Re: [PATCH v2] sched/fair: Prefer cache locality for EAS wakeup

[Christian Loehle]

On 10/31/25 18:11, Christian Loehle wrote:
> On 10/31/25 16:59, Shubhang Kaushik OS wrote:
>> Yes, I agree that EAS approach is not suitable in this case as they require a heterogenous CPU topology.
>> The issue is that the existing checks are for a completely idle CPU, whereas `cpu_overutilized` implies
>> the CPU is busy but not yet overloaded. I ventured into EAS as this `cpu_overutilized` relies on
>> `sched_energy_enabled()` being active. The point I wanted to convey is that - we still need a `cpu_busy?`
>> check to make use of the cache locality - for SMP systems. Would appreciate some pointers on the same lines..
> 
> So the main issue is that with existing code if a CPU is "overloaded" isn't all that well defined.
> For EAS we know if !rd->overloaded => all CPUs are !cpu_overutilized(). We could just pick any where

rd->overutilized is what I meant of course...
Hopefully the point is still clear, with EAS (and CAS given some limitations) we can answer the "is this
CPU _busy_?" question by just looking at that CPU.