make scx_userland more robust #30
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If the scheduler fails to dispatch a task we immediately give up, exiting with an error like the following: Failed to dispatch task 251 in 1 EXIT: BPF scheduler unregistered This scenario can be simulated decreasing dramatically the value of MAX_ENQUEUED_TASKS. We can make the scheduler a little more robust simply by re-adding the task that cannot be dispatched to vruntime_head and stop dispatching additional tasks in the same batch. This can give enough room, under such "dispatch overload" condition, to catch up and resume the normal execution without crashing. Moreover, introduce nr_vruntime_failed to report failed dispatch events in the scheduler's statistics. Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
With commit 48bba8e ("scx_userland: survive to dispatch failures") scx_useland can better tolerate dispatch failures, so we can reduce a bit MAX_ENQUEUED_TASKS and align it with the size used in bpf_repeat(), when tasks are actually dispatched in the bpf counterpart. This allows reducing the memory footprint of the scheduler and makes it more consistent between enqueue and dispatch events. Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
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Allow to handle dispatch failure events without crashing, reduce MAX_ENQUEUED_TASKS to improve memory footprint and make enqueue/dispatch events more consistent.