linux/kernel/sched/debug.c, branch v6.14

Merge tag 'sched-urgent-2025-02-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2025-02-08T19:16:22Z

Pull scheduler fixes from Ingo Molnar: "Fix a cfs_rq->h_nr_runnable accounting bug that trips up a defensive SCHED_WARN_ON() on certain workloads. The bug is believed to be (accidentally) self-correcting, hence no behavioral side effects are expected. Also print se.slice in debug output, since this value can now be set via the syscall ABI and can be useful to track" * tag 'sched-urgent-2025-02-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/debug: Provide slice length for fair tasks sched/fair: Fix inaccurate h_nr_runnable accounting with delayed dequeue

sched/debug: Provide slice length for fair tasks

2025-01-31T09:45:33Z

Since commit: 857b158dc5e8 ("sched/eevdf: Use sched_attr::sched_runtime to set request/slice suggestion") ... we have the userspace per-task tunable slice length, which is a key parameter that is otherwise difficult to obtain, so provide it in /proc/$PID/sched. [ mingo: Clarified the changelog. ] Signed-off-by: Christian Loehle Signed-off-by: Ingo Molnar Cc: Peter Zijlstra Link: https://lore.kernel.org/r/453349b1-1637-42f5-a7b2-2385392b5956@arm.com

sched/debug: Change need_resched warnings to pr_err

2025-01-13T13:10:23Z

need_resched warnings, if enabled, are treated as WARNINGs. If kernel.panic_on_warn is enabled, then this causes a kernel panic. It's highly unlikely that a panic is desired for these warnings, only a stack trace is normally required to debug and resolve. Thus, switch need_resched warnings to simply be a printk with an associated stack trace so they are no longer in scope for panic_on_warn. Signed-off-by: David Rientjes Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Madadi Vineeth Reddy Acked-by: Josh Don Link: https://lkml.kernel.org/r/e8d52023-5291-26bd-5299-8bb9eb604929@google.com

sched/fair: Rename cfs_rq.nr_running into nr_queued

2024-12-09T10:48:12Z

Rename cfs_rq.nr_running into cfs_rq.nr_queued which better reflects the reality as the value includes both the ready to run tasks and the delayed dequeue tasks. Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dietmar Eggemann Link: https://lore.kernel.org/r/20241202174606.4074512-10-vincent.guittot@linaro.org

sched/fair: Remove unused cfs_rq.idle_nr_running

2024-12-09T10:48:12Z

cfs_rq.idle_nr_running field is not used anywhere so we can remove the useless associated computation. Last user went in commit 5e963f2bd465 ("sched/fair: Commit to EEVDF"). Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dietmar Eggemann Link: https://lore.kernel.org/r/20241202174606.4074512-9-vincent.guittot@linaro.org

sched/fair: Rename cfs_rq.idle_h_nr_running into h_nr_idle

2024-12-09T10:48:12Z

Use same naming convention as others starting with h_nr_* and rename idle_h_nr_running into h_nr_idle. The "running" is not correct anymore as it includes delayed dequeue tasks as well. Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dietmar Eggemann Link: https://lore.kernel.org/r/20241202174606.4074512-8-vincent.guittot@linaro.org

sched/fair: Removed unsued cfs_rq.h_nr_delayed

2024-12-09T10:48:11Z

h_nr_delayed is not used anymore. We now have: - h_nr_runnable which tracks tasks ready to run - h_nr_queued which tracks enqueued tasks either ready to run or delayed dequeue Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dietmar Eggemann Link: https://lore.kernel.org/r/20241202174606.4074512-7-vincent.guittot@linaro.org

sched/fair: Add new cfs_rq.h_nr_runnable

2024-12-09T10:48:11Z

With delayed dequeued feature, a sleeping sched_entity remains queued in the rq until its lag has elapsed. As a result, it stays also visible in the statistics that are used to balance the system and in particular the field cfs.h_nr_queued when the sched_entity is associated to a task. Create a new h_nr_runnable that tracks only queued and runnable tasks. Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dietmar Eggemann Link: https://lore.kernel.org/r/20241202174606.4074512-5-vincent.guittot@linaro.org

sched/fair: Rename h_nr_running into h_nr_queued

2024-12-09T10:48:11Z

With delayed dequeued feature, a sleeping sched_entity remains queued in the rq until its lag has elapsed but can't run. Rename h_nr_running into h_nr_queued to reflect this new behavior. Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dietmar Eggemann Link: https://lore.kernel.org/r/20241202174606.4074512-4-vincent.guittot@linaro.org

sched/eevdf: More PELT vs DELAYED_DEQUEUE

2024-12-09T10:48:09Z

Vincent and Dietmar noted that while commit fc1892becd56 ("sched/eevdf: Fixup PELT vs DELAYED_DEQUEUE") fixes the entity runnable stats, it does not adjust the cfs_rq runnable stats, which are based off of h_nr_running. Track h_nr_delayed such that we can discount those and adjust the signal. Fixes: fc1892becd56 ("sched/eevdf: Fixup PELT vs DELAYED_DEQUEUE") Closes: https://lore.kernel.org/lkml/a9a45193-d0c6-4ba2-a822-464ad30b550e@arm.com/ Closes: https://lore.kernel.org/lkml/CAKfTPtCNUvWE_GX5LyvTF-WdxUT=ZgvZZv-4t=eWntg5uOFqiQ@mail.gmail.com/ [ Fixes checkpatch warnings and rebased ] Signed-off-by: Peter Zijlstra (Intel) Reported-by: Dietmar Eggemann Reported-by: Vincent Guittot Signed-off-by: "Peter Zijlstra (Intel)" Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dietmar Eggemann Tested-by: K Prateek Nayak Link: https://lore.kernel.org/r/20241202174606.4074512-3-vincent.guittot@linaro.org