On 03/13/2017 05:19 AM, Michal Hocko wrote:
On Fri 10-03-17 12:39:27, Yasuaki Ishimatsu wrote:
On 03/10/2017 08:58 AM, Michal Hocko wrote:
[...]
OK so I did with -m 2G,slots=4,maxmem=4G -numa node,mem=1G -numa node,mem=1G which generated
[...]
[ 0.000000] ACPI: SRAT: Node 0 PXM 0 [mem 0x00000000-0x0009ffff]
[ 0.000000] ACPI: SRAT: Node 0 PXM 0 [mem 0x00100000-0x3fffffff]
[ 0.000000] ACPI: SRAT: Node 1 PXM 1 [mem 0x40000000-0x7fffffff]
[ 0.000000] ACPI: SRAT: Node 0 PXM 0 [mem 0x100000000-0x27fffffff] hotplug
[ 0.000000] NUMA: Node 0 [mem 0x00000000-0x0009ffff] + [mem 0x00100000-0x3fffffff] -> [mem 0x00000000-0x3fffffff]
[ 0.000000] NODE_DATA(0) allocated [mem 0x3fffc000-0x3fffffff]
[ 0.000000] NODE_DATA(1) allocated [mem 0x7ffdc000-0x7ffdffff]
[ 0.000000] Zone ranges:
[ 0.000000] DMA [mem 0x0000000000001000-0x0000000000ffffff]
[ 0.000000] DMA32 [mem 0x0000000001000000-0x000000007ffdffff]
[ 0.000000] Normal empty
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000000001000-0x000000000009efff]
[ 0.000000] node 0: [mem 0x0000000000100000-0x000000003fffffff]
[ 0.000000] node 1: [mem 0x0000000040000000-0x000000007ffdffff]
so there is neither any normal zone nor movable one at the boot time.
Then I hotplugged 1G slot
(qemu) object_add memory-backend-ram,id=mem1,size=1G
(qemu) device_add pc-dimm,id=dimm1,memdev=mem1
unfortunatelly the memory didn't show up automatically and I got
[ 116.375781] acpi PNP0C80:00: Enumeration failure
so I had to probe it manually (prbably the BIOS my qemu uses doesn't
support auto probing - I haven't really dug further). Anyway the SRAT
table printed during the boot told that we should start at 0x100000000
# echo 0x100000000 > /sys/devices/system/memory/probe
# grep . /sys/devices/system/memory/memory32/valid_zones
Normal Movable
which looks reasonably right? Both Normal and Movable zones are allowed
# echo $((0x100000000+(128<<20))) > /sys/devices/system/memory/probe
# grep . /sys/devices/system/memory/memory3?/valid_zones
/sys/devices/system/memory/memory32/valid_zones:Normal
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
Huh, so our valid_zones have changed under our feet...
# echo $((0x100000000+2*(128<<20))) > /sys/devices/system/memory/probe
# grep . /sys/devices/system/memory/memory3?/valid_zones
/sys/devices/system/memory/memory32/valid_zones:Normal
/sys/devices/system/memory/memory33/valid_zones:Normal
/sys/devices/system/memory/memory34/valid_zones:Normal Movable
and again. So only the last memblock is considered movable. Let's try to
online them now.
# echo online_movable > /sys/devices/system/memory/memory34/state
# grep . /sys/devices/system/memory/memory3?/valid_zones
/sys/devices/system/memory/memory32/valid_zones:Normal
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
/sys/devices/system/memory/memory34/valid_zones:Movable Normal
I think there is no strong reason which kernel has the restriction.
By setting the restrictions, it seems to have made management of
these zone structs simple.
Could you be more specific please? How could this make management any
easier when udev is basically racing with the physical hotplug and the
result is basically undefined?
When changing zone from NORMAL(N) to MOVALBE(M), we must resize both zones,
zone->zone_start_pfn and zone->spanned_pages. Currently there is the
restriction.
So we just simply change:
zone(N)->spanned_pages -= nr_pages
zone(M)->zone_start_pfn -= nr_pages
But if every memory can change zone with no restriction, we must recalculate
these zones spanned_pages and zone_start_pfn follows:
memory section #
1 2 3 4 5 6 7
|N|M|N|N|N|M|M|
|
|N|N|N|N|N|M|M|
* change memory section #2 from MOVABLE to NORMAL.
then we must find next movable memory section (#6) and resize these zones.
I think when implementing movable memory, there is no requirement of this.
So kernel has the current restriction.
Thanks,
Yasuaki Ishimatsu
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