3711 lines
94 KiB
C
3711 lines
94 KiB
C
/*
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* Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
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*
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* Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
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*
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* Interactivity improvements by Mike Galbraith
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* (C) 2007 Mike Galbraith <efault@gmx.de>
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*
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* Various enhancements by Dmitry Adamushko.
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* (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
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*
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* Group scheduling enhancements by Srivatsa Vaddagiri
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* Copyright IBM Corporation, 2007
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* Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
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*
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* Scaled math optimizations by Thomas Gleixner
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* Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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*
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* Adaptive scheduling granularity, math enhancements by Peter Zijlstra
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* Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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*/
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#include <linux/latencytop.h>
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#include <linux/sched.h>
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/*
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* Targeted preemption latency for CPU-bound tasks:
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* (default: 5ms * (1 + ilog(ncpus)), units: nanoseconds)
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*
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* NOTE: this latency value is not the same as the concept of
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* 'timeslice length' - timeslices in CFS are of variable length
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* and have no persistent notion like in traditional, time-slice
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* based scheduling concepts.
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*
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* (to see the precise effective timeslice length of your workload,
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* run vmstat and monitor the context-switches (cs) field)
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*/
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unsigned int sysctl_sched_latency = 5000000ULL;
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unsigned int normalized_sysctl_sched_latency = 5000000ULL;
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/*
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* The initial- and re-scaling of tunables is configurable
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* (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
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*
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* Options are:
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* SCHED_TUNABLESCALING_NONE - unscaled, always *1
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* SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
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* SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
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*/
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enum sched_tunable_scaling sysctl_sched_tunable_scaling
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= SCHED_TUNABLESCALING_LOG;
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/*
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* Minimal preemption granularity for CPU-bound tasks:
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* (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
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*/
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unsigned int sysctl_sched_min_granularity = 1000000ULL;
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unsigned int normalized_sysctl_sched_min_granularity = 1000000ULL;
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/*
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* is kept at sysctl_sched_latency / sysctl_sched_min_granularity
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*/
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static unsigned int sched_nr_latency = 5;
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/*
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* After fork, child runs first. If set to 0 (default) then
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* parent will (try to) run first.
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*/
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unsigned int sysctl_sched_child_runs_first __read_mostly;
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/*
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* sys_sched_yield() compat mode
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*
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* This option switches the agressive yield implementation of the
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* old scheduler back on.
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*/
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unsigned int __read_mostly sysctl_sched_compat_yield;
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/*
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* SCHED_OTHER wake-up granularity.
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* (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
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*
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* This option delays the preemption effects of decoupled workloads
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* and reduces their over-scheduling. Synchronous workloads will still
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* have immediate wakeup/sleep latencies.
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*/
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unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
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unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
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const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
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static const struct sched_class fair_sched_class;
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/**************************************************************
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* CFS operations on generic schedulable entities:
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*/
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#ifdef CONFIG_FAIR_GROUP_SCHED
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/* cpu runqueue to which this cfs_rq is attached */
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
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{
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return cfs_rq->rq;
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}
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/* An entity is a task if it doesn't "own" a runqueue */
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#define entity_is_task(se) (!se->my_q)
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static inline struct task_struct *task_of(struct sched_entity *se)
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{
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#ifdef CONFIG_SCHED_DEBUG
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WARN_ON_ONCE(!entity_is_task(se));
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#endif
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return container_of(se, struct task_struct, se);
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}
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/* Walk up scheduling entities hierarchy */
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#define for_each_sched_entity(se) \
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for (; se; se = se->parent)
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static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
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{
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return p->se.cfs_rq;
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}
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/* runqueue on which this entity is (to be) queued */
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static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
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{
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return se->cfs_rq;
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}
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/* runqueue "owned" by this group */
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static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
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{
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return grp->my_q;
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}
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/* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on
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* another cpu ('this_cpu')
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*/
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static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
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{
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return cfs_rq->tg->cfs_rq[this_cpu];
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}
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/* Iterate thr' all leaf cfs_rq's on a runqueue */
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#define for_each_leaf_cfs_rq(rq, cfs_rq) \
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list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
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/* Do the two (enqueued) entities belong to the same group ? */
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static inline int
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is_same_group(struct sched_entity *se, struct sched_entity *pse)
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{
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if (se->cfs_rq == pse->cfs_rq)
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return 1;
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return 0;
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}
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static inline struct sched_entity *parent_entity(struct sched_entity *se)
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{
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return se->parent;
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}
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/* return depth at which a sched entity is present in the hierarchy */
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static inline int depth_se(struct sched_entity *se)
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{
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int depth = 0;
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for_each_sched_entity(se)
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depth++;
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return depth;
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}
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static void
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find_matching_se(struct sched_entity **se, struct sched_entity **pse)
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{
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int se_depth, pse_depth;
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/*
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* preemption test can be made between sibling entities who are in the
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* same cfs_rq i.e who have a common parent. Walk up the hierarchy of
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* both tasks until we find their ancestors who are siblings of common
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* parent.
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*/
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/* First walk up until both entities are at same depth */
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se_depth = depth_se(*se);
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pse_depth = depth_se(*pse);
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while (se_depth > pse_depth) {
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se_depth--;
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*se = parent_entity(*se);
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}
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while (pse_depth > se_depth) {
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pse_depth--;
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*pse = parent_entity(*pse);
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}
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while (!is_same_group(*se, *pse)) {
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*se = parent_entity(*se);
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*pse = parent_entity(*pse);
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}
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}
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#else /* !CONFIG_FAIR_GROUP_SCHED */
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static inline struct task_struct *task_of(struct sched_entity *se)
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{
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return container_of(se, struct task_struct, se);
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}
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
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{
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return container_of(cfs_rq, struct rq, cfs);
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}
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#define entity_is_task(se) 1
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#define for_each_sched_entity(se) \
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for (; se; se = NULL)
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static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
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{
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return &task_rq(p)->cfs;
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}
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static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
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{
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struct task_struct *p = task_of(se);
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struct rq *rq = task_rq(p);
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return &rq->cfs;
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}
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/* runqueue "owned" by this group */
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static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
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{
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return NULL;
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}
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static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
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{
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return &cpu_rq(this_cpu)->cfs;
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}
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#define for_each_leaf_cfs_rq(rq, cfs_rq) \
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for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
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static inline int
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is_same_group(struct sched_entity *se, struct sched_entity *pse)
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{
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return 1;
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}
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static inline struct sched_entity *parent_entity(struct sched_entity *se)
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{
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return NULL;
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}
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static inline void
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find_matching_se(struct sched_entity **se, struct sched_entity **pse)
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{
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}
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#endif /* CONFIG_FAIR_GROUP_SCHED */
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/**************************************************************
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* Scheduling class tree data structure manipulation methods:
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*/
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static inline u64 max_vruntime(u64 min_vruntime, u64 vruntime)
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{
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s64 delta = (s64)(vruntime - min_vruntime);
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if (delta > 0)
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min_vruntime = vruntime;
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return min_vruntime;
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}
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static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
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{
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s64 delta = (s64)(vruntime - min_vruntime);
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if (delta < 0)
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min_vruntime = vruntime;
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return min_vruntime;
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}
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static inline int entity_before(struct sched_entity *a,
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struct sched_entity *b)
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{
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return (s64)(a->vruntime - b->vruntime) < 0;
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}
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static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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return se->vruntime - cfs_rq->min_vruntime;
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}
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static void update_min_vruntime(struct cfs_rq *cfs_rq)
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{
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u64 vruntime = cfs_rq->min_vruntime;
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if (cfs_rq->curr)
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vruntime = cfs_rq->curr->vruntime;
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if (cfs_rq->rb_leftmost) {
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struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
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struct sched_entity,
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run_node);
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if (!cfs_rq->curr)
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vruntime = se->vruntime;
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else
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vruntime = min_vruntime(vruntime, se->vruntime);
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}
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cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
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}
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/*
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* Enqueue an entity into the rb-tree:
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*/
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static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
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struct rb_node *parent = NULL;
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struct sched_entity *entry;
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s64 key = entity_key(cfs_rq, se);
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int leftmost = 1;
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/*
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* Find the right place in the rbtree:
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*/
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while (*link) {
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parent = *link;
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entry = rb_entry(parent, struct sched_entity, run_node);
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/*
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* We dont care about collisions. Nodes with
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* the same key stay together.
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*/
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if (key < entity_key(cfs_rq, entry)) {
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link = &parent->rb_left;
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} else {
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link = &parent->rb_right;
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leftmost = 0;
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}
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}
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/*
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* Maintain a cache of leftmost tree entries (it is frequently
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* used):
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*/
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if (leftmost)
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cfs_rq->rb_leftmost = &se->run_node;
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rb_link_node(&se->run_node, parent, link);
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rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
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}
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static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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if (cfs_rq->rb_leftmost == &se->run_node) {
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struct rb_node *next_node;
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next_node = rb_next(&se->run_node);
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cfs_rq->rb_leftmost = next_node;
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}
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rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
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}
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static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
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{
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struct rb_node *left = cfs_rq->rb_leftmost;
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if (!left)
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return NULL;
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return rb_entry(left, struct sched_entity, run_node);
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}
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static struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
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{
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struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
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if (!last)
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return NULL;
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return rb_entry(last, struct sched_entity, run_node);
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}
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/**************************************************************
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* Scheduling class statistics methods:
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*/
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#ifdef CONFIG_SCHED_DEBUG
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int sched_proc_update_handler(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos)
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{
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int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
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int factor = get_update_sysctl_factor();
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if (ret || !write)
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return ret;
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sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
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sysctl_sched_min_granularity);
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#define WRT_SYSCTL(name) \
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(normalized_sysctl_##name = sysctl_##name / (factor))
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WRT_SYSCTL(sched_min_granularity);
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WRT_SYSCTL(sched_latency);
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WRT_SYSCTL(sched_wakeup_granularity);
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WRT_SYSCTL(sched_shares_ratelimit);
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#undef WRT_SYSCTL
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return 0;
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}
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#endif
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/*
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* delta /= w
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*/
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static inline unsigned long
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calc_delta_fair(unsigned long delta, struct sched_entity *se)
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{
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if (unlikely(se->load.weight != NICE_0_LOAD))
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delta = calc_delta_mine(delta, NICE_0_LOAD, &se->load);
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return delta;
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}
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/*
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* The idea is to set a period in which each task runs once.
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*
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* When there are too many tasks (sysctl_sched_nr_latency) we have to stretch
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* this period because otherwise the slices get too small.
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*
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* p = (nr <= nl) ? l : l*nr/nl
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*/
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static u64 __sched_period(unsigned long nr_running)
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{
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u64 period = sysctl_sched_latency;
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unsigned long nr_latency = sched_nr_latency;
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if (unlikely(nr_running > nr_latency)) {
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period = sysctl_sched_min_granularity;
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period *= nr_running;
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}
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return period;
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}
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/*
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* We calculate the wall-time slice from the period by taking a part
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* proportional to the weight.
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*
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* s = p*P[w/rw]
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*/
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static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
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for_each_sched_entity(se) {
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struct load_weight *load;
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struct load_weight lw;
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cfs_rq = cfs_rq_of(se);
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load = &cfs_rq->load;
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if (unlikely(!se->on_rq)) {
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lw = cfs_rq->load;
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update_load_add(&lw, se->load.weight);
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load = &lw;
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}
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slice = calc_delta_mine(slice, se->load.weight, load);
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}
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return slice;
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}
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|
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/*
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* We calculate the vruntime slice of a to be inserted task
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*
|
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* vs = s/w
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*/
|
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static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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return calc_delta_fair(sched_slice(cfs_rq, se), se);
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}
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|
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/*
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* Update the current task's runtime statistics. Skip current tasks that
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* are not in our scheduling class.
