scx_bpfland: Rethink per-CPU tasks prioritization #2987
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Now that we always pick the task with the earliest deadline between the per-node DSQ and per-CPU DSQ, see commit 9cb2779 ("scx_bpfland: Avoid starvation in per-node DSQs"), we can always dispatch per-CPU tasks to the corresponding per-CPU DSQ and reduce the locking pressure on the per-node DSQs, without regressing system responsiveness. Moreover, change per-CPU tasks prioritization (option --local-pcpu / -p) to always dispatch per-CPU tasks to the local DSQ (SCX_DSQ_LOCAL). With this option enabled, strictly affinitized tasks may still starve non-affinitized ones (as before), but they also receive a higher priority, which can be beneficial for certain workloads. Signed-off-by: Andrea Righi <[email protected]>
sirlucjan
approved these changes
Oct 30, 2025
hodgesds
approved these changes
Oct 31, 2025
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Now that we always pick the task with the earliest deadline between the per-node DSQ and per-CPU DSQ, see commit 9cb2779 ("scx_bpfland: Avoid starvation in per-node DSQs"), we can always dispatch per-CPU tasks to the corresponding per-CPU DSQ and reduce the locking pressure on the per-node DSQs, without regressing system responsiveness.
Moreover, change per-CPU tasks prioritization (option --local-pcpu / -p) to always dispatch per-CPU tasks to the local DSQ (SCX_DSQ_LOCAL). With this option enabled, strictly affinitized tasks may still starve non-affinitized ones (as before), but they also receive a higher priority, which can be beneficial for certain workloads.