sched/fair: Unify switched_{from,to}_fair() and task_move_group_fair()
By observing that switched_from_fair() detaches from a runqueue, and switched_to_fair() attaches to a runqueue, we can see that task_move_group_fair() is one followed by the other with flipping the runqueue in between. Therefore extract all the common bits and implement all three functions in terms of them. This should fix a few corner cases wrt. vruntime normalization; where, when we take a task off of a runqueue we convert to an approximation of lag by subtracting min_vruntime, and when placing a task on the a runqueue to the reverse. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Byungchul Park <byungchul.park@lge.com> [peterz: Changelog] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: yuyang.du@intel.com Link: http://lkml.kernel.org/r/1440069720-27038-6-git-send-email-byungchul.park@lge.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -7924,21 +7924,39 @@ prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
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check_preempt_curr(rq, p, 0);
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}
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static void switched_from_fair(struct rq *rq, struct task_struct *p)
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static inline bool vruntime_normalized(struct task_struct *p)
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{
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struct sched_entity *se = &p->se;
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/*
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* In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
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* the dequeue_entity(.flags=0) will already have normalized the
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* vruntime.
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*/
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if (p->on_rq)
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return true;
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/*
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* When !on_rq, vruntime of the task has usually NOT been normalized.
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* But there are some cases where it has already been normalized:
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*
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* - A forked child which is waiting for being woken up by
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* wake_up_new_task().
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* - A task which has been woken up by try_to_wake_up() and
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* waiting for actually being woken up by sched_ttwu_pending().
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*/
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if (!se->sum_exec_runtime || p->state == TASK_WAKING)
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return true;
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return false;
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}
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static void detach_task_cfs_rq(struct task_struct *p)
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{
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struct sched_entity *se = &p->se;
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struct cfs_rq *cfs_rq = cfs_rq_of(se);
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/*
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* Ensure the task's vruntime is normalized, so that when it's
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* switched back to the fair class the enqueue_entity(.flags=0) will
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* do the right thing.
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*
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* If it's queued, then the dequeue_entity(.flags=0) will already
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* have normalized the vruntime, if it's !queued, then only when
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* the task is sleeping will it still have non-normalized vruntime.
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*/
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if (!task_on_rq_queued(p) && p->state != TASK_RUNNING) {
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if (!vruntime_normalized(p)) {
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/*
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* Fix up our vruntime so that the current sleep doesn't
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* cause 'unlimited' sleep bonus.
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@ -7951,9 +7969,10 @@ static void switched_from_fair(struct rq *rq, struct task_struct *p)
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detach_entity_load_avg(cfs_rq, se);
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}
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static void switched_to_fair(struct rq *rq, struct task_struct *p)
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static void attach_task_cfs_rq(struct task_struct *p)
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{
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struct sched_entity *se = &p->se;
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struct cfs_rq *cfs_rq = cfs_rq_of(se);
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#ifdef CONFIG_FAIR_GROUP_SCHED
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/*
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@ -7964,24 +7983,22 @@ static void switched_to_fair(struct rq *rq, struct task_struct *p)
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#endif
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/* Synchronize task with its cfs_rq */
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attach_entity_load_avg(cfs_rq_of(&p->se), &p->se);
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attach_entity_load_avg(cfs_rq, se);
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if (!task_on_rq_queued(p)) {
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/*
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* Ensure the task has a non-normalized vruntime when it is switched
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* back to the fair class with !queued, so that enqueue_entity() at
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* wake-up time will do the right thing.
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*
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* If it's queued, then the enqueue_entity(.flags=0) makes the task
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* has non-normalized vruntime, if it's !queued, then it still has
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* normalized vruntime.
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*/
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if (p->state != TASK_RUNNING)
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se->vruntime += cfs_rq_of(se)->min_vruntime;
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return;
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if (!vruntime_normalized(p))
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se->vruntime += cfs_rq->min_vruntime;
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}
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static void switched_from_fair(struct rq *rq, struct task_struct *p)
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{
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detach_task_cfs_rq(p);
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}
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static void switched_to_fair(struct rq *rq, struct task_struct *p)
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{
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attach_task_cfs_rq(p);
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if (task_on_rq_queued(p)) {
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/*
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* We were most likely switched from sched_rt, so
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* kick off the schedule if running, otherwise just see
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@ -7992,6 +8009,7 @@ static void switched_to_fair(struct rq *rq, struct task_struct *p)
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else
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check_preempt_curr(rq, p, 0);
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}
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}
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/* Account for a task changing its policy or group.
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*
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@ -8027,57 +8045,14 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
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#ifdef CONFIG_FAIR_GROUP_SCHED
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static void task_move_group_fair(struct task_struct *p, int queued)
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{
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struct sched_entity *se = &p->se;
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struct cfs_rq *cfs_rq;
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/*
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* If the task was not on the rq at the time of this cgroup movement
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* it must have been asleep, sleeping tasks keep their ->vruntime
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* absolute on their old rq until wakeup (needed for the fair sleeper
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* bonus in place_entity()).
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*
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* If it was on the rq, we've just 'preempted' it, which does convert
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* ->vruntime to a relative base.
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*
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* Make sure both cases convert their relative position when migrating
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* to another cgroup's rq. This does somewhat interfere with the
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* fair sleeper stuff for the first placement, but who cares.
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*/
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/*
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* When !queued, vruntime of the task has usually NOT been normalized.
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* But there are some cases where it has already been normalized:
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*
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* - Moving a forked child which is waiting for being woken up by
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* wake_up_new_task().
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* - Moving a task which has been woken up by try_to_wake_up() and
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* waiting for actually being woken up by sched_ttwu_pending().
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*
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* To prevent boost or penalty in the new cfs_rq caused by delta
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* min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
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*/
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if (!queued && (!se->sum_exec_runtime || p->state == TASK_WAKING))
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queued = 1;
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cfs_rq = cfs_rq_of(se);
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if (!queued)
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se->vruntime -= cfs_rq->min_vruntime;
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/* Synchronize task with its prev cfs_rq */
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detach_entity_load_avg(cfs_rq, se);
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detach_task_cfs_rq(p);
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set_task_rq(p, task_cpu(p));
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#ifdef CONFIG_SMP
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/* Tell se's cfs_rq has been changed -- migrated */
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p->se.avg.last_update_time = 0;
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#endif
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se->depth = se->parent ? se->parent->depth + 1 : 0;
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cfs_rq = cfs_rq_of(se);
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if (!queued)
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se->vruntime += cfs_rq->min_vruntime;
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/* Virtually synchronize task with its new cfs_rq */
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attach_entity_load_avg(cfs_rq, se);
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attach_task_cfs_rq(p);
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}
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void free_fair_sched_group(struct task_group *tg)
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