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*/
|
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static inline void
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__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
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unsigned long delta_exec)
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{
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unsigned long delta_exec_weighted;
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schedstat_set(curr->exec_max, max((u64)delta_exec, curr->exec_max));
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|
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curr->sum_exec_runtime += delta_exec;
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schedstat_add(cfs_rq, exec_clock, delta_exec);
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delta_exec_weighted = calc_delta_fair(delta_exec, curr);
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|
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curr->vruntime += delta_exec_weighted;
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update_min_vruntime(cfs_rq);
|
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}
|
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|
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static void update_curr(struct cfs_rq *cfs_rq)
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{
|
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struct sched_entity *curr = cfs_rq->curr;
|
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u64 now = rq_of(cfs_rq)->clock;
|
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unsigned long delta_exec;
|
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|
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if (unlikely(!curr))
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return;
|
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|
|
/*
|
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* Get the amount of time the current task was running
|
|
* since the last time we changed load (this cannot
|
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* overflow on 32 bits):
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|
*/
|
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delta_exec = (unsigned long)(now - curr->exec_start);
|
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if (!delta_exec)
|
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return;
|
|
|
|
__update_curr(cfs_rq, curr, delta_exec);
|
|
curr->exec_start = now;
|
|
|
|
if (entity_is_task(curr)) {
|
|
struct task_struct *curtask = task_of(curr);
|
|
|
|
trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
|
|
cpuacct_charge(curtask, delta_exec);
|
|
account_group_exec_runtime(curtask, delta_exec);
|
|
}
|
|
}
|
|
|
|
static inline void
|
|
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
schedstat_set(se->wait_start, rq_of(cfs_rq)->clock);
|
|
}
|
|
|
|
/*
|
|
* Task is being enqueued - update stats:
|
|
*/
|
|
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
/*
|
|
* Are we enqueueing a waiting task? (for current tasks
|
|
* a dequeue/enqueue event is a NOP)
|
|
*/
|
|
if (se != cfs_rq->curr)
|
|
update_stats_wait_start(cfs_rq, se);
|
|
}
|
|
|
|
static void
|
|
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
schedstat_set(se->wait_max, max(se->wait_max,
|
|
rq_of(cfs_rq)->clock - se->wait_start));
|
|
schedstat_set(se->wait_count, se->wait_count + 1);
|
|
schedstat_set(se->wait_sum, se->wait_sum +
|
|
rq_of(cfs_rq)->clock - se->wait_start);
|
|
#ifdef CONFIG_SCHEDSTATS
|
|
if (entity_is_task(se)) {
|
|
trace_sched_stat_wait(task_of(se),
|
|
rq_of(cfs_rq)->clock - se->wait_start);
|
|
}
|
|
#endif
|
|
schedstat_set(se->wait_start, 0);
|
|
}
|
|
|
|
static inline void
|
|
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
/*
|
|
* Mark the end of the wait period if dequeueing a
|
|
* waiting task:
|
|
*/
|
|
if (se != cfs_rq->curr)
|
|
update_stats_wait_end(cfs_rq, se);
|
|
}
|
|
|
|
/*
|
|
* We are picking a new current task - update its stats:
|
|
*/
|
|
static inline void
|
|
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
/*
|
|
* We are starting a new run period:
|
|
*/
|
|
se->exec_start = rq_of(cfs_rq)->clock;
|
|
}
|
|
|
|
/**************************************************
|
|
* Scheduling class queueing methods:
|
|
*/
|
|
|
|
#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
|
|
static void
|
|
add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight)
|
|
{
|
|
cfs_rq->task_weight += weight;
|
|
}
|
|
#else
|
|
static inline void
|
|
add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight)
|
|
{
|
|
}
|
|
#endif
|
|
|
|
static void
|
|
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
update_load_add(&cfs_rq->load, se->load.weight);
|
|
if (!parent_entity(se))
|
|
inc_cpu_load(rq_of(cfs_rq), se->load.weight);
|
|
if (entity_is_task(se)) {
|
|
add_cfs_task_weight(cfs_rq, se->load.weight);
|
|
list_add(&se->group_node, &cfs_rq->tasks);
|
|
}
|
|
cfs_rq->nr_running++;
|
|
se->on_rq = 1;
|
|
}
|
|
|
|
static void
|
|
account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
update_load_sub(&cfs_rq->load, se->load.weight);
|
|
if (!parent_entity(se))
|
|
dec_cpu_load(rq_of(cfs_rq), se->load.weight);
|
|
if (entity_is_task(se)) {
|
|
add_cfs_task_weight(cfs_rq, -se->load.weight);
|
|
list_del_init(&se->group_node);
|
|
}
|
|
cfs_rq->nr_running--;
|
|
se->on_rq = 0;
|
|
}
|
|
|
|
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
#ifdef CONFIG_SCHEDSTATS
|
|
struct task_struct *tsk = NULL;
|
|
|
|
if (entity_is_task(se))
|
|
tsk = task_of(se);
|
|
|
|
if (se->sleep_start) {
|
|
u64 delta = rq_of(cfs_rq)->clock - se->sleep_start;
|
|
|
|
if ((s64)delta < 0)
|
|
delta = 0;
|
|
|
|
if (unlikely(delta > se->sleep_max))
|
|
se->sleep_max = delta;
|
|
|
|
se->sleep_start = 0;
|
|
se->sum_sleep_runtime += delta;
|
|
|
|
if (tsk) {
|
|
account_scheduler_latency(tsk, delta >> 10, 1);
|
|
trace_sched_stat_sleep(tsk, delta);
|
|
}
|
|
}
|
|
if (se->block_start) {
|
|
u64 delta = rq_of(cfs_rq)->clock - se->block_start;
|
|
|
|
if ((s64)delta < 0)
|
|
delta = 0;
|
|
|
|
if (unlikely(delta > se->block_max))
|
|
se->block_max = delta;
|
|
|
|
se->block_start = 0;
|
|
se->sum_sleep_runtime += delta;
|
|
|
|
if (tsk) {
|
|
if (tsk->in_iowait) {
|
|
se->iowait_sum += delta;
|
|
se->iowait_count++;
|
|
trace_sched_stat_iowait(tsk, delta);
|
|
}
|
|
|
|
/*
|
|
* Blocking time is in units of nanosecs, so shift by
|
|
* 20 to get a milliseconds-range estimation of the
|
|
* amount of time that the task spent sleeping:
|
|
*/
|
|
if (unlikely(prof_on == SLEEP_PROFILING)) {
|
|
profile_hits(SLEEP_PROFILING,
|
|
(void *)get_wchan(tsk),
|
|
delta >> 20);
|
|
}
|
|
account_scheduler_latency(tsk, delta >> 10, 0);
|
|
}
|
|
}
|
|
#endif
|
|
}
|
|
|
|
static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
#ifdef CONFIG_SCHED_DEBUG
|
|
s64 d = se->vruntime - cfs_rq->min_vruntime;
|
|
|
|
if (d < 0)
|
|
d = -d;
|
|
|
|
if (d > 3*sysctl_sched_latency)
|
|
schedstat_inc(cfs_rq, nr_spread_over);
|
|
#endif
|
|
}
|
|
|
|
static void
|
|
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
|
|
{
|
|
u64 vruntime = cfs_rq->min_vruntime;
|
|
|
|
/*
|
|
* The 'current' period is already promised to the current tasks,
|
|
* however the extra weight of the new task will slow them down a
|
|
* little, place the new task so that it fits in the slot that
|
|
* stays open at the end.
|
|
*/
|
|
if (initial && sched_feat(START_DEBIT))
|
|
vruntime += sched_vslice(cfs_rq, se);
|
|
|
|
/* sleeps up to a single latency don't count. */
|
|
if (!initial && sched_feat(FAIR_SLEEPERS)) {
|
|
unsigned long thresh = sysctl_sched_latency;
|
|
|
|
/*
|
|
* Convert the sleeper threshold into virtual time.
|
|
* SCHED_IDLE is a special sub-class. We care about
|
|
* fairness only relative to other SCHED_IDLE tasks,
|
|
* all of which have the same weight.
|
|
*/
|
|
if (sched_feat(NORMALIZED_SLEEPER) && (!entity_is_task(se) ||
|
|
task_of(se)->policy != SCHED_IDLE))
|
|
thresh = calc_delta_fair(thresh, se);
|
|
|
|
/*
|
|
* Halve their sleep time's effect, to allow
|
|
* for a gentler effect of sleepers:
|
|
*/
|
|
if (sched_feat(GENTLE_FAIR_SLEEPERS))
|
|
thresh >>= 1;
|
|
|
|
vruntime -= thresh;
|
|
}
|
|
|
|
/* ensure we never gain time by being placed backwards. */
|
|
vruntime = max_vruntime(se->vruntime, vruntime);
|
|
|
|
se->vruntime = vruntime;
|
|
}
|
|
|
|
#define ENQUEUE_WAKEUP 1
|
|
#define ENQUEUE_MIGRATE 2
|
|
|
|
static void
|
|
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
|
|
{
|
|
/*
|
|
* Update the normalized vruntime before updating min_vruntime
|
|
* through callig update_curr().
|
|
*/
|
|
if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATE))
|
|
se->vruntime += cfs_rq->min_vruntime;
|
|
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
account_entity_enqueue(cfs_rq, se);
|
|
|
|
if (flags & ENQUEUE_WAKEUP) {
|
|
place_entity(cfs_rq, se, 0);
|
|
enqueue_sleeper(cfs_rq, se);
|
|
}
|
|
|
|
update_stats_enqueue(cfs_rq, se);
|
|
check_spread(cfs_rq, se);
|
|
if (se != cfs_rq->curr)
|
|
__enqueue_entity(cfs_rq, se);
|
|
}
|
|
|
|
static void __clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
if (!se || cfs_rq->last == se)
|
|
cfs_rq->last = NULL;
|
|
|
|
if (!se || cfs_rq->next == se)
|
|
cfs_rq->next = NULL;
|
|
}
|
|
|
|
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
for_each_sched_entity(se)
|
|
__clear_buddies(cfs_rq_of(se), se);
|
|
}
|
|
|
|
static void
|
|
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
|
|
{
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
|
|
update_stats_dequeue(cfs_rq, se);
|
|
if (sleep) {
|
|
#ifdef CONFIG_SCHEDSTATS
|
|
if (entity_is_task(se)) {
|
|
struct task_struct *tsk = task_of(se);
|
|
|
|
if (tsk->state & TASK_INTERRUPTIBLE)
|
|
se->sleep_start = rq_of(cfs_rq)->clock;
|
|
if (tsk->state & TASK_UNINTERRUPTIBLE)
|
|
se->block_start = rq_of(cfs_rq)->clock;
|
|
}
|
|
#endif
|
|
}
|
|
|
|
clear_buddies(cfs_rq, se);
|
|
|
|
if (se != cfs_rq->curr)
|
|
__dequeue_entity(cfs_rq, se);
|
|
account_entity_dequeue(cfs_rq, se);
|
|
update_min_vruntime(cfs_rq);
|
|
|
|
/*
|
|
* Normalize the entity after updating the min_vruntime because the
|
|
* update can refer to the ->curr item and we need to reflect this
|
|
* movement in our normalized position.
|
|
*/
|
|
if (!sleep)
|
|
se->vruntime -= cfs_rq->min_vruntime;
|
|
}
|
|
|
|
/*
|
|
* Preempt the current task with a newly woken task if needed:
|
|
*/
|
|
static void
|
|
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
|
|
{
|
|
unsigned long ideal_runtime, delta_exec;
|
|
|
|
ideal_runtime = sched_slice(cfs_rq, curr);
|
|
delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
|
|
if (delta_exec > ideal_runtime) {
|
|
resched_task(rq_of(cfs_rq)->curr);
|
|
/*
|
|
* The current task ran long enough, ensure it doesn't get
|
|
* re-elected due to buddy favours.
|
|
*/
|
|
clear_buddies(cfs_rq, curr);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Ensure that a task that missed wakeup preemption by a
|
|
* narrow margin doesn't have to wait for a full slice.
|
|
* This also mitigates buddy induced latencies under load.
|
|
*/
|
|
if (!sched_feat(WAKEUP_PREEMPT))
|
|
return;
|
|
|
|
if (delta_exec < sysctl_sched_min_granularity)
|
|
return;
|
|
|
|
if (cfs_rq->nr_running > 1) {
|
|
struct sched_entity *se = __pick_next_entity(cfs_rq);
|
|
s64 delta = curr->vruntime - se->vruntime;
|
|
|
|
if (delta > ideal_runtime)
|
|
resched_task(rq_of(cfs_rq)->curr);
|
|
}
|
|
}
|
|
|
|
static void
|
|
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
/* 'current' is not kept within the tree. */
|
|
if (se->on_rq) {
|
|
/*
|
|
* Any task has to be enqueued before it get to execute on
|
|
* a CPU. So account for the time it spent waiting on the
|
|
* runqueue.
|
|
*/
|
|
update_stats_wait_end(cfs_rq, se);
|
|
__dequeue_entity(cfs_rq, se);
|
|
}
|
|
|
|
update_stats_curr_start(cfs_rq, se);
|
|
cfs_rq->curr = se;
|
|
#ifdef CONFIG_SCHEDSTATS
|
|
/*
|
|
* Track our maximum slice length, if the CPU's load is at
|
|
* least twice that of our own weight (i.e. dont track it
|
|
* when there are only lesser-weight tasks around):
|
|
*/
|
|
if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
|
|
se->slice_max = max(se->slice_max,
|
|
se->sum_exec_runtime - se->prev_sum_exec_runtime);
|
|
}
|
|
#endif
|
|
se->prev_sum_exec_runtime = se->sum_exec_runtime;
|
|
}
|
|
|
|
static int
|
|
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
|
|
|
|
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct sched_entity *se = __pick_next_entity(cfs_rq);
|
|
struct sched_entity *left = se;
|
|
|
|
if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
|
|
se = cfs_rq->next;
|
|
|
|
/*
|
|
* Prefer last buddy, try to return the CPU to a preempted task.
|
|
*/
|
|
if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
|
|
se = cfs_rq->last;
|
|
|
|
clear_buddies(cfs_rq, se);
|
|
|
|
return se;
|
|
}
|
|
|
|
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
|
|
{
|
|
/*
|
|
* If still on the runqueue then deactivate_task()
|
|
* was not called and update_curr() has to be done:
|
|
*/
|
|
if (prev->on_rq)
|
|
update_curr(cfs_rq);
|
|
|
|
check_spread(cfs_rq, prev);
|
|
if (prev->on_rq) {
|
|
update_stats_wait_start(cfs_rq, prev);
|
|
/* Put 'current' back into the tree. */
|
|
__enqueue_entity(cfs_rq, prev);
|
|
}
|
|
cfs_rq->curr = NULL;
|
|
}
|
|
|
|
static void
|
|
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
|
|
{
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
|
|
#ifdef CONFIG_SCHED_HRTICK
|
|
/*
|
|
* queued ticks are scheduled to match the slice, so don't bother
|
|
* validating it and just reschedule.
