Re: [PATCH] powerpc/pseries: Increase memory block size to 1GB on radix

[Balbir Singh <bsingharora@gmail.com>]

On Fri, Dec 22, 2017 at 4:06 PM, Michael Ellerman <mpe@ellerman.id.au> wrote:
> Michael Ellerman <mpe@ellerman.id.au> writes:
>
>> When we're using the Radix MMU we map the kernel linear mapping with
>> 1G pages. That means we must do memory hot remove in blocks of at
>> least that size. Otherwise the linear mapping can end up not mapping
>> all of memory because we've removed part of a 1G region but unmapped
>> the entire 1G region from the linear mapping.
>>
>> Currently on pseries we consult the device tree to find out the the
>> "LMB" (Logical Memory Block) size. This is the unit of memory hotplug
>> communicated to us by the hypervisor, but it does not take into
>> account anything the kernel has done itself, such as use 1G pages for
>> the linear mapping.
>
> This patch failed to survive contact with reality. ie. it doesn't work.
>
> NAK.


I have patches to split the size of a region, I guess the right thing to do is
to split the size of mapping during hotplug. I can look at doing that once I
am back. What broke for you during testing?

Balbir Singh.