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

Wang Nan
2014-07-18T08:10:20Z

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