|
|
*/
|
|
if (queued) {
|
|
resched_task(rq_of(cfs_rq)->curr);
|
|
return;
|
|
}
|
|
/*
|
|
* don't let the period tick interfere with the hrtick preemption
|
|
*/
|
|
if (!sched_feat(DOUBLE_TICK) &&
|
|
hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
|
|
return;
|
|
#endif
|
|
|
|
if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
|
|
check_preempt_tick(cfs_rq, curr);
|
|
}
|
|
|
|
/**************************************************
|
|
* CFS operations on tasks:
|
|
*/
|
|
|
|
#ifdef CONFIG_SCHED_HRTICK
|
|
static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
|
|
WARN_ON(task_rq(p) != rq);
|
|
|
|
if (hrtick_enabled(rq) && cfs_rq->nr_running > 1) {
|
|
u64 slice = sched_slice(cfs_rq, se);
|
|
u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
|
|
s64 delta = slice - ran;
|
|
|
|
if (delta < 0) {
|
|
if (rq->curr == p)
|
|
resched_task(p);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Don't schedule slices shorter than 10000ns, that just
|
|
* doesn't make sense. Rely on vruntime for fairness.
|
|
*/
|
|
if (rq->curr != p)
|
|
delta = max_t(s64, 10000LL, delta);
|
|
|
|
hrtick_start(rq, delta);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* called from enqueue/dequeue and updates the hrtick when the
|
|
* current task is from our class and nr_running is low enough
|
|
* to matter.
|
|
*/
|
|
static void hrtick_update(struct rq *rq)
|
|
{
|
|
struct task_struct *curr = rq->curr;
|
|
|
|
if (curr->sched_class != &fair_sched_class)
|
|
return;
|
|
|
|
if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
|
|
hrtick_start_fair(rq, curr);
|
|
}
|
|
#else /* !CONFIG_SCHED_HRTICK */
|
|
static inline void
|
|
hrtick_start_fair(struct rq *rq, struct task_struct *p)
|
|
{
|
|
}
|
|
|
|
static inline void hrtick_update(struct rq *rq)
|
|
{
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* The enqueue_task method is called before nr_running is
|
|
* increased. Here we update the fair scheduling stats and
|
|
* then put the task into the rbtree:
|
|
*/
|
|
static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se = &p->se;
|
|
int flags = 0;
|
|
|
|
if (wakeup)
|
|
flags |= ENQUEUE_WAKEUP;
|
|
if (p->state == TASK_WAKING)
|
|
flags |= ENQUEUE_MIGRATE;
|
|
|
|
for_each_sched_entity(se) {
|
|
if (se->on_rq)
|
|
break;
|
|
cfs_rq = cfs_rq_of(se);
|
|
enqueue_entity(cfs_rq, se, flags);
|
|
flags = ENQUEUE_WAKEUP;
|
|
}
|
|
|
|
hrtick_update(rq);
|
|
}
|
|
|
|
/*
|
|
* The dequeue_task method is called before nr_running is
|
|
* decreased. We remove the task from the rbtree and
|
|
* update the fair scheduling stats:
|
|
*/
|
|
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se = &p->se;
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
dequeue_entity(cfs_rq, se, sleep);
|
|
/* Don't dequeue parent if it has other entities besides us */
|
|
if (cfs_rq->load.weight)
|
|
break;
|
|
sleep = 1;
|
|
}
|
|
|
|
hrtick_update(rq);
|
|
}
|
|
|
|
/*
|
|
* sched_yield() support is very simple - we dequeue and enqueue.
|
|
*
|
|
* If compat_yield is turned on then we requeue to the end of the tree.
|
|
*/
|
|
static void yield_task_fair(struct rq *rq)
|
|
{
|
|
struct task_struct *curr = rq->curr;
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
|
|
struct sched_entity *rightmost, *se = &curr->se;
|
|
|
|
/*
|
|
* Are we the only task in the tree?
|
|
*/
|
|
if (unlikely(cfs_rq->nr_running == 1))
|
|
return;
|
|
|
|
clear_buddies(cfs_rq, se);
|
|
|
|
if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {
|
|
update_rq_clock(rq);
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
|
|
return;
|
|
}
|
|
/*
|
|
* Find the rightmost entry in the rbtree:
|
|
*/
|
|
rightmost = __pick_last_entity(cfs_rq);
|
|
/*
|
|
* Already in the rightmost position?
|
|
*/
|
|
if (unlikely(!rightmost || entity_before(rightmost, se)))
|
|
return;
|
|
|
|
/*
|
|
* Minimally necessary key value to be last in the tree:
|
|
* Upon rescheduling, sched_class::put_prev_task() will place
|
|
* 'current' within the tree based on its new key value.
|
|
*/
|
|
se->vruntime = rightmost->vruntime + 1;
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
static void task_waking_fair(struct rq *rq, struct task_struct *p)
|
|
{
|
|
struct sched_entity *se = &p->se;
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
|
|
se->vruntime -= cfs_rq->min_vruntime;
|
|
}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
/*
|
|
* effective_load() calculates the load change as seen from the root_task_group
|
|
*
|
|
* Adding load to a group doesn't make a group heavier, but can cause movement
|
|
* of group shares between cpus. Assuming the shares were perfectly aligned one
|
|
* can calculate the shift in shares.
|
|
*
|
|
* The problem is that perfectly aligning the shares is rather expensive, hence
|
|
* we try to avoid doing that too often - see update_shares(), which ratelimits
|
|
* this change.
|
|
*
|
|
* We compensate this by not only taking the current delta into account, but
|
|
* also considering the delta between when the shares were last adjusted and
|
|
* now.
|
|
*
|
|
* We still saw a performance dip, some tracing learned us that between
|
|
* cgroup:/ and cgroup:/foo balancing the number of affine wakeups increased
|
|
* significantly. Therefore try to bias the error in direction of failing
|
|
* the affine wakeup.
|
|
*
|
|
*/
|
|
static long effective_load(struct task_group *tg, int cpu,
|
|
long wl, long wg)
|
|
{
|
|
struct sched_entity *se = tg->se[cpu];
|
|
|
|
if (!tg->parent)
|
|
return wl;
|
|
|
|
/*
|
|
* By not taking the decrease of shares on the other cpu into
|
|
* account our error leans towards reducing the affine wakeups.
|
|
*/
|
|
if (!wl && sched_feat(ASYM_EFF_LOAD))
|
|
return wl;
|
|
|
|
for_each_sched_entity(se) {
|
|
long S, rw, s, a, b;
|
|
long more_w;
|
|
|
|
/*
|
|
* Instead of using this increment, also add the difference
|
|
* between when the shares were last updated and now.
|
|
*/
|
|
more_w = se->my_q->load.weight - se->my_q->rq_weight;
|
|
wl += more_w;
|
|
wg += more_w;
|
|
|
|
S = se->my_q->tg->shares;
|
|
s = se->my_q->shares;
|
|
rw = se->my_q->rq_weight;
|
|
|
|
a = S*(rw + wl);
|
|
b = S*rw + s*wg;
|
|
|
|
wl = s*(a-b);
|
|
|
|
if (likely(b))
|
|
wl /= b;
|
|
|
|
/*
|
|
* Assume the group is already running and will
|
|
* thus already be accounted for in the weight.
|
|
*
|
|
* That is, moving shares between CPUs, does not
|
|
* alter the group weight.
|
|
*/
|
|
wg = 0;
|
|
}
|
|
|
|
return wl;
|
|
}
|
|
|
|
#else
|
|
|
|
static inline unsigned long effective_load(struct task_group *tg, int cpu,
|
|
unsigned long wl, unsigned long wg)
|
|
{
|
|
return wl;
|
|
}
|
|
|
|
#endif
|
|
|
|
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
|
|
{
|
|
struct task_struct *curr = current;
|
|
unsigned long this_load, load;
|
|
int idx, this_cpu, prev_cpu;
|
|
unsigned long tl_per_task;
|
|
unsigned int imbalance;
|
|
struct task_group *tg;
|
|
unsigned long weight;
|
|
int balanced;
|
|
|
|
idx = sd->wake_idx;
|
|
this_cpu = smp_processor_id();
|
|
prev_cpu = task_cpu(p);
|
|
load = source_load(prev_cpu, idx);
|
|
this_load = target_load(this_cpu, idx);
|
|
|
|
if (sync) {
|
|
if (sched_feat(SYNC_LESS) &&
|
|
(curr->se.avg_overlap > sysctl_sched_migration_cost ||
|
|
p->se.avg_overlap > sysctl_sched_migration_cost))
|
|
sync = 0;
|
|
} else {
|
|
if (sched_feat(SYNC_MORE) &&
|
|
(curr->se.avg_overlap < sysctl_sched_migration_cost &&
|
|
p->se.avg_overlap < sysctl_sched_migration_cost))
|
|
sync = 1;
|
|
}
|
|
|
|
/*
|
|
* If sync wakeup then subtract the (maximum possible)
|
|
* effect of the currently running task from the load
|
|
* of the current CPU:
|
|
*/
|
|
if (sync) {
|
|
tg = task_group(current);
|
|
weight = current->se.load.weight;
|
|
|
|
this_load += effective_load(tg, this_cpu, -weight, -weight);
|
|
load += effective_load(tg, prev_cpu, 0, -weight);
|
|
}
|
|
|
|
tg = task_group(p);
|
|
weight = p->se.load.weight;
|
|
|
|
imbalance = 100 + (sd->imbalance_pct - 100) / 2;
|
|
|
|
/*
|
|
* In low-load situations, where prev_cpu is idle and this_cpu is idle
|
|
* due to the sync cause above having dropped this_load to 0, we'll
|
|
* always have an imbalance, but there's really nothing you can do
|
|
* about that, so that's good too.
|
|
*
|
|
* Otherwise check if either cpus are near enough in load to allow this
|
|
* task to be woken on this_cpu.
|
|
*/
|
|
balanced = !this_load ||
|
|
100*(this_load + effective_load(tg, this_cpu, weight, weight)) <=
|
|
imbalance*(load + effective_load(tg, prev_cpu, 0, weight));
|
|
|
|
/*
|
|
* If the currently running task will sleep within
|
|
* a reasonable amount of time then attract this newly
|
|
* woken task:
|
|
*/
|
|
if (sync && balanced)
|
|
return 1;
|
|
|
|
schedstat_inc(p, se.nr_wakeups_affine_attempts);
|
|
tl_per_task = cpu_avg_load_per_task(this_cpu);
|
|
|
|
if (balanced ||
|
|
(this_load <= load &&
|
|
this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
|
|
/*
|
|
* This domain has SD_WAKE_AFFINE and
|
|
* p is cache cold in this domain, and
|
|
* there is no bad imbalance.
|
|
*/
|
|
schedstat_inc(sd, ttwu_move_affine);
|
|
schedstat_inc(p, se.nr_wakeups_affine);
|
|
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* find_idlest_group finds and returns the least busy CPU group within the
|
|
* domain.
|
|
*/
|
|
static struct sched_group *
|
|
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
|
|
int this_cpu, int load_idx)
|
|
{
|
|
struct sched_group *idlest = NULL, *this = NULL, *group = sd->groups;
|
|
unsigned long min_load = ULONG_MAX, this_load = 0;
|
|
int imbalance = 100 + (sd->imbalance_pct-100)/2;
|
|
|
|
do {
|
|
unsigned long load, avg_load;
|
|
int local_group;
|
|
int i;
|
|
|
|
/* Skip over this group if it has no CPUs allowed */
|
|
if (!cpumask_intersects(sched_group_cpus(group),
|
|
&p->cpus_allowed))
|
|
continue;
|
|
|
|
local_group = cpumask_test_cpu(this_cpu,
|
|
sched_group_cpus(group));
|
|
|
|
/* Tally up the load of all CPUs in the group */
|
|
avg_load = 0;
|
|
|
|
for_each_cpu(i, sched_group_cpus(group)) {
|
|
/* Bias balancing toward cpus of our domain */
|
|
if (local_group)
|
|
load = source_load(i, load_idx);
|
|
else
|
|
load = target_load(i, load_idx);
|
|
|
|
avg_load += load;
|
|
}
|
|
|
|
/* Adjust by relative CPU power of the group */
|
|
avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;
|
|
|
|
if (local_group) {
|
|
this_load = avg_load;
|
|
this = group;
|
|
} else if (avg_load < min_load) {
|
|
min_load = avg_load;
|
|
idlest = group;
|
|
}
|
|
} while (group = group->next, group != sd->groups);
|
|
|
|
if (!idlest || 100*this_load < imbalance*min_load)
|
|
return NULL;
|
|
return idlest;
|
|
}
|
|
|
|
/*
|
|
* find_idlest_cpu - find the idlest cpu among the cpus in group.
|
|
*/
|
|
static int
|
|
find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
|
|
{
|
|
unsigned long load, min_load = ULONG_MAX;
|
|
int idlest = -1;
|
|
int i;
|
|
|
|
/* Traverse only the allowed CPUs */
|
|
for_each_cpu_and(i, sched_group_cpus(group), &p->cpus_allowed) {
|
|
load = weighted_cpuload(i);
|
|
|
|
if (load < min_load || (load == min_load && i == this_cpu)) {
|
|
min_load = load;
|
|
idlest = i;
|
|
}
|
|
}
|
|
|
|
return idlest;
|
|
}
|
|
|
|
/*
|
|
* Try and locate an idle CPU in the sched_domain.
