Re: [PATCH v2 1/3] sched/numa: make free-space tiering promotion bypass configurable

[Bharata B Rao]

On 28-Oct-26 9:42 AM, Li Zhe wrote:
> Memory tiering normally promotes any recently accessed slow-tier page if
> the target fast-tier node has enough free space. This preserves the
> existing policy of filling available fast memory before relying on
> hotness and rate-limit control.
> 
> That is not always the desired policy. Some deployments may intentionally
> keep part of a workload's memory on CXL-attached memory, for example to
> preserve a desired DRAM/CXL capacity split or bandwidth distribution. With
> the free-space bypass, short cold accesses and bursts of hot accesses can
> refill the fast tier and pull the workload away from that distribution
> whenever DRAM has free space.

Currently promotion happens on 1st access. Won't it be more natural to tweak
this frequency of access and also the time between successive accesses to
prevent promotion due to short cold accesses and bursts of hot accesses
rather than free space bypass configuration?

Regards,
Bharata.