[PATCH v2 0/7] memory-hotplug: suitable memory should go to ZONE_MOVABLE

Wang Nan
2014-07-21T03:46:35Z

This series of patches fix a problem when adding memory in bad manner.
For example: for a x86_64 machine booted with "mem@0M" 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.

After applying this series of patches, following are free and zoneinfo
result (after offlining memory9):

bash-4.2# free
total used free shared buffers cached
Mem: 780956 80112 700844 0 0 51180
-/+ buffers/cache: 28932 752024
Swap: 0 0 0

bash-4.2# cat /proc/zoneinfo

Node 0, zone DMA
pages free 3389
min 14
low 17
high 21
scanned 0
spanned 4095
present 3998
managed 3977
nr_free_pages 3389
...
start_pfn: 1
inactive_ratio: 1
Node 0, zone DMA32
pages free 73724
min 341
low 426
high 511
scanned 0
spanned 98304
present 98304
managed 92958
nr_free_pages 73724
...
start_pfn: 4096
inactive_ratio: 1
Node 0, zone Normal
pages free 32630
min 120
low 150
high 180
scanned 0
spanned 32768
present 32768
managed 32768
nr_free_pages 32630
...
start_pfn: 262144
inactive_ratio: 1
Node 0, zone Movable
pages free 65476
min 241
low 301
high 361
scanned 0
spanned 98304
present 65536
managed 65536
nr_free_pages 65476
...
start_pfn: 294912
inactive_ratio: 1

v1 -> v2:
- introduce zone_for_memory() to arch independent code to make arch
dependent code simpler, following Dave Hansen's comments.
- Paste free and zoneinfo result in patch 0 as a response to
Zhang Yanfei.
- Fix a problem in tile to add memory into ZONE_HIGHMEM by default.

Wang Nan (7):
memory-hotplug: add zone_for_memory() for selecting zone for new
memory
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: ppc: suitable memory should go to ZONE_MOVABLE
memory-hotplug: sh: suitable memory should go to ZONE_MOVABLE
memory-hotplug: tile: suitable memory should go to ZONE_MOVABLE

arch/ia64/mm/init.c | 3 ++-
arch/powerpc/mm/mem.c | 3 ++-
arch/sh/mm/init.c | 5 +++--
arch/tile/mm/init.c | 3 ++-
arch/x86/mm/init_32.c | 3 ++-
arch/x86/mm/init_64.c | 3 ++-
include/linux/memory_hotplug.h | 1 +
mm/memory_hotplug.c | 28 ++++++++++++++++++++++++++++
8 files changed, 42 insertions(+), 7 deletions(-)

--
1.8.4