|
|
*/
|
|
static int
|
|
select_idle_sibling(struct task_struct *p, struct sched_domain *sd, int target)
|
|
{
|
|
int cpu = smp_processor_id();
|
|
int prev_cpu = task_cpu(p);
|
|
int i;
|
|
|
|
/*
|
|
* If this domain spans both cpu and prev_cpu (see the SD_WAKE_AFFINE
|
|
* test in select_task_rq_fair) and the prev_cpu is idle then that's
|
|
* always a better target than the current cpu.
|
|
*/
|
|
if (target == cpu && !cpu_rq(prev_cpu)->cfs.nr_running)
|
|
return prev_cpu;
|
|
|
|
/*
|
|
* Otherwise, iterate the domain and find an elegible idle cpu.
|
|
*/
|
|
for_each_cpu_and(i, sched_domain_span(sd), &p->cpus_allowed) {
|
|
if (!cpu_rq(i)->cfs.nr_running) {
|
|
target = i;
|
|
break;
|
|
}
|
|
}
|
|
|
|
return target;
|
|
}
|
|
|
|
/*
|
|
* sched_balance_self: balance the current task (running on cpu) in domains
|
|
* that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
|
|
* SD_BALANCE_EXEC.
|
|
*
|
|
* Balance, ie. select the least loaded group.
|
|
*
|
|
* Returns the target CPU number, or the same CPU if no balancing is needed.
|
|
*
|
|
* preempt must be disabled.
|
|
*/
|
|
static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
|
|
{
|
|
struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
|
|
int cpu = smp_processor_id();
|
|
int prev_cpu = task_cpu(p);
|
|
int new_cpu = cpu;
|
|
int want_affine = 0;
|
|
int want_sd = 1;
|
|
int sync = wake_flags & WF_SYNC;
|
|
|
|
if (sd_flag & SD_BALANCE_WAKE) {
|
|
if (sched_feat(AFFINE_WAKEUPS) &&
|
|
cpumask_test_cpu(cpu, &p->cpus_allowed))
|
|
want_affine = 1;
|
|
new_cpu = prev_cpu;
|
|
}
|
|
|
|
for_each_domain(cpu, tmp) {
|
|
if (!(tmp->flags & SD_LOAD_BALANCE))
|
|
continue;
|
|
|
|
/*
|
|
* If power savings logic is enabled for a domain, see if we
|
|
* are not overloaded, if so, don't balance wider.
|
|
*/
|
|
if (tmp->flags & (SD_POWERSAVINGS_BALANCE|SD_PREFER_LOCAL)) {
|
|
unsigned long power = 0;
|
|
unsigned long nr_running = 0;
|
|
unsigned long capacity;
|
|
int i;
|
|
|
|
for_each_cpu(i, sched_domain_span(tmp)) {
|
|
power += power_of(i);
|
|
nr_running += cpu_rq(i)->cfs.nr_running;
|
|
}
|
|
|
|
capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
|
|
|
|
if (tmp->flags & SD_POWERSAVINGS_BALANCE)
|
|
nr_running /= 2;
|
|
|
|
if (nr_running < capacity)
|
|
want_sd = 0;
|
|
}
|
|
|
|
/*
|
|
* While iterating the domains looking for a spanning
|
|
* WAKE_AFFINE domain, adjust the affine target to any idle cpu
|
|
* in cache sharing domains along the way.
|
|
*/
|
|
if (want_affine) {
|
|
int target = -1;
|
|
|
|
/*
|
|
* If both cpu and prev_cpu are part of this domain,
|
|
* cpu is a valid SD_WAKE_AFFINE target.
|
|
*/
|
|
if (cpumask_test_cpu(prev_cpu, sched_domain_span(tmp)))
|
|
target = cpu;
|
|
|
|
/*
|
|
* If there's an idle sibling in this domain, make that
|
|
* the wake_affine target instead of the current cpu.
|
|
*/
|
|
if (tmp->flags & SD_PREFER_SIBLING)
|
|
target = select_idle_sibling(p, tmp, target);
|
|
|
|
if (target >= 0) {
|
|
if (tmp->flags & SD_WAKE_AFFINE) {
|
|
affine_sd = tmp;
|
|
want_affine = 0;
|
|
}
|
|
cpu = target;
|
|
}
|
|
}
|
|
|
|
if (!want_sd && !want_affine)
|
|
break;
|
|
|
|
if (!(tmp->flags & sd_flag))
|
|
continue;
|
|
|
|
if (want_sd)
|
|
sd = tmp;
|
|
}
|
|
|
|
if (sched_feat(LB_SHARES_UPDATE)) {
|
|
/*
|
|
* Pick the largest domain to update shares over
|
|
*/
|
|
tmp = sd;
|
|
if (affine_sd && (!tmp ||
|
|
cpumask_weight(sched_domain_span(affine_sd)) >
|
|
cpumask_weight(sched_domain_span(sd))))
|
|
tmp = affine_sd;
|
|
|
|
if (tmp)
|
|
update_shares(tmp);
|
|
}
|
|
|
|
if (affine_sd && wake_affine(affine_sd, p, sync))
|
|
return cpu;
|
|
|
|
while (sd) {
|
|
int load_idx = sd->forkexec_idx;
|
|
struct sched_group *group;
|
|
int weight;
|
|
|
|
if (!(sd->flags & sd_flag)) {
|
|
sd = sd->child;
|
|
continue;
|
|
}
|
|
|
|
if (sd_flag & SD_BALANCE_WAKE)
|
|
load_idx = sd->wake_idx;
|
|
|
|
group = find_idlest_group(sd, p, cpu, load_idx);
|
|
if (!group) {
|
|
sd = sd->child;
|
|
continue;
|
|
}
|
|
|
|
new_cpu = find_idlest_cpu(group, p, cpu);
|
|
if (new_cpu == -1 || new_cpu == cpu) {
|
|
/* Now try balancing at a lower domain level of cpu */
|
|
sd = sd->child;
|
|
continue;
|
|
}
|
|
|
|
/* Now try balancing at a lower domain level of new_cpu */
|
|
cpu = new_cpu;
|
|
weight = cpumask_weight(sched_domain_span(sd));
|
|
sd = NULL;
|
|
for_each_domain(cpu, tmp) {
|
|
if (weight <= cpumask_weight(sched_domain_span(tmp)))
|
|
break;
|
|
if (tmp->flags & sd_flag)
|
|
sd = tmp;
|
|
}
|
|
/* while loop will break here if sd == NULL */
|
|
}
|
|
|
|
return new_cpu;
|
|
}
|
|
#endif /* CONFIG_SMP */
|
|
|
|
/*
|
|
* Adaptive granularity
|
|
*
|
|
* se->avg_wakeup gives the average time a task runs until it does a wakeup,
|
|
* with the limit of wakeup_gran -- when it never does a wakeup.
|
|
*
|
|
* So the smaller avg_wakeup is the faster we want this task to preempt,
|
|
* but we don't want to treat the preemptee unfairly and therefore allow it
|
|
* to run for at least the amount of time we'd like to run.
|
|
*
|
|
* NOTE: we use 2*avg_wakeup to increase the probability of actually doing one
|
|
*
|
|
* NOTE: we use *nr_running to scale with load, this nicely matches the
|
|
* degrading latency on load.
|
|
*/
|
|
static unsigned long
|
|
adaptive_gran(struct sched_entity *curr, struct sched_entity *se)
|
|
{
|
|
u64 this_run = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
|
|
u64 expected_wakeup = 2*se->avg_wakeup * cfs_rq_of(se)->nr_running;
|
|
u64 gran = 0;
|
|
|
|
if (this_run < expected_wakeup)
|
|
gran = expected_wakeup - this_run;
|
|
|
|
return min_t(s64, gran, sysctl_sched_wakeup_granularity);
|
|
}
|
|
|
|
static unsigned long
|
|
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
|
|
{
|
|
unsigned long gran = sysctl_sched_wakeup_granularity;
|
|
|
|
if (cfs_rq_of(curr)->curr && sched_feat(ADAPTIVE_GRAN))
|
|
gran = adaptive_gran(curr, se);
|
|
|
|
/*
|
|
* Since its curr running now, convert the gran from real-time
|
|
* to virtual-time in his units.
|
|
*/
|
|
if (sched_feat(ASYM_GRAN)) {
|
|
/*
|
|
* By using 'se' instead of 'curr' we penalize light tasks, so
|
|
* they get preempted easier. That is, if 'se' < 'curr' then
|
|
* the resulting gran will be larger, therefore penalizing the
|
|
* lighter, if otoh 'se' > 'curr' then the resulting gran will
|
|
* be smaller, again penalizing the lighter task.
|
|
*
|
|
* This is especially important for buddies when the leftmost
|
|
* task is higher priority than the buddy.
|
|
*/
|
|
if (unlikely(se->load.weight != NICE_0_LOAD))
|
|
gran = calc_delta_fair(gran, se);
|
|
} else {
|
|
if (unlikely(curr->load.weight != NICE_0_LOAD))
|
|
gran = calc_delta_fair(gran, curr);
|
|
}
|
|
|
|
return gran;
|
|
}
|
|
|
|
/*
|
|
* Should 'se' preempt 'curr'.
|
|
*
|
|
* |s1
|
|
* |s2
|
|
* |s3
|
|
* g
|
|
* |<--->|c
|
|
*
|
|
* w(c, s1) = -1
|
|
* w(c, s2) = 0
|
|
* w(c, s3) = 1
|
|
*
|
|
*/
|
|
static int
|
|
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
|
|
{
|
|
s64 gran, vdiff = curr->vruntime - se->vruntime;
|
|
|
|
if (vdiff <= 0)
|
|
return -1;
|
|
|
|
gran = wakeup_gran(curr, se);
|
|
if (vdiff > gran)
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void set_last_buddy(struct sched_entity *se)
|
|
{
|
|
if (likely(task_of(se)->policy != SCHED_IDLE)) {
|
|
for_each_sched_entity(se)
|
|
cfs_rq_of(se)->last = se;
|
|
}
|
|
}
|
|
|
|
static void set_next_buddy(struct sched_entity *se)
|
|
{
|
|
if (likely(task_of(se)->policy != SCHED_IDLE)) {
|
|
for_each_sched_entity(se)
|
|
cfs_rq_of(se)->next = se;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Preempt the current task with a newly woken task if needed:
|
|
*/
|
|
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
|
|
{
|
|
struct task_struct *curr = rq->curr;
|
|
struct sched_entity *se = &curr->se, *pse = &p->se;
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
|
|
int sync = wake_flags & WF_SYNC;
|
|
int scale = cfs_rq->nr_running >= sched_nr_latency;
|
|
|
|
if (unlikely(rt_prio(p->prio)))
|
|
goto preempt;
|
|
|
|
if (unlikely(p->sched_class != &fair_sched_class))
|
|
return;
|
|
|
|
if (unlikely(se == pse))
|
|
return;
|
|
|
|
if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK))
|
|
set_next_buddy(pse);
|
|
|
|
/*
|
|
* We can come here with TIF_NEED_RESCHED already set from new task
|
|
* wake up path.
|
|
*/
|
|
if (test_tsk_need_resched(curr))
|
|
return;
|
|
|
|
/*
|
|
* Batch and idle tasks do not preempt (their preemption is driven by
|
|
* the tick):
|
|
*/
|
|
if (unlikely(p->policy != SCHED_NORMAL))
|
|
return;
|
|
|
|
/* Idle tasks are by definition preempted by everybody. */
|
|
if (unlikely(curr->policy == SCHED_IDLE))
|
|
goto preempt;
|
|
|
|
if (sched_feat(WAKEUP_SYNC) && sync)
|
|
goto preempt;
|
|
|
|
if (sched_feat(WAKEUP_OVERLAP) &&
|
|
se->avg_overlap < sysctl_sched_migration_cost &&
|
|
pse->avg_overlap < sysctl_sched_migration_cost)
|
|
goto preempt;
|
|
|
|
if (!sched_feat(WAKEUP_PREEMPT))
|
|
return;
|
|
|
|
update_curr(cfs_rq);
|
|
find_matching_se(&se, &pse);
|
|
BUG_ON(!pse);
|
|
if (wakeup_preempt_entity(se, pse) == 1)
|
|
goto preempt;
|
|
|
|
return;
|
|
|
|
preempt:
|
|
resched_task(curr);
|
|
/*
|
|
* Only set the backward buddy when the current task is still
|
|
* on the rq. This can happen when a wakeup gets interleaved
|
|
* with schedule on the ->pre_schedule() or idle_balance()
|
|
* point, either of which can * drop the rq lock.
|
|
*
|
|
* Also, during early boot the idle thread is in the fair class,
|
|
* for obvious reasons its a bad idea to schedule back to it.
