Hi Xishi,

Thanks for the reply - please see comments below.

On 16-12-01 05:49 PM, Xishi Qiu wrote:
On 2016/12/2 8:19, Scott Branden wrote:

This patchset is sent for comment to add memory hotplug support for ARM64
based platforms.  It follows hotplug code added for other architectures
in the linux kernel.

I tried testing the memory hotplug feature following documentation from
Documentation/memory-hotplug.txt.  I don't think it is working as expected
- see below:

To add memory to the system I did the following:
echo 0x400000000 > /sys/devices/system/memory/probe

The memory is displayed as system ram:
cat /proc/iomem:
74000000-77ffffff : System RAM
  74080000-748dffff : Kernel code
  74950000-749d2fff : Kernel data
400000000-43fffffff : System RAM

But does not seem to be added to the kernel memory.
/proc/meminfo did not change.

What else needs to be done so the memory is added to the kernel memory
pool for normal allocation?


Hi Scott,

Do you mean it still don't support hod-add after apply this patchset?

After applying the patch it appears to partially support hot-add. Please let me know if you think it is working as expected?

The memory probe functions in that the memory is registered with the system and shows up in /proc/iomem. But, the memory is not available in /proc/meminfo. Do you think something else needs to be adjusted for ARM64 to hotadd the memory

I just found another clue:
under /sys/devices/system/memory I only see one memory entry (before or after I try to hotadd additional memory).

/sys/devices/system/memory # ls
auto_online_blocks  memory0            uevent
block_size_bytes    probe

In arch/arm64/include/asm/sparsemem.h if I change SECTION_SIZE_BITS from 30 to 28 and recompile I get the following:
/sys/devices/system/memory # ls
auto_online_blocks  memory7            uevent
block_size_bytes    probe


In arch/arm64/include/asm/sparsemem.h if I change SECTION_SIZE_BITS from 30 to 27 and recompile I get the following:
/sys/devices/system/memory # ls
auto_online_blocks  memory14            uevent
block_size_bytes    probe

If looks to me like something is not working properly in the ARM64 implementation. I should expect to see multiple memoryX entries under /sys/devices/system/memory?




Thanks,
Xishi Qiu

Scott Branden (2):
  arm64: memory-hotplug: Add MEMORY_HOTPLUG, MEMORY_HOTREMOVE,
    MEMORY_PROBE
  arm64: defconfig: enable MEMORY_HOTPLUG config options

 arch/arm64/Kconfig           | 10 ++++++++++
 arch/arm64/configs/defconfig |  3 +++
 arch/arm64/mm/init.c         | 42 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+)




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