scx_flatcg: Fix fallout from direct dispatch API update #82
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To improve visibility into failure mode. While at it, improve output formatting. Signed-off-by: Tejun Heo <tj@kernel.org>
552b75a ("scx: Build fix after kernel update") updated scx_flatcg along with other schedulers to use the new direct dispatching from ops.select_cpu() mechanism. However, this was buggy for flatcg. flatcg uses direct dispatch for two purposes - as an optimization when there are idle cpus and to avoid dealing with custom CPU affinities in the dispatch logic. While the former can be moved to ops.select_cpu(), the latter can't as it should also apply to tasks which get enqueued without preceding ops.select_cpu(), e.g., when the task gets requeued after an attribute change or runs out of time slice. The API update incorrectly moved both to ops.select_cpu() leading to futile retries of try_pick_next_cgroup() and scheduling misbheaviors. Fix it by separating out the two cases and only keeping the idle optimization case in ops.select_cpu(). Signed-off-by: Tejun Heo <tj@kernel.org>
arighi
approved these changes
Jan 10, 2024
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flatcg was busy spinning on
try_pick_next_cgroup()due to tasks w/ custom affinities being put on cgroup dsq's. Fix it and improve misbehavior visibility.