|
|
*/
|
|
if (unlikely(!se->on_rq || curr == rq->idle))
|
|
return;
|
|
|
|
if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
|
|
set_last_buddy(se);
|
|
}
|
|
|
|
static struct task_struct *pick_next_task_fair(struct rq *rq)
|
|
{
|
|
struct task_struct *p;
|
|
struct cfs_rq *cfs_rq = &rq->cfs;
|
|
struct sched_entity *se;
|
|
|
|
if (!cfs_rq->nr_running)
|
|
return NULL;
|
|
|
|
do {
|
|
se = pick_next_entity(cfs_rq);
|
|
set_next_entity(cfs_rq, se);
|
|
cfs_rq = group_cfs_rq(se);
|
|
} while (cfs_rq);
|
|
|
|
p = task_of(se);
|
|
hrtick_start_fair(rq, p);
|
|
|
|
return p;
|
|
}
|
|
|
|
/*
|
|
* Account for a descheduled task:
|
|
*/
|
|
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
|
|
{
|
|
struct sched_entity *se = &prev->se;
|
|
struct cfs_rq *cfs_rq;
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
put_prev_entity(cfs_rq, se);
|
|
}
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
/**************************************************
|
|
* Fair scheduling class load-balancing methods:
|
|
*/
|
|
|
|
/*
|
|
* pull_task - move a task from a remote runqueue to the local runqueue.
|
|
* Both runqueues must be locked.
|
|
*/
|
|
static void pull_task(struct rq *src_rq, struct task_struct *p,
|
|
struct rq *this_rq, int this_cpu)
|
|
{
|
|
deactivate_task(src_rq, p, 0);
|
|
set_task_cpu(p, this_cpu);
|
|
activate_task(this_rq, p, 0);
|
|
check_preempt_curr(this_rq, p, 0);
|
|
}
|
|
|
|
/*
|
|
* can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
|
|
*/
|
|
static
|
|
int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
|
|
struct sched_domain *sd, enum cpu_idle_type idle,
|
|
int *all_pinned)
|
|
{
|
|
int tsk_cache_hot = 0;
|
|
/*
|
|
* We do not migrate tasks that are:
|
|
* 1) running (obviously), or
|
|
* 2) cannot be migrated to this CPU due to cpus_allowed, or
|
|
* 3) are cache-hot on their current CPU.
|
|
*/
|
|
if (!cpumask_test_cpu(this_cpu, &p->cpus_allowed)) {
|
|
schedstat_inc(p, se.nr_failed_migrations_affine);
|
|
return 0;
|
|
}
|
|
*all_pinned = 0;
|
|
|
|
if (task_running(rq, p)) {
|
|
schedstat_inc(p, se.nr_failed_migrations_running);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Aggressive migration if:
|
|
* 1) task is cache cold, or
|
|
* 2) too many balance attempts have failed.
|
|
*/
|
|
|
|
tsk_cache_hot = task_hot(p, rq->clock, sd);
|
|
if (!tsk_cache_hot ||
|
|
sd->nr_balance_failed > sd->cache_nice_tries) {
|
|
#ifdef CONFIG_SCHEDSTATS
|
|
if (tsk_cache_hot) {
|
|
schedstat_inc(sd, lb_hot_gained[idle]);
|
|
schedstat_inc(p, se.nr_forced_migrations);
|
|
}
|
|
#endif
|
|
return 1;
|
|
}
|
|
|
|
if (tsk_cache_hot) {
|
|
schedstat_inc(p, se.nr_failed_migrations_hot);
|
|
return 0;
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* move_one_task tries to move exactly one task from busiest to this_rq, as
|
|
* part of active balancing operations within "domain".
|
|
* Returns 1 if successful and 0 otherwise.
|
|
*
|
|
* Called with both runqueues locked.
|
|
*/
|
|
static int
|
|
move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
|
struct sched_domain *sd, enum cpu_idle_type idle)
|
|
{
|
|
struct task_struct *p, *n;
|
|
struct cfs_rq *cfs_rq;
|
|
int pinned = 0;
|
|
|
|
for_each_leaf_cfs_rq(busiest, cfs_rq) {
|
|
list_for_each_entry_safe(p, n, &cfs_rq->tasks, se.group_node) {
|
|
|
|
if (!can_migrate_task(p, busiest, this_cpu,
|
|
sd, idle, &pinned))
|
|
continue;
|
|
|
|
pull_task(busiest, p, this_rq, this_cpu);
|
|
/*
|
|
* Right now, this is only the second place pull_task()
|
|
* is called, so we can safely collect pull_task()
|
|
* stats here rather than inside pull_task().
|
|
*/
|
|
schedstat_inc(sd, lb_gained[idle]);
|
|
return 1;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static unsigned long
|
|
balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
|
unsigned long max_load_move, struct sched_domain *sd,
|
|
enum cpu_idle_type idle, int *all_pinned,
|
|
int *this_best_prio, struct cfs_rq *busiest_cfs_rq)
|
|
{
|
|
int loops = 0, pulled = 0, pinned = 0;
|
|
long rem_load_move = max_load_move;
|
|
struct task_struct *p, *n;
|
|
|
|
if (max_load_move == 0)
|
|
goto out;
|
|
|
|
pinned = 1;
|
|
|
|
list_for_each_entry_safe(p, n, &busiest_cfs_rq->tasks, se.group_node) {
|
|
if (loops++ > sysctl_sched_nr_migrate)
|
|
break;
|
|
|
|
if ((p->se.load.weight >> 1) > rem_load_move ||
|
|
!can_migrate_task(p, busiest, this_cpu, sd, idle, &pinned))
|
|
continue;
|
|
|
|
pull_task(busiest, p, this_rq, this_cpu);
|
|
pulled++;
|
|
rem_load_move -= p->se.load.weight;
|
|
|
|
#ifdef CONFIG_PREEMPT
|
|
/*
|
|
* NEWIDLE balancing is a source of latency, so preemptible
|
|
* kernels will stop after the first task is pulled to minimize
|
|
* the critical section.
|
|
*/
|
|
if (idle == CPU_NEWLY_IDLE)
|
|
break;
|
|
#endif
|
|
|
|
/*
|
|
* We only want to steal up to the prescribed amount of
|
|
* weighted load.
|
|
*/
|
|
if (rem_load_move <= 0)
|
|
break;
|
|
|
|
if (p->prio < *this_best_prio)
|
|
*this_best_prio = p->prio;
|
|
}
|
|
out:
|
|
/*
|
|
* Right now, this is one of only two places pull_task() is called,
|
|
* so we can safely collect pull_task() stats here rather than
|
|
* inside pull_task().
|
|
*/
|
|
schedstat_add(sd, lb_gained[idle], pulled);
|
|
|
|
if (all_pinned)
|
|
*all_pinned = pinned;
|
|
|
|
return max_load_move - rem_load_move;
|
|
}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
static unsigned long
|
|
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
|
unsigned long max_load_move,
|
|
struct sched_domain *sd, enum cpu_idle_type idle,
|
|
int *all_pinned, int *this_best_prio)
|
|
{
|
|
long rem_load_move = max_load_move;
|
|
int busiest_cpu = cpu_of(busiest);
|
|
struct task_group *tg;
|
|
|
|
rcu_read_lock();
|
|
update_h_load(busiest_cpu);
|
|
|
|
list_for_each_entry_rcu(tg, &task_groups, list) {
|
|
struct cfs_rq *busiest_cfs_rq = tg->cfs_rq[busiest_cpu];
|
|
unsigned long busiest_h_load = busiest_cfs_rq->h_load;
|
|
unsigned long busiest_weight = busiest_cfs_rq->load.weight;
|
|
u64 rem_load, moved_load;
|
|
|
|
/*
|
|
* empty group
|
|
*/
|
|
if (!busiest_cfs_rq->task_weight)
|
|
continue;
|
|
|
|
rem_load = (u64)rem_load_move * busiest_weight;
|
|
rem_load = div_u64(rem_load, busiest_h_load + 1);
|
|
|
|
moved_load = balance_tasks(this_rq, this_cpu, busiest,
|
|
rem_load, sd, idle, all_pinned, this_best_prio,
|
|
busiest_cfs_rq);
|
|
|
|
if (!moved_load)
|
|
continue;
|
|
|
|
moved_load *= busiest_h_load;
|
|
moved_load = div_u64(moved_load, busiest_weight + 1);
|
|
|
|
rem_load_move -= moved_load;
|
|
if (rem_load_move < 0)
|
|
break;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return max_load_move - rem_load_move;
|
|
}
|
|
#else
|
|
static unsigned long
|
|
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
|
unsigned long max_load_move,
|
|
struct sched_domain *sd, enum cpu_idle_type idle,
|
|
int *all_pinned, int *this_best_prio)
|
|
{
|
|
return balance_tasks(this_rq, this_cpu, busiest,
|
|
max_load_move, sd, idle, all_pinned,
|
|
this_best_prio, &busiest->cfs);
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* move_tasks tries to move up to max_load_move weighted load from busiest to
|
|
* this_rq, as part of a balancing operation within domain "sd".
|
|
* Returns 1 if successful and 0 otherwise.
|
|
*
|
|
* Called with both runqueues locked.
|
|
*/
|
|
static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
|
unsigned long max_load_move,
|
|
struct sched_domain *sd, enum cpu_idle_type idle,
|
|
int *all_pinned)
|
|
{
|
|
unsigned long total_load_moved = 0, load_moved;
|
|
int this_best_prio = this_rq->curr->prio;
|
|
|
|
do {
|
|
load_moved = load_balance_fair(this_rq, this_cpu, busiest,
|
|
max_load_move - total_load_moved,
|
|
sd, idle, all_pinned, &this_best_prio);
|
|
|
|
total_load_moved += load_moved;
|
|
|
|
#ifdef CONFIG_PREEMPT
|
|
/*
|
|
* NEWIDLE balancing is a source of latency, so preemptible
|
|
* kernels will stop after the first task is pulled to minimize
|
|
* the critical section.
|
|
*/
|
|
if (idle == CPU_NEWLY_IDLE && this_rq->nr_running)
|
|
break;
|
|
|
|
if (raw_spin_is_contended(&this_rq->lock) ||
|
|
raw_spin_is_contended(&busiest->lock))
|
|
break;
|
|
#endif
|
|
} while (load_moved && max_load_move > total_load_moved);
|
|
|
|
return total_load_moved > 0;
|
|
}
|
|
|
|
/********** Helpers for find_busiest_group ************************/
|
|
/*
|
|
* sd_lb_stats - Structure to store the statistics of a sched_domain
|
|
* during load balancing.
|
|
*/
|
|
struct sd_lb_stats {
|
|
struct sched_group *busiest; /* Busiest group in this sd */
|
|
struct sched_group *this; /* Local group in this sd */
|
|
unsigned long total_load; /* Total load of all groups in sd */
|
|
unsigned long total_pwr; /* Total power of all groups in sd */
|
|
unsigned long avg_load; /* Average load across all groups in sd */
|
|
|
|
/** Statistics of this group */
|
|
unsigned long this_load;
|
|
unsigned long this_load_per_task;
|
|
unsigned long this_nr_running;
|
|
|
|
/* Statistics of the busiest group */
|
|
unsigned long max_load;
|
|
unsigned long busiest_load_per_task;
|
|
unsigned long busiest_nr_running;
|
|
|
|
int group_imb; /* Is there imbalance in this sd */
|
|
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
|
|
int power_savings_balance; /* Is powersave balance needed for this sd */
|
|
struct sched_group *group_min; /* Least loaded group in sd */
|
|
struct sched_group *group_leader; /* Group which relieves group_min */
|
|
unsigned long min_load_per_task; /* load_per_task in group_min */
|
|
unsigned long leader_nr_running; /* Nr running of group_leader */
|
|
unsigned long min_nr_running; /* Nr running of group_min */
|
|
#endif
|
|
};
|
|
|
|
/*
|
|
* sg_lb_stats - stats of a sched_group required for load_balancing
|
|
*/
|
|
struct sg_lb_stats {
|
|
unsigned long avg_load; /*Avg load across the CPUs of the group */
|
|
unsigned long group_load; /* Total load over the CPUs of the group */
|
|
unsigned long sum_nr_running; /* Nr tasks running in the group */
|
|
unsigned long sum_weighted_load; /* Weighted load of group's tasks */
|
|
unsigned long group_capacity;
|
|
int group_imb; /* Is there an imbalance in the group ? */
|
|
};
|
|
|
|
/**
|
|
* group_first_cpu - Returns the first cpu in the cpumask of a sched_group.
|
|
* @group: The group whose first cpu is to be returned.
|
|
*/
|
|
static inline unsigned int group_first_cpu(struct sched_group *group)
|
|
{
|
|
return cpumask_first(sched_group_cpus(group));
|
|
}
|
|
|
|
/**
|
|
* get_sd_load_idx - Obtain the load index for a given sched domain.
|
|
* @sd: The sched_domain whose load_idx is to be obtained.
|
|
* @idle: The Idle status of the CPU for whose sd load_icx is obtained.
|
|
*/
|
|
static inline int get_sd_load_idx(struct sched_domain *sd,
|
|
enum cpu_idle_type idle)
|
|
{
|
|
int load_idx;
|
|
|
|
switch (idle) {
|
|
case CPU_NOT_IDLE:
|
|
load_idx = sd->busy_idx;
|
|
break;
|
|
|
|
case CPU_NEWLY_IDLE:
|
|
load_idx = sd->newidle_idx;
|
|
break;
|
|
default:
|
|
load_idx = sd->idle_idx;
|
|
break;
|
|
}
|
|
|
|
return load_idx;
|
|
}
|
|
|
|
|
|
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
|
|
/**
|
|
* init_sd_power_savings_stats - Initialize power savings statistics for
|
|
* the given sched_domain, during load balancing.
