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

Wang Nan
2014-07-18T09:56:30Z

On 2014/7/18 17:16, Zhang Yanfei wrote:
> Hello,
>
> On 07/18/2014 03:55 PM, Wang Nan wrote:
>> 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.
>
> Yeah, this is rare in reality but can happen. Could you please also
> include the free result and zoneinfo after applying your patch?
>
> Thanks.
>

OK.

I paste the free result and zoneinfo at the end of this mail. This is a x86_64 result,
generated on qemu, after applying my patches.

I only tested x86_64 and x86_32 (and found a typo). Could any one can help me verify
other platforms?

Thanks.

>>
>> 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(-)
>>
>
>

After applying the above patches, here is the free result and zoneinfo (after offline memory9):

bash-4.2# free
total used free shared buffers cached
Mem: 780588 80860 699728 0 0 51180
-/+ buffers/cache: 29680 750908
Swap: 0 0 0

bash-4.2# cat /proc/zoneinfo

Node 0, zone DMA
pages free 3272
min 14
low 17
high 21
scanned 0
spanned 4095
present 3998
managed 3977
nr_free_pages 3272
...
start_pfn: 1
inactive_ratio: 1
Node 0, zone DMA32
pages free 73548
min 341
low 426
high 511
scanned 0
spanned 98304
present 98304
managed 92866
nr_free_pages 73548
...
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 65491
min 241
low 301
high 361
scanned 0
spanned 98304
present 65536
managed 65536
nr_free_pages 65491
...
start_pfn: 294912
inactive_ratio: 1