Messages in this thread Patch in this message | | | Subject | [PATCH 1/3] sched/fair: Disable runtime_enabled on dying rq | From | Kirill Tkhai <> | Date | Tue, 17 Jun 2014 17:24:10 +0400 |
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We kill rq->rd on the CPU_DOWN_PREPARE stage:
cpuset_cpu_inactive -> cpuset_update_active_cpus -> partition_sched_domains -> -> cpu_attach_domain -> rq_attach_root -> set_rq_offline
This unthrottles all throttled cfs_rqs.
But the cpu is still able to call schedule() till
take_cpu_down->__cpu_disable()
is called from stop_machine.
This case the tasks from just unthrottled cfs_rqs are pickable in a standard scheduler way, and they are picked by dying cpu. The cfs_rqs becomes throttled again, and migrate_tasks() in migration_call skips their tasks (one more unthrottle in migrate_tasks()->CPU_DYING does not happen, because rq->rd is already NULL).
Patch sets runtime_enabled to zero. This guarantees, the runtime is not accounted, and the cfs_rqs won't exceed given cfs_rq->runtime_remaining = 1, and tasks will be pickable in migrate_tasks(). runtime_enabled is recalculated again when rq becomes online again.
Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> CC: Srikar Dronamraju <srikar@linux.vnet.ibm.com> CC: Mike Galbraith <umgwanakikbuti@gmail.com> CC: Peter Zijlstra <peterz@infradead.org> CC: Ingo Molnar <mingo@kernel.org> --- kernel/sched/fair.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index fea7d33..f120525 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3775,6 +3775,19 @@ static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) hrtimer_cancel(&cfs_b->slack_timer); } +static void __maybe_unused update_runtime_enabled(struct rq *rq) +{ + struct cfs_rq *cfs_rq; + + for_each_leaf_cfs_rq(rq, cfs_rq) { + struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth; + + raw_spin_lock(&cfs_b->lock); + cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF; + raw_spin_unlock(&cfs_b->lock); + } +} + static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq) { struct cfs_rq *cfs_rq; @@ -3790,6 +3803,12 @@ static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq) cfs_rq->runtime_remaining = 1; if (cfs_rq_throttled(cfs_rq)) unthrottle_cfs_rq(cfs_rq); + + /* + * Offline rq is schedulable till cpu is completely disabled + * in take_cpu_down(), so we prevent new cfs throttling here. + */ + cfs_rq->runtime_enabled = 0; } } @@ -3831,6 +3850,7 @@ static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) return NULL; } static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} +static inline void update_runtime_enabled(struct rq *rq) {} static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {} #endif /* CONFIG_CFS_BANDWIDTH */ @@ -7325,6 +7345,8 @@ void trigger_load_balance(struct rq *rq) static void rq_online_fair(struct rq *rq) { update_sysctl(); + + update_runtime_enabled(rq); } static void rq_offline_fair(struct rq *rq)
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