Returning prev_cpu after picking an idle CPU will cause the idle CPU
stall because the idle core was already punched out from the idle mask
by the scx core so it is no longer idle from the scx core's point of
view.
This fix conducts the idle core selection at the last step so it never
return prev_cpu after picking the idle core.
Signed-off-by: Changwoo Min <changwoo@igalia.com>
get_task_ctx() and try_get_task_ctx() were added for common error
handling for task lookup failure. Since idle "swapper" task is not under
sched_ext, try_get_task_ctx() is added for the case such that idle task
can be searched.
Signed-off-by: Changwoo Min <changwoo@igalia.com>
We don't need to test SCX_WAKE_SYNC because SCX_WAKE_SYNC should only be
set when SCX_WAKE_TTWU is set.
Signed-off-by: Changwoo Min <changwoo@igalia.com>
scx_lavd is a BPF scheduler that implements an LAVD (Latency-criticality
Aware Virtual Deadline) scheduling algorithm. While LAVD is new and
still evolving, its core ideas are 1) measuring how much a task is
latency critical and 2) leveraging the task's latency-criticality
information in making various scheduling decisions (e.g., task's
deadline, time slice, etc.). As the name implies, LAVD is based on the
foundation of deadline scheduling. This scheduler consists of the BPF
part and the rust part. The BPF part makes all the scheduling decisions;
the rust part loads the BPF code and conducts other chores (e.g.,
printing sampled scheduling decisions).
