sched: Introduce primitives to account for CFS bandwidth tracking
In this patch we introduce the notion of CFS bandwidth, partitioned into globally unassigned bandwidth, and locally claimed bandwidth. - The global bandwidth is per task_group, it represents a pool of unclaimed bandwidth that cfs_rqs can allocate from. - The local bandwidth is tracked per-cfs_rq, this represents allotments from the global pool bandwidth assigned to a specific cpu. Bandwidth is managed via cgroupfs, adding two new interfaces to the cpu subsystem: - cpu.cfs_period_us : the bandwidth period in usecs - cpu.cfs_quota_us : the cpu bandwidth (in usecs) that this tg will be allowed to consume over period above. Signed-off-by: Paul Turner <pjt@google.com> Signed-off-by: Nikhil Rao <ncrao@google.com> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20110721184756.972636699@google.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Paul Turner
Ingo Molnar
196
kernel/sched.c
196
kernel/sched.c
@@ -247,6 +247,14 @@ struct cfs_rq;
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static LIST_HEAD(task_groups);
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struct cfs_bandwidth {
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#ifdef CONFIG_CFS_BANDWIDTH
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raw_spinlock_t lock;
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ktime_t period;
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u64 quota;
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#endif
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};
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/* task group related information */
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struct task_group {
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struct cgroup_subsys_state css;
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@@ -278,6 +286,8 @@ struct task_group {
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#ifdef CONFIG_SCHED_AUTOGROUP
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struct autogroup *autogroup;
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#endif
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struct cfs_bandwidth cfs_bandwidth;
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};
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/* task_group_lock serializes the addition/removal of task groups */
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@@ -377,9 +387,48 @@ struct cfs_rq {
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unsigned long load_contribution;
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#endif
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#ifdef CONFIG_CFS_BANDWIDTH
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int runtime_enabled;
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s64 runtime_remaining;
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#endif
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#endif
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};
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#ifdef CONFIG_FAIR_GROUP_SCHED
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#ifdef CONFIG_CFS_BANDWIDTH
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static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
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{
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return &tg->cfs_bandwidth;
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}
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static inline u64 default_cfs_period(void);
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static void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
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{
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raw_spin_lock_init(&cfs_b->lock);
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cfs_b->quota = RUNTIME_INF;
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cfs_b->period = ns_to_ktime(default_cfs_period());
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}
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static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
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{
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cfs_rq->runtime_enabled = 0;
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}
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static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
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{}
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#else
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static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
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static void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
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static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
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static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
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{
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return NULL;
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}
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#endif /* CONFIG_CFS_BANDWIDTH */
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#endif /* CONFIG_FAIR_GROUP_SCHED */
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/* Real-Time classes' related field in a runqueue: */
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struct rt_rq {
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struct rt_prio_array active;
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@@ -7971,6 +8020,7 @@ static void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
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/* allow initial update_cfs_load() to truncate */
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cfs_rq->load_stamp = 1;
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#endif
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init_cfs_rq_runtime(cfs_rq);
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tg->cfs_rq[cpu] = cfs_rq;
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tg->se[cpu] = se;
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@@ -8110,6 +8160,7 @@ void __init sched_init(void)
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* We achieve this by letting root_task_group's tasks sit
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* directly in rq->cfs (i.e root_task_group->se[] = NULL).
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*/
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init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
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init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
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#endif /* CONFIG_FAIR_GROUP_SCHED */
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@@ -8351,6 +8402,8 @@ static void free_fair_sched_group(struct task_group *tg)
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{
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int i;
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destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
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for_each_possible_cpu(i) {
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if (tg->cfs_rq)
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kfree(tg->cfs_rq[i]);
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@@ -8378,6 +8431,8 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
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tg->shares = NICE_0_LOAD;
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init_cfs_bandwidth(tg_cfs_bandwidth(tg));
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for_each_possible_cpu(i) {
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cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
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GFP_KERNEL, cpu_to_node(i));
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@@ -8753,7 +8808,7 @@ static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
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return walk_tg_tree(tg_schedulable, tg_nop, &data);
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}
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static int tg_set_bandwidth(struct task_group *tg,
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static int tg_set_rt_bandwidth(struct task_group *tg,
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u64 rt_period, u64 rt_runtime)
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{
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int i, err = 0;
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@@ -8792,7 +8847,7 @@ int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
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if (rt_runtime_us < 0)
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rt_runtime = RUNTIME_INF;
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return tg_set_bandwidth(tg, rt_period, rt_runtime);
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return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
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}
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long sched_group_rt_runtime(struct task_group *tg)
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@@ -8817,7 +8872,7 @@ int sched_group_set_rt_period(struct task_group *tg, long rt_period_us)
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if (rt_period == 0)
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return -EINVAL;
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return tg_set_bandwidth(tg, rt_period, rt_runtime);
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return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
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}
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long sched_group_rt_period(struct task_group *tg)
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@@ -9007,6 +9062,128 @@ static u64 cpu_shares_read_u64(struct cgroup *cgrp, struct cftype *cft)
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return (u64) scale_load_down(tg->shares);
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}
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#ifdef CONFIG_CFS_BANDWIDTH
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const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
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const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
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static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
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{
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int i;
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struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
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static DEFINE_MUTEX(mutex);
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if (tg == &root_task_group)
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return -EINVAL;
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/*
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* Ensure we have at some amount of bandwidth every period. This is
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* to prevent reaching a state of large arrears when throttled via
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* entity_tick() resulting in prolonged exit starvation.