|
|
*
|
|
* @sd: Sched domain whose power-savings statistics are to be initialized.
|
|
* @sds: Variable containing the statistics for sd.
|
|
* @idle: Idle status of the CPU at which we're performing load-balancing.
|
|
*/
|
|
static inline void init_sd_power_savings_stats(struct sched_domain *sd,
|
|
struct sd_lb_stats *sds, enum cpu_idle_type idle)
|
|
{
|
|
/*
|
|
* Busy processors will not participate in power savings
|
|
* balance.
|
|
*/
|
|
if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
|
|
sds->power_savings_balance = 0;
|
|
else {
|
|
sds->power_savings_balance = 1;
|
|
sds->min_nr_running = ULONG_MAX;
|
|
sds->leader_nr_running = 0;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* update_sd_power_savings_stats - Update the power saving stats for a
|
|
* sched_domain while performing load balancing.
|
|
*
|
|
* @group: sched_group belonging to the sched_domain under consideration.
|
|
* @sds: Variable containing the statistics of the sched_domain
|
|
* @local_group: Does group contain the CPU for which we're performing
|
|
* load balancing ?
|
|
* @sgs: Variable containing the statistics of the group.
|
|
*/
|
|
static inline void update_sd_power_savings_stats(struct sched_group *group,
|
|
struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
|
|
{
|
|
|
|
if (!sds->power_savings_balance)
|
|
return;
|
|
|
|
/*
|
|
* If the local group is idle or completely loaded
|
|
* no need to do power savings balance at this domain
|
|
*/
|
|
if (local_group && (sds->this_nr_running >= sgs->group_capacity ||
|
|
!sds->this_nr_running))
|
|
sds->power_savings_balance = 0;
|
|
|
|
/*
|
|
* If a group is already running at full capacity or idle,
|
|
* don't include that group in power savings calculations
|
|
*/
|
|
if (!sds->power_savings_balance ||
|
|
sgs->sum_nr_running >= sgs->group_capacity ||
|
|
!sgs->sum_nr_running)
|
|
return;
|
|
|
|
/*
|
|
* Calculate the group which has the least non-idle load.
|
|
* This is the group from where we need to pick up the load
|
|
* for saving power
|
|
*/
|
|
if ((sgs->sum_nr_running < sds->min_nr_running) ||
|
|
(sgs->sum_nr_running == sds->min_nr_running &&
|
|
group_first_cpu(group) > group_first_cpu(sds->group_min))) {
|
|
sds->group_min = group;
|
|
sds->min_nr_running = sgs->sum_nr_running;
|
|
sds->min_load_per_task = sgs->sum_weighted_load /
|
|
sgs->sum_nr_running;
|
|
}
|
|
|
|
/*
|
|
* Calculate the group which is almost near its
|
|
* capacity but still has some space to pick up some load
|
|
* from other group and save more power
|
|
*/
|
|
if (sgs->sum_nr_running + 1 > sgs->group_capacity)
|
|
return;
|
|
|
|
if (sgs->sum_nr_running > sds->leader_nr_running ||
|
|
(sgs->sum_nr_running == sds->leader_nr_running &&
|
|
group_first_cpu(group) < group_first_cpu(sds->group_leader))) {
|
|
sds->group_leader = group;
|
|
sds->leader_nr_running = sgs->sum_nr_running;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* check_power_save_busiest_group - see if there is potential for some power-savings balance
|
|
* @sds: Variable containing the statistics of the sched_domain
|
|
* under consideration.
|
|
* @this_cpu: Cpu at which we're currently performing load-balancing.
|
|
* @imbalance: Variable to store the imbalance.
|
|
*
|
|
* Description:
|
|
* Check if we have potential to perform some power-savings balance.
|
|
* If yes, set the busiest group to be the least loaded group in the
|
|
* sched_domain, so that it's CPUs can be put to idle.
|
|
*
|
|
* Returns 1 if there is potential to perform power-savings balance.
|
|
* Else returns 0.
|
|
*/
|
|
static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
|
|
int this_cpu, unsigned long *imbalance)
|
|
{
|
|
if (!sds->power_savings_balance)
|
|
return 0;
|
|
|
|
if (sds->this != sds->group_leader ||
|
|
sds->group_leader == sds->group_min)
|
|
return 0;
|
|
|
|
*imbalance = sds->min_load_per_task;
|
|
sds->busiest = sds->group_min;
|
|
|
|
return 1;
|
|
|
|
}
|
|
#else /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
|
|
static inline void init_sd_power_savings_stats(struct sched_domain *sd,
|
|
struct sd_lb_stats *sds, enum cpu_idle_type idle)
|
|
{
|
|
return;
|
|
}
|
|
|
|
static inline void update_sd_power_savings_stats(struct sched_group *group,
|
|
struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
|
|
{
|
|
return;
|
|
}
|
|
|
|
static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
|
|
int this_cpu, unsigned long *imbalance)
|
|
{
|
|
return 0;
|
|
}
|
|
#endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
|
|
|
|
|
|
unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
|
|
{
|
|
return SCHED_LOAD_SCALE;
|
|
}
|
|
|
|
unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu)
|
|
{
|
|
return default_scale_freq_power(sd, cpu);
|
|
}
|
|
|
|
unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
|
|
{
|
|
unsigned long weight = cpumask_weight(sched_domain_span(sd));
|
|
unsigned long smt_gain = sd->smt_gain;
|
|
|
|
smt_gain /= weight;
|
|
|
|
return smt_gain;
|
|
}
|
|
|
|
unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
|
|
{
|
|
return default_scale_smt_power(sd, cpu);
|
|
}
|
|
|
|
unsigned long scale_rt_power(int cpu)
|
|
{
|
|
struct rq *rq = cpu_rq(cpu);
|
|
u64 total, available;
|
|
|
|
sched_avg_update(rq);
|
|
|
|
total = sched_avg_period() + (rq->clock - rq->age_stamp);
|
|
available = total - rq->rt_avg;
|
|
|
|
if (unlikely((s64)total < SCHED_LOAD_SCALE))
|
|
total = SCHED_LOAD_SCALE;
|
|
|
|
total >>= SCHED_LOAD_SHIFT;
|
|
|
|
return div_u64(available, total);
|
|
}
|
|
|
|
static void update_cpu_power(struct sched_domain *sd, int cpu)
|
|
{
|
|
unsigned long weight = cpumask_weight(sched_domain_span(sd));
|
|
unsigned long power = SCHED_LOAD_SCALE;
|
|
struct sched_group *sdg = sd->groups;
|
|
|
|
if (sched_feat(ARCH_POWER))
|
|
power *= arch_scale_freq_power(sd, cpu);
|
|
else
|
|
power *= default_scale_freq_power(sd, cpu);
|
|
|
|
power >>= SCHED_LOAD_SHIFT;
|
|
|
|
if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
|
|
if (sched_feat(ARCH_POWER))
|
|
power *= arch_scale_smt_power(sd, cpu);
|
|
else
|
|
power *= default_scale_smt_power(sd, cpu);
|
|
|
|
power >>= SCHED_LOAD_SHIFT;
|
|
}
|
|
|
|
power *= scale_rt_power(cpu);
|
|
power >>= SCHED_LOAD_SHIFT;
|
|
|
|
if (!power)
|
|
power = 1;
|
|
|
|
sdg->cpu_power = power;
|
|
}
|
|
|
|
static void update_group_power(struct sched_domain *sd, int cpu)
|
|
{
|
|
struct sched_domain *child = sd->child;
|
|
struct sched_group *group, *sdg = sd->groups;
|
|
unsigned long power;
|
|
|
|
if (!child) {
|
|
update_cpu_power(sd, cpu);
|
|
return;
|
|
}
|
|
|
|
power = 0;
|
|
|
|
group = child->groups;
|
|
do {
|
|
power += group->cpu_power;
|
|
group = group->next;
|
|
} while (group != child->groups);
|
|
|
|
sdg->cpu_power = power;
|
|
}
|
|
|
|
/**
|
|
* update_sg_lb_stats - Update sched_group's statistics for load balancing.
|
|
* @sd: The sched_domain whose statistics are to be updated.
|
|
* @group: sched_group whose statistics are to be updated.
|
|
* @this_cpu: Cpu for which load balance is currently performed.
|
|
* @idle: Idle status of this_cpu
|
|
* @load_idx: Load index of sched_domain of this_cpu for load calc.
|
|
* @sd_idle: Idle status of the sched_domain containing group.
|
|
* @local_group: Does group contain this_cpu.
|
|
* @cpus: Set of cpus considered for load balancing.
|
|
* @balance: Should we balance.
|
|
* @sgs: variable to hold the statistics for this group.
|
|
*/
|
|
static inline void update_sg_lb_stats(struct sched_domain *sd,
|
|
struct sched_group *group, int this_cpu,
|
|
enum cpu_idle_type idle, int load_idx, int *sd_idle,
|
|
int local_group, const struct cpumask *cpus,
|
|
int *balance, struct sg_lb_stats *sgs)
|
|
{
|
|
unsigned long load, max_cpu_load, min_cpu_load;
|
|
int i;
|
|
unsigned int balance_cpu = -1, first_idle_cpu = 0;
|
|
unsigned long sum_avg_load_per_task;
|
|
unsigned long avg_load_per_task;
|
|
|
|
if (local_group)
|
|
balance_cpu = group_first_cpu(group);
|
|
|
|
/* Tally up the load of all CPUs in the group */
|
|
sum_avg_load_per_task = avg_load_per_task = 0;
|
|
max_cpu_load = 0;
|
|
min_cpu_load = ~0UL;
|
|
|
|
for_each_cpu_and(i, sched_group_cpus(group), cpus) {
|
|
struct rq *rq = cpu_rq(i);
|
|
|
|
if (*sd_idle && rq->nr_running)
|
|
*sd_idle = 0;
|
|
|
|
/* Bias balancing toward cpus of our domain */
|
|
if (local_group) {
|
|
if (idle_cpu(i) && !first_idle_cpu) {
|
|
first_idle_cpu = 1;
|
|
balance_cpu = i;
|
|
}
|
|
|
|
load = target_load(i, load_idx);
|
|
} else {
|
|
load = source_load(i, load_idx);
|
|
if (load > max_cpu_load)
|
|
max_cpu_load = load;
|
|
if (min_cpu_load > load)
|
|
min_cpu_load = load;
|
|
}
|
|
|
|
sgs->group_load += load;
|
|
sgs->sum_nr_running += rq->nr_running;
|
|
sgs->sum_weighted_load += weighted_cpuload(i);
|
|
|
|
sum_avg_load_per_task += cpu_avg_load_per_task(i);
|
|
}
|
|
|
|
/*
|
|
* First idle cpu or the first cpu(busiest) in this sched group
|
|
* is eligible for doing load balancing at this and above
|
|
* domains. In the newly idle case, we will allow all the cpu's
|
|
* to do the newly idle load balance.
|
|
*/
|
|
if (idle != CPU_NEWLY_IDLE && local_group &&
|
|
balance_cpu != this_cpu) {
|
|
*balance = 0;
|
|
return;
|
|
}
|
|
|
|
update_group_power(sd, this_cpu);
|
|
|
|
/* Adjust by relative CPU power of the group */
|
|
sgs->avg_load = (sgs->group_load * SCHED_LOAD_SCALE) / group->cpu_power;
|
|
|
|
|
|
/*
|
|
* Consider the group unbalanced when the imbalance is larger
|
|
* than the average weight of two tasks.
|
|
*
|
|
* APZ: with cgroup the avg task weight can vary wildly and
|
|
* might not be a suitable number - should we keep a
|
|
* normalized nr_running number somewhere that negates
|
|
* the hierarchy?
|
|
*/
|
|
avg_load_per_task = (sum_avg_load_per_task * SCHED_LOAD_SCALE) /
|
|
group->cpu_power;
|
|
|
|
if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task)
|
|
sgs->group_imb = 1;
|
|
|
|
sgs->group_capacity =
|
|
DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE);
|
|
}
|
|
|
|
/**
|
|
* update_sd_lb_stats - Update sched_group's statistics for load balancing.
|
|
* @sd: sched_domain whose statistics are to be updated.
|
|
* @this_cpu: Cpu for which load balance is currently performed.
|
|
* @idle: Idle status of this_cpu
|
|
* @sd_idle: Idle status of the sched_domain containing group.
|
|
* @cpus: Set of cpus considered for load balancing.
|
|
* @balance: Should we balance.
|
|
* @sds: variable to hold the statistics for this sched_domain.
|
|
*/
|
|
static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
|
|
enum cpu_idle_type idle, int *sd_idle,
|
|
const struct cpumask *cpus, int *balance,
|
|
struct sd_lb_stats *sds)
|
|
{
|
|
struct sched_domain *child = sd->child;
|
|
struct sched_group *group = sd->groups;
|
|
struct sg_lb_stats sgs;
|
|
int load_idx, prefer_sibling = 0;
|
|
|
|
if (child && child->flags & SD_PREFER_SIBLING)
|
|
prefer_sibling = 1;
|
|
|
|
init_sd_power_savings_stats(sd, sds, idle);
|
|
load_idx = get_sd_load_idx(sd, idle);
|
|
|
|
do {
|
|
int local_group;
|
|
|
|
local_group = cpumask_test_cpu(this_cpu,
|
|
sched_group_cpus(group));
|
|
memset(&sgs, 0, sizeof(sgs));
|
|
update_sg_lb_stats(sd, group, this_cpu, idle, load_idx, sd_idle,
|
|
local_group, cpus, balance, &sgs);
|
|
|
|
if (local_group && !(*balance))
|
|
return;
|
|
|
|
sds->total_load += sgs.group_load;
|
|
sds->total_pwr += group->cpu_power;
|
|
|
|
/*
|
|
* In case the child domain prefers tasks go to siblings
|
|
* first, lower the group capacity to one so that we'll try
|
|
* and move all the excess tasks away.
