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: Paul Turner --- kernel/sched.c | 109 ++++++++++++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 96 insertions(+), 13 deletions(-) Index: tip/kernel/sched.c =================================================================== --- tip.orig/kernel/sched.c +++ tip/kernel/sched.c @@ -249,6 +249,7 @@ struct cfs_bandwidth { raw_spinlock_t lock; ktime_t period; u64 quota; + s64 hierarchal_quota; #endif }; @@ -8534,12 +8535,7 @@ unsigned long sched_group_shares(struct } #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) @@ -8547,6 +8543,13 @@ static unsigned long to_ratio(u64 period 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) @@ -8567,7 +8570,7 @@ 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; @@ -8631,7 +8634,7 @@ static int __rt_schedulable(struct task_ .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, @@ -8890,14 +8893,17 @@ static u64 cpu_shares_read_u64(struct cg } #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; @@ -8918,7 +8924,11 @@ static int tg_set_cfs_bandwidth(struct t 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; @@ -8933,9 +8943,10 @@ static int tg_set_cfs_bandwidth(struct t 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) @@ -9009,6 +9020,78 @@ static int cpu_cfs_period_write_u64(stru 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 */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/