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

[Balbir Singh]

On Thu, Sep 7, 2017 at 5:21 PM, Benjamin Herrenschmidt
<benh at kernel.crashing.org> wrote:
> On Thu, 2017-09-07 at 15:17 +1000, Anton Blanchard wrote:
>> Hi,
>>
>> > There is a similar issue being worked on w.r.t pseries.
>> >
>> > https://lkml.kernel.org/r/1502357028-27465-1-git-send-email-bharata@linux.vnet.ibm.com
>> >
>> > The question is should we map these regions ? ie, we need to tell the
>> > kernel memory region that we would like to hot unplug later so that
>> > we avoid doing kernel allocations from that. If we do that, then we
>> > can possibly map them via 2M size ?
>>
>> But all of memory on PowerNV should be able to be hot unplugged, so

For this ideally we need movable mappings for the regions we intend
to hot-unplug - no? Otherwise, there is no guarantee that hot-unplug
will work

>> there are two options as I see it - either increase the memory block
>> size, or map everything with 2MB pages.
>
> Or be smarter and map with 1G when blocks of 1G are available and break
> down to 2M where necessary, it shouldn't be too hard.
>

strict_rwx patches added helpers to do this

Balbir Singh.