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Commit a790de99 authored by Paul Turner's avatar Paul Turner Committed by Ingo Molnar
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sched: Validate CFS quota hierarchies 



Add constraints validation for CFS bandwidth hierarchies.

Validate that:
   max(child bandwidth) <= parent_bandwidth

In a quota limited hierarchy, an unconstrained entity
(e.g. bandwidth==RUNTIME_INF) inherits the bandwidth of its parent.

This constraint is chosen over sum(child_bandwidth) as notion of over-commit is
valuable within SCHED_OTHER.  Some basic code from the RT case is re-factored
for reuse.

Signed-off-by: default avatarPaul Turner <pjt@google.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.083774572@google.com


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent ab84d31e

kernel/sched.c

+98 −14
Original line number Diff line number Diff line
@@ -252,6 +252,7 @@ struct cfs_bandwidth { 
	raw_spinlock_t lock;

	ktime_t period;

	u64 quota;

	s64 hierarchal_quota;

#endif

};
@@ -1518,7 +1519,8 @@ static inline void dec_cpu_load(struct rq *rq, unsigned long load) 
	update_load_sub(&rq->load, load);

}



#if (defined(CONFIG_SMP) && defined(CONFIG_FAIR_GROUP_SCHED)) || defined(CONFIG_RT_GROUP_SCHED)

#if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \

			(defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))

typedef int (*tg_visitor)(struct task_group *, void *);



/*
@@ -8708,12 +8710,7 @@ unsigned long sched_group_shares(struct task_group *tg) 
}

#endif



#ifdef CONFIG_RT_GROUP_SCHED

/*

 * Ensure that the real time constraints are schedulable.

 */

static DEFINE_MUTEX(rt_constraints_mutex);



#if defined(CONFIG_RT_GROUP_SCHED) || defined(CONFIG_CFS_BANDWIDTH)

static unsigned long to_ratio(u64 period, u64 runtime)

{

	if (runtime == RUNTIME_INF)
@@ -8721,6 +8718,13 @@ static unsigned long to_ratio(u64 period, u64 runtime) 


	return div64_u64(runtime << 20, period);

}

#endif



#ifdef CONFIG_RT_GROUP_SCHED

/*

 * Ensure that the real time constraints are schedulable.

 */

static DEFINE_MUTEX(rt_constraints_mutex);



/* Must be called with tasklist_lock held */

static inline int tg_has_rt_tasks(struct task_group *tg)
@@ -8741,7 +8745,7 @@ struct rt_schedulable_data { 
	u64 rt_runtime;

};



static int tg_schedulable(struct task_group *tg, void *data)

static int tg_rt_schedulable(struct task_group *tg, void *data)

{

	struct rt_schedulable_data *d = data;

	struct task_group *child;
@@ -8805,7 +8809,7 @@ static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime) 
		.rt_runtime = runtime,

	};



	return walk_tg_tree(tg_schedulable, tg_nop, &data);

	return walk_tg_tree(tg_rt_schedulable, tg_nop, &data);

}



static int tg_set_rt_bandwidth(struct task_group *tg,
@@ -9064,14 +9068,17 @@ static u64 cpu_shares_read_u64(struct cgroup *cgrp, struct cftype *cft) 
}



#ifdef CONFIG_CFS_BANDWIDTH

static DEFINE_MUTEX(cfs_constraints_mutex);



const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */

const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */



static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);



static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)

{

	int i;

	int i, ret = 0;

	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);

	static DEFINE_MUTEX(mutex);



	if (tg == &root_task_group)

		return -EINVAL;
@@ -9092,7 +9099,11 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota) 
	if (period > max_cfs_quota_period)

		return -EINVAL;



	mutex_lock(&mutex);

	mutex_lock(&cfs_constraints_mutex);

	ret = __cfs_schedulable(tg, period, quota);

	if (ret)

		goto out_unlock;



	raw_spin_lock_irq(&cfs_b->lock);

	cfs_b->period = ns_to_ktime(period);

	cfs_b->quota = quota;
@@ -9107,9 +9118,10 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota) 
		cfs_rq->runtime_remaining = 0;

		raw_spin_unlock_irq(&rq->lock);

	}

	mutex_unlock(&mutex);

out_unlock:

	mutex_unlock(&cfs_constraints_mutex);



	return 0;

	return ret;

}



int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
@@ -9183,6 +9195,78 @@ static int cpu_cfs_period_write_u64(struct cgroup *cgrp, struct cftype *cftype, 
	return tg_set_cfs_period(cgroup_tg(cgrp), cfs_period_us);

}



struct cfs_schedulable_data {

	struct task_group *tg;

	u64 period, quota;

};



/*

 * normalize group quota/period to be quota/max_period

 * note: units are usecs

 */

static u64 normalize_cfs_quota(struct task_group *tg,

			       struct cfs_schedulable_data *d)

{

	u64 quota, period;



	if (tg == d->tg) {

		period = d->period;

		quota = d->quota;

	} else {

		period = tg_get_cfs_period(tg);

		quota = tg_get_cfs_quota(tg);

	}



	/* note: these should typically be equivalent */

	if (quota == RUNTIME_INF || quota == -1)

		return RUNTIME_INF;



	return to_ratio(period, quota);

}



static int tg_cfs_schedulable_down(struct task_group *tg, void *data)

{

	struct cfs_schedulable_data *d = data;

	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);

	s64 quota = 0, parent_quota = -1;



	if (!tg->parent) {

		quota = RUNTIME_INF;

	} else {

		struct cfs_bandwidth *parent_b = tg_cfs_bandwidth(tg->parent);



		quota = normalize_cfs_quota(tg, d);

		parent_quota = parent_b->hierarchal_quota;



		/*

		 * ensure max(child_quota) <= parent_quota, inherit when no

		 * limit is set

		 */

		if (quota == RUNTIME_INF)

			quota = parent_quota;

		else if (parent_quota != RUNTIME_INF && quota > parent_quota)

			return -EINVAL;

	}

	cfs_b->hierarchal_quota = quota;



	return 0;

}



static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)

{

	struct cfs_schedulable_data data = {

		.tg = tg,

		.period = period,

		.quota = quota,

	};



	if (quota != RUNTIME_INF) {

		do_div(data.period, NSEC_PER_USEC);

		do_div(data.quota, NSEC_PER_USEC);

	}



	return walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);

}

#endif /* CONFIG_CFS_BANDWIDTH */

#endif /* CONFIG_FAIR_GROUP_SCHED */