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*/
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if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
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return -EINVAL;
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/*
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* Likewise, bound things on the otherside by preventing insane quota
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* periods. This also allows us to normalize in computing quota
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* feasibility.
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*/
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if (period > max_cfs_quota_period)
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return -EINVAL;
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mutex_lock(&mutex);
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raw_spin_lock_irq(&cfs_b->lock);
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cfs_b->period = ns_to_ktime(period);
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cfs_b->quota = quota;
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raw_spin_unlock_irq(&cfs_b->lock);
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for_each_possible_cpu(i) {
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struct cfs_rq *cfs_rq = tg->cfs_rq[i];
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struct rq *rq = rq_of(cfs_rq);
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raw_spin_lock_irq(&rq->lock);
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cfs_rq->runtime_enabled = quota != RUNTIME_INF;
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cfs_rq->runtime_remaining = 0;
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raw_spin_unlock_irq(&rq->lock);
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}
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mutex_unlock(&mutex);
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return 0;
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}
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int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
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{
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u64 quota, period;
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period = ktime_to_ns(tg_cfs_bandwidth(tg)->period);
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if (cfs_quota_us < 0)
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quota = RUNTIME_INF;
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else
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quota = (u64)cfs_quota_us * NSEC_PER_USEC;
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return tg_set_cfs_bandwidth(tg, period, quota);
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}
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long tg_get_cfs_quota(struct task_group *tg)
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{
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u64 quota_us;
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if (tg_cfs_bandwidth(tg)->quota == RUNTIME_INF)
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return -1;
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quota_us = tg_cfs_bandwidth(tg)->quota;
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do_div(quota_us, NSEC_PER_USEC);
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return quota_us;
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}
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int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
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{
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u64 quota, period;
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period = (u64)cfs_period_us * NSEC_PER_USEC;
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quota = tg_cfs_bandwidth(tg)->quota;
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if (period <= 0)
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return -EINVAL;
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return tg_set_cfs_bandwidth(tg, period, quota);
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}
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long tg_get_cfs_period(struct task_group *tg)
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{
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u64 cfs_period_us;
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cfs_period_us = ktime_to_ns(tg_cfs_bandwidth(tg)->period);
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do_div(cfs_period_us, NSEC_PER_USEC);
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return cfs_period_us;
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}
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static s64 cpu_cfs_quota_read_s64(struct cgroup *cgrp, struct cftype *cft)
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{
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return tg_get_cfs_quota(cgroup_tg(cgrp));
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}
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static int cpu_cfs_quota_write_s64(struct cgroup *cgrp, struct cftype *cftype,
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s64 cfs_quota_us)
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{
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return tg_set_cfs_quota(cgroup_tg(cgrp), cfs_quota_us);
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}
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static u64 cpu_cfs_period_read_u64(struct cgroup *cgrp, struct cftype *cft)
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{
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return tg_get_cfs_period(cgroup_tg(cgrp));
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}
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static int cpu_cfs_period_write_u64(struct cgroup *cgrp, struct cftype *cftype,
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u64 cfs_period_us)
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{
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return tg_set_cfs_period(cgroup_tg(cgrp), cfs_period_us);
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}
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#endif /* CONFIG_CFS_BANDWIDTH */
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#endif /* CONFIG_FAIR_GROUP_SCHED */
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#ifdef CONFIG_RT_GROUP_SCHED
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@@ -9041,6 +9218,18 @@ static struct cftype cpu_files[] = {
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.write_u64 = cpu_shares_write_u64,
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},
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#endif
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#ifdef CONFIG_CFS_BANDWIDTH
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{
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.name = "cfs_quota_us",
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.read_s64 = cpu_cfs_quota_read_s64,
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.write_s64 = cpu_cfs_quota_write_s64,
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},
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{
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.name = "cfs_period_us",
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.read_u64 = cpu_cfs_period_read_u64,
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.write_u64 = cpu_cfs_period_write_u64,
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},
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#endif
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#ifdef CONFIG_RT_GROUP_SCHED
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{
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.name = "rt_runtime_us",
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@@ -9350,4 +9539,3 @@ struct cgroup_subsys cpuacct_subsys = {
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.subsys_id = cpuacct_subsys_id,
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};
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#endif /* CONFIG_CGROUP_CPUACCT */
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@@ -1234,6 +1234,22 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
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check_preempt_tick(cfs_rq, curr);
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}
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/**************************************************
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* CFS bandwidth control machinery
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*/
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#ifdef CONFIG_CFS_BANDWIDTH
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/*
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* default period for cfs group bandwidth.
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* default: 0.1s, units: nanoseconds
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*/
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static inline u64 default_cfs_period(void)
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{
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return 100000000ULL;
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}
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#endif
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/**************************************************
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* CFS operations on tasks:
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*/
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