scx_lavd: support yield-based preemption #274
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If there is a higher priority task when running ops.tick(), ops.select_cpu(), and ops.enqueue() callbacks, the current running tasks yields its CPU by shrinking time slice to zero and a higher priority task can run on the current CPU. As low-cost, fine-grained preemption becomes available, default parameters are adjusted as follows: - Raise the bar for remote CPU preemption to avoid IPIs. - Increase the maximum time slice. - Gradually enforce the fair use of CPU time (i.e., ineligible duration) Lastly, using CAS, we ensure that a remote CPU is preempted by only one CPU. This removes unnecessary remote preemptions (and IPIs). Signed-off-by: Changwoo Min <[email protected]>
htejun
approved these changes
May 9, 2024
Signed-off-by: Changwoo Min <[email protected]>
This was referenced May 10, 2024
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If there is a higher priority task when running ops.tick(), ops.select_cpu(), and ops.enqueue() callbacks, the current running tasks yields its CPU by shrinking time slice to zero and a higher priority task can run on the current CPU.
As low-cost, fine-grained preemption becomes available, default parameters are adjusted as follows:
Lastly, using CAS, we ensure that a remote CPU is preempted by only one CPU. This removes unnecessary remote preemptions (and IPIs).