Re: [PATCH v2 2/5] mm,memory_hotplug: Introduce MHP_VMEMMAP_FLAGS

From: Oscar Salvador
Date: Thu Jul 25 2019 - 14:05:12 EST

On Thu, Jul 25, 2019 at 12:04:08PM +0200, David Hildenbrand wrote:
> As I said somewhere already (as far as I recall), one mode would be
> sufficient. If you want per memblock, add the memory in memblock
> granularity.
> So having a MHP_MEMMAP_ON_MEMORY that allocates it in one chunk would be
> sufficient for the current use cases (DIMMs, Hyper-V).
> MHP_MEMMAP_ON_MEMORY: Allocate the memmap for the added memory in one
> chunk from the beginning of the added memory. This piece of memory will
> be accessed and used even before the memory is onlined.

This is what I had in my early versions of the patchset, but I do remember
that Michal suggested to let the caller specify if it wants the memmaps
to be allocated per memblock, or per whole-range.

I still think it makes somse sense, you can just pass a large chunk
(spanning multiple memory-blocks) at once and yet specify to allocate
it per memory-blocks.

Of course, I also agree that having only one mode would ease things
(not that much as v3 does not suppose that difference wrt. range vs

Oscar Salvador