Re: collision between ZONE_MOVABLE and memblock allocations

[Ross Zwisler]

On Wed, Jul 19, 2023 at 08:44:34AM +0300, Mike Rapoport wrote:
> 3. Switch memblock to use bottom up allocations. Historically memblock
> allocated memory from the top to avoid corrupting the kernel image and to
> avoid exhausting precious ZONE_DMA. I believe we can use bottom-up
> allocations with lower limit of memblock allocations set to 16M.
> 
> With the hack below no memblock allocations will end up in ZONE_MOVABLE:

Yep, I've confirmed that for my use cases at least this does the trick, thank
you!  I had thought about moving the memblock allocations, but had no idea it
was (basically) already supported and thought it'd be much riskier than just
adjusting where ZONE_MOVABLE lived.

Is there a reason for this to not be a real option for users, maybe per a
kernel config knob or something?  I'm happy to explore other options in this
thread, but this is doing the trick so far.