Re: FW: [LSF/MM/BPF TOPIC] BoF VM live migration over CXL memory

[Matthew Wilcox <willy@infradead.org>]

On Wed, Apr 12, 2023 at 08:10:33PM +0900, Kyungsan Kim wrote:
> Pinning and plubbability is mutual exclusive so it can not happen at the same time.
> What we argue is ZONE_EXMEM does not "confine movability". an allocation context can determine the movability attribute.
> Even one unmovable allocation will make the entire CXL DRAM unpluggable. 
> When you see ZONE_EXMEM just on movable/unmoable aspect, we think it is the same with ZONE_NORMAL,
> but ZONE_EXMEM works on an extended memory, as of now CXL DRAM.
> 
> Then why ZONE_EXMEM is, ZONE_EXMEM considers not only the pluggability aspect, but CXL identifier for user/kenelspace API, 
> the abstraction of multiple CXL DRAM channels, and zone unit algorithm for CXL HW characteristics.
> The last one is potential at the moment, though.
> 
> As mentioned in ZONE_EXMEM thread, we are preparing slides to explain experiences and proposals.
> It it not final version now[1].
> [1] https://github.com/OpenMPDK/SMDK/wiki/93.-%5BLSF-MM-BPF-TOPIC%5D-SMDK-inspired-MM-changes-for-CXL

The problem is that you're starting out with a solution.  Tell us what
your requirements are, at a really high level, then walk us through
why ZONE_EXMEM is the best way to satisfy those requirements.

Also, those slides are terrible.  Even at 200% zoom, the text is tiny.

There is no MAP_NORMAL argument to mmap(), there are no GFP flags to
sys_mmap() and calling mmap() does not typically cause alloc_page() to
be called.  I'm not sure that putting your thoughts onto slides is
making them any better organised.