Re: [RFC PATCH 0/8] sched: Extend cache-aware scheduling into topology-aware scheduling

[Peter Zijlstra]

On Thu, Jun 25, 2026 at 11:07:51AM +0800, Jianyong Wu wrote:
> The current cache-aware scheduling implementation adopts an
> LLC-centric task aggregation model. While effective for workloads
> that fit within a single LLC domain, this design is fundamentally
> limited by a fixed aggregation scope that cannot scale across
> scheduling domains.
> 
> This leads to a single structural limitation: the lack of
> topology-scalable task aggregation. When workload size exceeds
> the capacity of an LLC domain, the scheduler cannot extend
> aggregation to higher-level domains, and locality cannot be
> preserved effectively. At the same time, higher-level topology
> information such as NUMA domains cannot be consistently utilized
> for placement decisions.
> 
> This patch set addresses this limitation by extending
> cache-aware scheduling into topology-aware task aggregation.
> The aggregation scope becomes hierarchical and can dynamically
> expand or contract across scheduling domains based on workload
> demand.
> 
> Task aggregation starts at MC or LLC domains under light load,
> and expands to NUMA and higher-level domains as load increases,
> and contracts when load decreases.

Urgh,... that only really works if the topology has a low branching
factor.

I would much rather see things move towards a mask of cache domains,
rather than any single one, where the number of bits in the mask is
minimal vs the concurrency.

This has already been mentioned a number of times, which seems to
suggest you've not actually been reading along very well :-(