Messages in this thread | | | Date | Mon, 30 Mar 2015 07:02:11 +0800 | From | Wanpeng Li <> | Subject | Re: [PATCH v14] sched/deadline: support dl task migration during cpu hotplug |
| |
Ping Ingo, ;) On Fri, Mar 27, 2015 at 07:08:35AM +0800, Wanpeng Li wrote: >I observe that dl task can't be migrated to other cpus during cpu hotplug, >in addition, task may/may not be running again if cpu is added back. The >root cause which I found is that dl task will be throtted and removed from >dl rq after comsuming all budget, which leads to stop task can't pick it up >from dl rq and migrate to other cpus during hotplug. > >The method to reproduce: >schedtool -E -t 50000:100000 -e ./test >Actually test is just a simple for loop. Then observe which cpu the test >task is on. >echo 0 > /sys/devices/system/cpu/cpuN/online > >This patch adds the dl task migration during cpu hotplug by finding a most >suitable later deadline rq after dl timer fire if current rq is offline, >if fail to find a suitable later deadline rq then fallback to any eligible >online cpu in order that the deadline task will come back to us, and the >push/pull mechanism should then move it around properly. > >Suggested-and-acked-by: Juri Lelli <juri.lelli@arm.com> >Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com> >--- >v13 -> 14: > * have better naming > * simply the BUG_ON part >v12 -> 13: > * move hotplug stuff to CONFIG_SMP in order to fix the error reported by kbuild test robot >v11 -> v12: > * s/WARN_ON/BUG_ON >v10 -> v11: > * fix codes comments > * tsk_cpus_allowed(p) shouldn't be on separate lines > * introduce a helper function to fold dl task migration during cpu hotplug support >v9 -> v10: > * fix the "WARNING: line over 80 characters" > * handle no admission control >v8 -> v9: > * align tsk_cpus_allowed(p) to cpu_active_mask > * add WARN_ON(1) > * don't resched_curr if later_rq come from the cpumask_any_and() >v7 -> v8: > * remove rd->span related modification since Pang's commit 16b269436b72 > (sched/deadline: Modify cpudl::free_cpus to reflect rd->online) merged > upstream, which Juri pointed out can handle the exclusive cpusets. > * rebase >v6 -> v7: > * rebase >v5 -> v6: > * add double_lock_balance in the fallback path >v4 -> v5: > * remove raw_spin_unlock(&rq->lock) > * cleanup codes, spotted by Peterz > * cleanup patch description >v3 -> v4: > * use tsk_cpus_allowed wrapper > * fix compile error >v2 -> v3: > * don't get_task_struct > * if cannot preempt any rq, fallback to pick any online cpus > * use cpu_active_mask as original later_mask if cpu is offline >v1 -> v2: > * push the task to another cpu in dl_task_timer() if rq is offline. > > kernel/sched/deadline.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 57 insertions(+) > >diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c >index 24c18dc..12eb314 100644 >--- a/kernel/sched/deadline.c >+++ b/kernel/sched/deadline.c >@@ -218,6 +218,52 @@ static inline void set_post_schedule(struct rq *rq) > rq->post_schedule = has_pushable_dl_tasks(rq); > } > >+static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq); >+ >+static void dl_task_offline_migration(struct rq *rq, struct task_struct *p) >+{ >+ struct rq *later_rq = NULL; >+ bool fallback = false; >+ >+ later_rq = find_lock_later_rq(p, rq); >+ >+ if (!later_rq) { >+ int cpu; >+ >+ /* >+ * If we cannot preempt any rq, fall back to pick any >+ * online cpu. >+ */ >+ fallback = true; >+ cpu = cpumask_any_and(cpu_active_mask, tsk_cpus_allowed(p)); >+ if (cpu >= nr_cpu_ids) { >+ /* >+ * Fail to find any suitable cpu. >+ * The task will never come back! >+ */ >+ BUG_ON(dl_bandwidth_enabled()); >+ >+ /* >+ * If admission control is disabled we >+ * try a little harder to let the task >+ * run. >+ */ >+ cpu = cpumask_any(cpu_active_mask); >+ } >+ later_rq = cpu_rq(cpu); >+ double_lock_balance(rq, later_rq); >+ } >+ >+ deactivate_task(rq, p, 0); >+ set_task_cpu(p, later_rq->cpu); >+ activate_task(later_rq, p, ENQUEUE_REPLENISH); >+ >+ if (!fallback) >+ resched_curr(later_rq); >+ >+ double_unlock_balance(rq, later_rq); >+} >+ > #else > > static inline >@@ -536,6 +582,17 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer) > sched_clock_tick(); > update_rq_clock(rq); > >+#ifdef CONFIG_SMP >+ /* >+ * If we find that the rq the task was on is no longer >+ * available, we need to select a new rq. >+ */ >+ if (unlikely(!rq->online)) { >+ dl_task_offline_migration(rq, p); >+ goto unlock; >+ } >+#endif >+ > /* > * If the throttle happened during sched-out; like: > * >-- >1.9.1
| |