/valid_zones:Normal Movable
      memory36/valid_zones:Normal Movable
      memory37/valid_zones:Normal Movable
      memory38/valid_zones:Normal Movable
      memory39/valid_zones:Normal Movable
      memory40/valid_zones:Normal Movable
      memory41/valid_zones:Normal Movable
    
    Now, we online block 34 in default mode and block 37 as movable
    
      root@test1:/sys/devices/system/node/node1# echo online > memory34/state
      root@test1:/sys/devices/system/node/node1# echo online_movable > memory37/state
      memory34/valid_zones:Normal
      memory35/valid_zones:Normal Movable
      memory36/valid_zones:Normal Movable
      memory37/valid_zones:Movable
      memory38/valid_zones:Normal Movable
      memory39/valid_zones:Normal Movable
      memory40/valid_zones:Normal Movable
      memory41/valid_zones:Normal Movable
    
    As we can see all other blocks can still be onlined both into Normal and
    Movable zones and the Normal is default because the Movable zone spans
    only block37 now.
    
      root@test1:/sys/devices/system/node/node1# echo online_movable > memory41/state
      memory34/valid_zones:Normal
      memory35/valid_zones:Normal Movable
      memory36/valid_zones:Normal Movable
      memory37/valid_zones:Movable
      memory38/valid_zones:Movable Normal
      memory39/valid_zones:Movable Normal
      memory40/valid_zones:Movable Normal
      memory41/valid_zones:Movable
    
    Now the default zone for blocks 37-41 has changed because movable zone
    spans that range.
    
      root@test1:/sys/devices/system/node/node1# echo online_kernel > memory39/state
      memory34/valid_zones:Normal
      memory35/valid_zones:Normal Movable
      memory36/valid_zones:Normal Movable
      memory37/valid_zones:Movable
      memory38/valid_zones:Normal Movable
      memory39/valid_zones:Normal
      memory40/valid_zones:Movable Normal
      memory41/valid_zones:Movable
    
    Note that the block 39 now belongs to the zone Normal and so block38
    falls into Normal by default as well.
    
    For completness
    
      root@test1:/sys/devices/system/node/node1# for i in memory[34]?
      do
    	echo online > $i/state 2>/dev/null
      done
    
      memory34/valid_zones:Normal
      memory35/valid_zones:Normal
      memory36/valid_zones:Normal
      memory37/valid_zones:Movable
      memory38/valid_zones:Normal
      memory39/valid_zones:Normal
      memory40/valid_zones:Movable
      memory41/valid_zones:Movable
    
    Implementation wise the change is quite straightforward.  We can get rid
    of allow_online_pfn_range altogether.  online_pages allows only offline
    nodes already.  The original default_zone_for_pfn will become
    default_kernel_zone_for_pfn.  New default_zone_for_pfn implements the
    above semantic.  zone_for_pfn_range is slightly reorganized to implement
    kernel and movable online type explicitly and MMOP_ONLINE_KEEP becomes a
    catch all default behavior.
    
    Link: http://lkml.kernel.org/r/20170714121233.16861-3-mhocko@kernel.org
    
    Signed-off-by: default avatarMichal Hocko <mhocko@suse.com>
    Acked-by: default avatarJoonsoo Kim <iamjoonsoo.kim@lge.com>
    Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
    Acked-by: default avatarReza Arbab <arbab@linux.vnet.ibm.com>
    Cc: Mel Gorman <mgorman@suse.de>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Yasuaki Ishimatsu <yasu.isimatu@gmail.com>
    Cc: Xishi Qiu <qiuxishi@huawei.com>
    Cc: Kani Toshimitsu <toshi.kani@hpe.com>
    Cc: <slaoub@gmail.com>
    Cc: Daniel Kiper <daniel.kiper@oracle.com>
    Cc: Igor Mammedov <imammedo@redhat.com>
    Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
    Cc: Wei Yang <richard.weiyang@gmail.com>
    Cc: <linux-api@vger.kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    c6f03e29
memory.c 20.2 KB