|
|
*/
|
|
if (prefer_sibling)
|
|
sgs.group_capacity = min(sgs.group_capacity, 1UL);
|
|
|
|
if (local_group) {
|
|
sds->this_load = sgs.avg_load;
|
|
sds->this = group;
|
|
sds->this_nr_running = sgs.sum_nr_running;
|
|
sds->this_load_per_task = sgs.sum_weighted_load;
|
|
} else if (sgs.avg_load > sds->max_load &&
|
|
(sgs.sum_nr_running > sgs.group_capacity ||
|
|
sgs.group_imb)) {
|
|
sds->max_load = sgs.avg_load;
|
|
sds->busiest = group;
|
|
sds->busiest_nr_running = sgs.sum_nr_running;
|
|
sds->busiest_load_per_task = sgs.sum_weighted_load;
|
|
sds->group_imb = sgs.group_imb;
|
|
}
|
|
|
|
update_sd_power_savings_stats(group, sds, local_group, &sgs);
|
|
group = group->next;
|
|
} while (group != sd->groups);
|
|
}
|
|
|
|
/**
|
|
* fix_small_imbalance - Calculate the minor imbalance that exists
|
|
* amongst the groups of a sched_domain, during
|
|
* load balancing.
|
|
* @sds: Statistics of the sched_domain whose imbalance is to be calculated.
|
|
* @this_cpu: The cpu at whose sched_domain we're performing load-balance.
|
|
* @imbalance: Variable to store the imbalance.
|
|
*/
|
|
static inline void fix_small_imbalance(struct sd_lb_stats *sds,
|
|
int this_cpu, unsigned long *imbalance)
|
|
{
|
|
unsigned long tmp, pwr_now = 0, pwr_move = 0;
|
|
unsigned int imbn = 2;
|
|
|
|
if (sds->this_nr_running) {
|
|
sds->this_load_per_task /= sds->this_nr_running;
|
|
if (sds->busiest_load_per_task >
|
|
sds->this_load_per_task)
|
|
imbn = 1;
|
|
} else
|
|
sds->this_load_per_task =
|
|
cpu_avg_load_per_task(this_cpu);
|
|
|
|
if (sds->max_load - sds->this_load + sds->busiest_load_per_task >=
|
|
sds->busiest_load_per_task * imbn) {
|
|
*imbalance = sds->busiest_load_per_task;
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* OK, we don't have enough imbalance to justify moving tasks,
|
|
* however we may be able to increase total CPU power used by
|
|
* moving them.
|
|
*/
|
|
|
|
pwr_now += sds->busiest->cpu_power *
|
|
min(sds->busiest_load_per_task, sds->max_load);
|
|
pwr_now += sds->this->cpu_power *
|
|
min(sds->this_load_per_task, sds->this_load);
|
|
pwr_now /= SCHED_LOAD_SCALE;
|
|
|
|
/* Amount of load we'd subtract */
|
|
tmp = (sds->busiest_load_per_task * SCHED_LOAD_SCALE) /
|
|
sds->busiest->cpu_power;
|
|
if (sds->max_load > tmp)
|
|
pwr_move += sds->busiest->cpu_power *
|
|
min(sds->busiest_load_per_task, sds->max_load - tmp);
|
|
|
|
/* Amount of load we'd add */
|
|
if (sds->max_load * sds->busiest->cpu_power <
|
|
sds->busiest_load_per_task * SCHED_LOAD_SCALE)
|
|
tmp = (sds->max_load * sds->busiest->cpu_power) /
|
|
sds->this->cpu_power;
|
|
else
|
|
tmp = (sds->busiest_load_per_task * SCHED_LOAD_SCALE) /
|
|
sds->this->cpu_power;
|
|
pwr_move += sds->this->cpu_power *
|
|
min(sds->this_load_per_task, sds->this_load + tmp);
|
|
pwr_move /= SCHED_LOAD_SCALE;
|
|
|
|
/* Move if we gain throughput */
|
|
if (pwr_move > pwr_now)
|
|
*imbalance = sds->busiest_load_per_task;
|
|
}
|
|
|
|
/**
|
|
* calculate_imbalance - Calculate the amount of imbalance present within the
|
|
* groups of a given sched_domain during load balance.
|
|
* @sds: statistics of the sched_domain whose imbalance is to be calculated.
|
|
* @this_cpu: Cpu for which currently load balance is being performed.
|
|
* @imbalance: The variable to store the imbalance.
|
|
*/
|
|
static inline void calculate_imbalance(struct sd_lb_stats *sds, int this_cpu,
|
|
unsigned long *imbalance)
|
|
{
|
|
unsigned long max_pull;
|
|
/*
|
|
* In the presence of smp nice balancing, certain scenarios can have
|
|
* max load less than avg load(as we skip the groups at or below
|
|
* its cpu_power, while calculating max_load..)
|
|
*/
|
|
if (sds->max_load < sds->avg_load) {
|
|
*imbalance = 0;
|
|
return fix_small_imbalance(sds, this_cpu, imbalance);
|
|
}
|
|
|
|
/* Don't want to pull so many tasks that a group would go idle */
|
|
max_pull = min(sds->max_load - sds->avg_load,
|
|
sds->max_load - sds->busiest_load_per_task);
|
|
|
|
/* How much load to actually move to equalise the imbalance */
|
|
*imbalance = min(max_pull * sds->busiest->cpu_power,
|
|
(sds->avg_load - sds->this_load) * sds->this->cpu_power)
|
|
/ SCHED_LOAD_SCALE;
|
|
|
|
/*
|
|
* if *imbalance is less than the average load per runnable task
|
|
* there is no gaurantee that any tasks will be moved so we'll have
|
|
* a think about bumping its value to force at least one task to be
|
|
* moved
|
|
*/
|
|
if (*imbalance < sds->busiest_load_per_task)
|
|
return fix_small_imbalance(sds, this_cpu, imbalance);
|
|
|
|
}
|
|
/******* find_busiest_group() helpers end here *********************/
|
|
|
|
/**
|
|
* find_busiest_group - Returns the busiest group within the sched_domain
|
|
* if there is an imbalance. If there isn't an imbalance, and
|
|
* the user has opted for power-savings, it returns a group whose
|
|
* CPUs can be put to idle by rebalancing those tasks elsewhere, if
|
|
* such a group exists.
|
|
*
|
|
* Also calculates the amount of weighted load which should be moved
|
|
* to restore balance.
|
|
*
|
|
* @sd: The sched_domain whose busiest group is to be returned.
|
|
* @this_cpu: The cpu for which load balancing is currently being performed.
|
|
* @imbalance: Variable which stores amount of weighted load which should
|
|
* be moved to restore balance/put a group to idle.
|
|
* @idle: The idle status of this_cpu.
|
|
* @sd_idle: The idleness of sd
|
|
* @cpus: The set of CPUs under consideration for load-balancing.
|
|
* @balance: Pointer to a variable indicating if this_cpu
|
|
* is the appropriate cpu to perform load balancing at this_level.
|
|
*
|
|
* Returns: - the busiest group if imbalance exists.
|
|
* - If no imbalance and user has opted for power-savings balance,
|
|
* return the least loaded group whose CPUs can be
|
|
* put to idle by rebalancing its tasks onto our group.
|
|
*/
|
|
static struct sched_group *
|
|
find_busiest_group(struct sched_domain *sd, int this_cpu,
|
|
unsigned long *imbalance, enum cpu_idle_type idle,
|
|
int *sd_idle, const struct cpumask *cpus, int *balance)
|
|
{
|
|
struct sd_lb_stats sds;
|
|
|
|
memset(&sds, 0, sizeof(sds));
|
|
|
|
/*
|
|
* Compute the various statistics relavent for load balancing at
|
|
* this level.
|
|
*/
|
|
update_sd_lb_stats(sd, this_cpu, idle, sd_idle, cpus,
|
|
balance, &sds);
|
|
|
|
/* Cases where imbalance does not exist from POV of this_cpu */
|
|
/* 1) this_cpu is not the appropriate cpu to perform load balancing
|
|
* at this level.
|
|
* 2) There is no busy sibling group to pull from.
|
|
* 3) This group is the busiest group.
|
|
* 4) This group is more busy than the avg busieness at this
|
|
* sched_domain.
|
|
* 5) The imbalance is within the specified limit.
|
|
* 6) Any rebalance would lead to ping-pong
|
|
*/
|
|
if (!(*balance))
|
|
goto ret;
|
|
|
|
if (!sds.busiest || sds.busiest_nr_running == 0)
|
|
goto out_balanced;
|
|
|
|
if (sds.this_load >= sds.max_load)
|
|
goto out_balanced;
|
|
|
|
sds.avg_load = (SCHED_LOAD_SCALE * sds.total_load) / sds.total_pwr;
|
|
|
|
if (sds.this_load >= sds.avg_load)
|
|
goto out_balanced;
|
|
|
|
if (100 * sds.max_load <= sd->imbalance_pct * sds.this_load)
|
|
goto out_balanced;
|
|
|
|
sds.busiest_load_per_task /= sds.busiest_nr_running;
|
|
if (sds.group_imb)
|
|
sds.busiest_load_per_task =
|
|
min(sds.busiest_load_per_task, sds.avg_load);
|
|
|
|
/*
|
|
* We're trying to get all the cpus to the average_load, so we don't
|
|
* want to push ourselves above the average load, nor do we wish to
|
|
* reduce the max loaded cpu below the average load, as either of these
|
|
* actions would just result in more rebalancing later, and ping-pong
|
|
* tasks around. Thus we look for the minimum possible imbalance.
|
|
* Negative imbalances (*we* are more loaded than anyone else) will
|
|
* be counted as no imbalance for these purposes -- we can't fix that
|
|
* by pulling tasks to us. Be careful of negative numbers as they'll
|
|
* appear as very large values with unsigned longs.
|
|
*/
|
|
if (sds.max_load <= sds.busiest_load_per_task)
|
|
goto out_balanced;
|
|
|
|
/* Looks like there is an imbalance. Compute it */
|
|
calculate_imbalance(&sds, this_cpu, imbalance);
|
|
return sds.busiest;
|
|
|
|
out_balanced:
|
|
/*
|
|
* There is no obvious imbalance. But check if we can do some balancing
|
|
* to save power.
|
|
*/
|
|
if (check_power_save_busiest_group(&sds, this_cpu, imbalance))
|
|
return sds.busiest;
|
|
ret:
|
|
*imbalance = 0;
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* find_busiest_queue - find the busiest runqueue among the cpus in group.
|
|
*/
|
|
static struct rq *
|
|
find_busiest_queue(struct sched_group *group, enum cpu_idle_type idle,
|
|
unsigned long imbalance, const struct cpumask *cpus)
|
|
{
|
|
struct rq *busiest = NULL, *rq;
|
|
unsigned long max_load = 0;
|
|
int i;
|
|
|
|
for_each_cpu(i, sched_group_cpus(group)) {
|
|
unsigned long power = power_of(i);
|
|
unsigned long capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
|
|
unsigned long wl;
|
|
|
|
if (!cpumask_test_cpu(i, cpus))
|
|
continue;
|
|
|
|
rq = cpu_rq(i);
|
|
wl = weighted_cpuload(i) * SCHED_LOAD_SCALE;
|
|
wl /= power;
|
|
|
|
if (capacity && rq->nr_running == 1 && wl > imbalance)
|
|
continue;
|
|
|
|
if (wl > max_load) {
|
|
max_load = wl;
|
|
busiest = rq;
|
|
}
|
|
}
|
|
|
|
return busiest;
|
|
}
|
|
|
|
/*
|
|
* Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
|
|
* so long as it is large enough.
|
|
*/
|
|
#define MAX_PINNED_INTERVAL 512
|
|
|
|
/* Working cpumask for load_balance and load_balance_newidle. */
|
|
static DEFINE_PER_CPU(cpumask_var_t, load_balance_tmpmask);
|
|
|
|
static int need_active_balance(struct sched_domain *sd, int sd_idle, int idle)
|
|
{
|
|
if (idle == CPU_NEWLY_IDLE) {
|
|
/*
|
|
* The only task running in a non-idle cpu can be moved to this
|
|
* cpu in an attempt to completely freeup the other CPU
|
|
* package.
|
|
*
|
|
* The package power saving logic comes from
|
|
* find_busiest_group(). If there are no imbalance, then
|
|
* f_b_g() will return NULL. However when sched_mc={1,2} then
|
|
* f_b_g() will select a group from which a running task may be
|
|
* pulled to this cpu in order to make the other package idle.
|
|
* If there is no opportunity to make a package idle and if
|
|
* there are no imbalance, then f_b_g() will return NULL and no
|
|
* action will be taken in load_balance_newidle().
|
|
*
|
|
* Under normal task pull operation due to imbalance, there
|
|
* will be more than one task in the source run queue and
|
|
* move_tasks() will succeed. ld_moved will be true and this
|
|
* active balance code will not be triggered.
