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This current patch series seems to > > > > drop the first distinction, allowing a partially idle preferred core to win even > > > > when another preferred core is fully idle. > > > > > > > > This would need to coexist with the steal governor's stronger use of > > > > cpu_preferred_mask, so I'm suggesting it as a potential direction to explore > > > > rather than a drop-in replacement. > > > > I think this makes a lot of sense. An approach to first fill preferred > > CPUs before spilling to the non-preferred cores until contention > > forces the evacuation of non-prefered CPUs. > > Well, when we see steal time, it usually means there is high contention and > we are using more vCPUs at this moment than possible. > So we mark them as non-preferred. Note that they are idle cpus. But non-preferred. > > That means preferred CPUs may have more than 1 task. If we spill over if there > is idle non-preferred CPUs, we will be back to square one. No? I agree that CPUs excluded by the steal governor should remain avoided even when all preferred CPUs are busy. I'm wondering if we should have two levels: cpu_preferred_mask acting as a hard affinity constraint and an entitlement-based soft affinity within that mask? The soft affinity would prefer high-entitlement CPUs: first fully idle cores, then idle SMT siblings. Once those CPUs are busy, tasks could spill onto lower-entitlement CPUs still inside cpu_preferred_mask, again preferring fully idle cores over idle SMT siblings. If all CPUs inside cpu_preferred_mask are busy, tasks would queue there. The soft affinity would never override the governor's restriction by spilling onto CPUs it excluded due to contention. Thanks, -Andrea