Re: [PATCH v2 2/4] mm: allow shared folios to be promoted to a fast tier

[David Hildenbrand (Arm)]

On 9/18/26 15:54, Gregory Price wrote:
> On Fri, Sep 18, 2026 at 02:53:40PM +0200, David Hildenbrand (Arm) wrote:
>> On 9/11/26 02:18, Gregory Price wrote:
>>> From: "Gregory Price (Meta)" <gourry@xxxxxxxxxx>
>>>
>>> NUMA balancing rejects shared copy-on-write folios and executable
>>> file folios mapped by multiple processes to avoid placement bouncing.
>>> These checks also block promotion from slow memory.
>>
>> Right. How to we know the direction of promotion vs. demotion, though?
>>
> 
> numa balancing never demotes.  It either:
> 
> 1) moves between sockets (nodes w/ N_CPU) (NORMAL)
>  or
> 2) moves from !top_tier to top_tier (TIERING)
> 
> Demotion is only enacted in reclaim / vmscan, and has no coupling with
> numa balancing.
> 

Valuable to briefly mention that here, and have some helper functions that make
this obvious (and maybe document it as well ;) ) :)


-- 
Cheers,

David