[PATCH v7 7/7] mm/memory_hotplug: Enable runtime update of memmap_on_memory parameter

[Aneesh Kumar K V]

On 8/1/23 2:28 PM, Michal Hocko wrote:
> On Tue 01-08-23 10:11:16, Aneesh Kumar K.V wrote:
>> Allow updating memmap_on_memory mode after the kernel boot. Memory
>> hotplug done after the mode update will use the new mmemap_on_memory
>> value.
> 
> Well, this is a user space kABI extension and as such you should spend
> more words about the usecase. Why we could live with this static and now
> need dynamic?
> 

This enables easy testing of memmap_on_memory feature without a kernel reboot.
I also expect people wanting to use that when they find dax kmem memory online
failing because of struct page allocation failures[1]. User could reboot back with
memmap_on_memory=y kernel parameter. But being able to enable it via sysfs makes
the feature much more useful.

-aneesh