On 8/1/23 2:28 PM, Michal Hocko wrote:

On Tue 01-08-23 10:11:16, Aneesh Kumar K.V wrote:

quoted

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