[PATCH 0/5] memory-hotplug: suitable memory should go to ZONE_MOVABLE

[Wang Nan]

This series of patches fix a problem when adding memory in bad manner.
For example: for a x86_64 machine booted with "mem=400M" and with 2GiB
memory installed, following commands cause problem:

 # echo 0x40000000 > /sys/devices/system/memory/probe
[   28.613895] init_memory_mapping: [mem 0x40000000-0x47ffffff]
 # echo 0x48000000 > /sys/devices/system/memory/probe
[   28.693675] init_memory_mapping: [mem 0x48000000-0x4fffffff]
 # echo online_movable > /sys/devices/system/memory/memory9/state
 # echo 0x50000000 > /sys/devices/system/memory/probe 
[   29.084090] init_memory_mapping: [mem 0x50000000-0x57ffffff]
 # echo 0x58000000 > /sys/devices/system/memory/probe 
[   29.151880] init_memory_mapping: [mem 0x58000000-0x5fffffff]
 # echo online_movable > /sys/devices/system/memory/memory11/state
 # echo online> /sys/devices/system/memory/memory8/state
 # echo online> /sys/devices/system/memory/memory10/state
 # echo offline> /sys/devices/system/memory/memory9/state
[   30.558819] Offlined Pages 32768
 # free
             total       used       free     shared    buffers     cached
Mem:        780588 18014398509432020     830552          0          0      51180
-/+ buffers/cache: 18014398509380840     881732
Swap:            0          0          0

This is because the above commands probe higher memory after online a
section with online_movable, which causes ZONE_HIGHMEM (or ZONE_NORMAL
for systems without ZONE_HIGHMEM) overlaps ZONE_MOVABLE.

After the second online_movable, the problem can be observed from
zoneinfo:

 # cat /proc/zoneinfo
...
Node 0, zone  Movable
  pages free     65491
        min      250
        low      312
        high     375
        scanned  0
        spanned  18446744073709518848
        present  65536
        managed  65536
...

This series of patches solve the problem by checking ZONE_MOVABLE when
choosing zone for new memory. If new memory is inside or higher than
ZONE_MOVABLE, makes it go there instead.


Wang Nan (5):
  memory-hotplug: x86_64: suitable memory should go to ZONE_MOVABLE
  memory-hotplug: x86_32: suitable memory should go to ZONE_MOVABLE
  memory-hotplug: ia64: suitable memory should go to ZONE_MOVABLE
  memory-hotplug: sh: suitable memory should go to ZONE_MOVABLE
  memory-hotplug: powerpc: suitable memory should go to ZONE_MOVABLE

 arch/ia64/mm/init.c   |  7 +++++++
 arch/powerpc/mm/mem.c |  6 ++++++
 arch/sh/mm/init.c     | 13 ++++++++-----
 arch/x86/mm/init_32.c |  6 ++++++
 arch/x86/mm/init_64.c | 10 ++++++++--
 5 files changed, 35 insertions(+), 7 deletions(-)

-- 
1.8.4

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