|
|
*/
|
|
if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
|
|
!test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
|
|
return 0;
|
|
|
|
if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP)
|
|
return 0;
|
|
}
|
|
|
|
return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
|
|
}
|
|
|
|
/*
|
|
* Check this_cpu to ensure it is balanced within domain. Attempt to move
|
|
* tasks if there is an imbalance.
|
|
*/
|
|
static int load_balance(int this_cpu, struct rq *this_rq,
|
|
struct sched_domain *sd, enum cpu_idle_type idle,
|
|
int *balance)
|
|
{
|
|
int ld_moved, all_pinned = 0, active_balance = 0, sd_idle = 0;
|
|
struct sched_group *group;
|
|
unsigned long imbalance;
|
|
struct rq *busiest;
|
|
unsigned long flags;
|
|
struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);
|
|
|
|
cpumask_copy(cpus, cpu_active_mask);
|
|
|
|
/*
|
|
* When power savings policy is enabled for the parent domain, idle
|
|
* sibling can pick up load irrespective of busy siblings. In this case,
|
|
* let the state of idle sibling percolate up as CPU_IDLE, instead of
|
|
* portraying it as CPU_NOT_IDLE.
|
|
*/
|
|
if (idle != CPU_NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER &&
|
|
!test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
|
|
sd_idle = 1;
|
|
|
|
schedstat_inc(sd, lb_count[idle]);
|
|
|
|
redo:
|
|
update_shares(sd);
|
|
group = find_busiest_group(sd, this_cpu, &imbalance, idle, &sd_idle,
|
|
cpus, balance);
|
|
|
|
if (*balance == 0)
|
|
goto out_balanced;
|
|
|
|
if (!group) {
|
|
schedstat_inc(sd, lb_nobusyg[idle]);
|
|
goto out_balanced;
|
|
}
|
|
|
|
busiest = find_busiest_queue(group, idle, imbalance, cpus);
|
|
if (!busiest) {
|
|
schedstat_inc(sd, lb_nobusyq[idle]);
|
|
goto out_balanced;
|
|
}
|
|
|
|
BUG_ON(busiest == this_rq);
|
|
|
|
schedstat_add(sd, lb_imbalance[idle], imbalance);
|
|
|
|
ld_moved = 0;
|
|
if (busiest->nr_running > 1) {
|
|
/*
|
|
* Attempt to move tasks. If find_busiest_group has found
|
|
* an imbalance but busiest->nr_running <= 1, the group is
|
|
* still unbalanced. ld_moved simply stays zero, so it is
|
|
* correctly treated as an imbalance.
|
|
*/
|
|
local_irq_save(flags);
|
|
double_rq_lock(this_rq, busiest);
|
|
ld_moved = move_tasks(this_rq, this_cpu, busiest,
|
|
imbalance, sd, idle, &all_pinned);
|
|
double_rq_unlock(this_rq, busiest);
|
|
local_irq_restore(flags);
|
|
|
|
/*
|
|
* some other cpu did the load balance for us.
|
|
*/
|
|
if (ld_moved && this_cpu != smp_processor_id())
|
|
resched_cpu(this_cpu);
|
|
|
|
/* All tasks on this runqueue were pinned by CPU affinity */
|
|
if (unlikely(all_pinned)) {
|
|
cpumask_clear_cpu(cpu_of(busiest), cpus);
|
|
if (!cpumask_empty(cpus))
|
|
goto redo;
|
|
goto out_balanced;
|
|
}
|
|
}
|
|
|
|
if (!ld_moved) {
|
|
schedstat_inc(sd, lb_failed[idle]);
|
|
sd->nr_balance_failed++;
|
|
|
|
if (need_active_balance(sd, sd_idle, idle)) {
|
|
raw_spin_lock_irqsave(&busiest->lock, flags);
|
|
|
|
/* don't kick the migration_thread, if the curr
|
|
* task on busiest cpu can't be moved to this_cpu
|
|
*/
|
|
if (!cpumask_test_cpu(this_cpu,
|
|
&busiest->curr->cpus_allowed)) {
|
|
raw_spin_unlock_irqrestore(&busiest->lock,
|
|
flags);
|
|
all_pinned = 1;
|
|
goto out_one_pinned;
|
|
}
|
|
|
|
if (!busiest->active_balance) {
|
|
busiest->active_balance = 1;
|
|
busiest->push_cpu = this_cpu;
|
|
active_balance = 1;
|
|
}
|
|
raw_spin_unlock_irqrestore(&busiest->lock, flags);
|
|
if (active_balance)
|
|
wake_up_process(busiest->migration_thread);
|
|
|
|
/*
|
|
* We've kicked active balancing, reset the failure
|
|
* counter.
|
|
*/
|
|
sd->nr_balance_failed = sd->cache_nice_tries+1;
|
|
}
|
|
} else
|
|
sd->nr_balance_failed = 0;
|
|
|
|
if (likely(!active_balance)) {
|
|
/* We were unbalanced, so reset the balancing interval */
|
|
sd->balance_interval = sd->min_interval;
|
|
} else {
|
|
/*
|
|
* If we've begun active balancing, start to back off. This
|
|
* case may not be covered by the all_pinned logic if there
|
|
* is only 1 task on the busy runqueue (because we don't call
|
|
* move_tasks).
|
|
*/
|
|
if (sd->balance_interval < sd->max_interval)
|
|
sd->balance_interval *= 2;
|
|
}
|
|
|
|
if (!ld_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
|
|
!test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
|
|
ld_moved = -1;
|
|
|
|
goto out;
|
|
|
|
out_balanced:
|
|
schedstat_inc(sd, lb_balanced[idle]);
|
|
|
|
sd->nr_balance_failed = 0;
|
|
|
|
out_one_pinned:
|
|
/* tune up the balancing interval */
|
|
if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) ||
|
|
(sd->balance_interval < sd->max_interval))
|
|
sd->balance_interval *= 2;
|
|
|
|
if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
|
|
!test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
|
|
ld_moved = -1;
|
|
else
|
|
ld_moved = 0;
|
|
out:
|
|
if (ld_moved)
|
|
update_shares(sd);
|
|
return ld_moved;
|
|
}
|
|
|
|
/*
|
|
* idle_balance is called by schedule() if this_cpu is about to become
|
|
* idle. Attempts to pull tasks from other CPUs.
|
|
*/
|
|
static void idle_balance(int this_cpu, struct rq *this_rq)
|
|
{
|
|
struct sched_domain *sd;
|
|
int pulled_task = 0;
|
|
unsigned long next_balance = jiffies + HZ;
|
|
|
|
this_rq->idle_stamp = this_rq->clock;
|
|
|
|
if (this_rq->avg_idle < sysctl_sched_migration_cost)
|
|
return;
|
|
|
|
/*
|
|
* Drop the rq->lock, but keep IRQ/preempt disabled.
|
|
*/
|
|
raw_spin_unlock(&this_rq->lock);
|
|
|
|
for_each_domain(this_cpu, sd) {
|
|
unsigned long interval;
|
|
int balance = 1;
|
|
|
|
if (!(sd->flags & SD_LOAD_BALANCE))
|
|
continue;
|
|
|
|
if (sd->flags & SD_BALANCE_NEWIDLE) {
|
|
/* If we've pulled tasks over stop searching: */
|
|
pulled_task = load_balance(this_cpu, this_rq,
|
|
sd, CPU_NEWLY_IDLE, &balance);
|
|
}
|
|
|
|
interval = msecs_to_jiffies(sd->balance_interval);
|
|
if (time_after(next_balance, sd->last_balance + interval))
|
|
next_balance = sd->last_balance + interval;
|
|
if (pulled_task) {
|
|
this_rq->idle_stamp = 0;
|
|
break;
|
|
}
|
|
}
|
|
|
|
raw_spin_lock(&this_rq->lock);
|
|
|
|
if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
|
|
/*
|
|
* We are going idle. next_balance may be set based on
|
|
* a busy processor. So reset next_balance.
|
|
*/
|
|
this_rq->next_balance = next_balance;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* active_load_balance is run by migration threads. It pushes running tasks
|
|
* off the busiest CPU onto idle CPUs. It requires at least 1 task to be
|
|
* running on each physical CPU where possible, and avoids physical /
|
|
* logical imbalances.
|
|
*
|
|
* Called with busiest_rq locked.
|
|
*/
|
|
static void active_load_balance(struct rq *busiest_rq, int busiest_cpu)
|
|
{
|
|
int target_cpu = busiest_rq->push_cpu;
|
|
struct sched_domain *sd;
|
|
struct rq *target_rq;
|
|
|
|
/* Is there any task to move? */
|
|
if (busiest_rq->nr_running <= 1)
|
|
return;
|
|
|
|
target_rq = cpu_rq(target_cpu);
|
|
|
|
/*
|
|
* This condition is "impossible", if it occurs
|
|
* we need to fix it. Originally reported by
|
|
* Bjorn Helgaas on a 128-cpu setup.
|
|
*/
|
|
BUG_ON(busiest_rq == target_rq);
|
|
|
|
/* move a task from busiest_rq to target_rq */
|
|
double_lock_balance(busiest_rq, target_rq);
|
|
update_rq_clock(busiest_rq);
|
|
update_rq_clock(target_rq);
|
|
|
|
/* Search for an sd spanning us and the target CPU. */
|
|
for_each_domain(target_cpu, sd) {
|
|
if ((sd->flags & SD_LOAD_BALANCE) &&
|
|
cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
|
|
break;
|
|
}
|
|
|
|
if (likely(sd)) {
|
|
schedstat_inc(sd, alb_count);
|
|
|
|
if (move_one_task(target_rq, target_cpu, busiest_rq,
|
|
sd, CPU_IDLE))
|
|
schedstat_inc(sd, alb_pushed);
|
|
else
|
|
schedstat_inc(sd, alb_failed);
|
|
}
|
|
double_unlock_balance(busiest_rq, target_rq);
|
|
}
|
|
|
|
#ifdef CONFIG_NO_HZ
|
|
static struct {
|
|
atomic_t load_balancer;
|
|
cpumask_var_t cpu_mask;
|
|
cpumask_var_t ilb_grp_nohz_mask;
|
|
} nohz ____cacheline_aligned = {
|
|
.load_balancer = ATOMIC_INIT(-1),
|
|
};
|
|
|
|
int get_nohz_load_balancer(void)
|
|
{
|
|
return atomic_read(&nohz.load_balancer);
|
|
}
|
|
|
|
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
|
|
/**
|
|
* lowest_flag_domain - Return lowest sched_domain containing flag.
|
|
* @cpu: The cpu whose lowest level of sched domain is to
|
|
* be returned.
|
|
* @flag: The flag to check for the lowest sched_domain
|
|
* for the given cpu.
|
|
*
|
|
* Returns the lowest sched_domain of a cpu which contains the given flag.
|
|
*/
|
|
static inline struct sched_domain *lowest_flag_domain(int cpu, int flag)
|
|
{
|
|
struct sched_domain *sd;
|
|
|
|
for_each_domain(cpu, sd)
|
|
if (sd && (sd->flags & flag))
|
|
break;
|
|
|
|
return sd;
|
|
}
|
|
|
|
/**
|
|
* for_each_flag_domain - Iterates over sched_domains containing the flag.
|
|
* @cpu: The cpu whose domains we're iterating over.
|
|
* @sd: variable holding the value of the power_savings_sd
|
|
* for cpu.
|
|
* @flag: The flag to filter the sched_domains to be iterated.
|
|
*
|
|
* Iterates over all the scheduler domains for a given cpu that has the 'flag'
|
|
* set, starting from the lowest sched_domain to the highest.
|
|
*/
|
|
#define for_each_flag_domain(cpu, sd, flag) \
|
|
for (sd = lowest_flag_domain(cpu, flag); \
|
|
(sd && (sd->flags & flag)); sd = sd->parent)
|
|
|
|
/**
|
|
* is_semi_idle_group - Checks if the given sched_group is semi-idle.
|
|
* @ilb_group: group to be checked for semi-idleness
|
|
*
|
|
* Returns: 1 if the group is semi-idle. 0 otherwise.
|
|
*
|
|
* We define a sched_group to be semi idle if it has atleast one idle-CPU
|
|
* and atleast one non-idle CPU. This helper function checks if the given
|
|
* sched_group is semi-idle or not.
|
|
*/
|
|
static inline int is_semi_idle_group(struct sched_group *ilb_group)
|
|
{
|
|
cpumask_and(nohz.ilb_grp_nohz_mask, nohz.cpu_mask,
|
|
sched_group_cpus(ilb_group));
|
|
|
|
/*
|
|
* A sched_group is semi-idle when it has atleast one busy cpu
|
|
* and atleast one idle cpu.
|
|
*/
|
|
if (cpumask_empty(nohz.ilb_grp_nohz_mask))
|
|
return 0;
|
|
|
|
if (cpumask_equal(nohz.ilb_grp_nohz_mask, sched_group_cpus(ilb_group)))
|
|
return 0;
|
|
|
|
return 1;
|
|
}
|
|
/**
|
|
* find_new_ilb - Finds the optimum idle load balancer for nomination.
|
|
* @cpu: The cpu which is nominating a new idle_load_balancer.
|
|
*
|
|
* Returns: Returns the id of the idle load balancer if it exists,
|
|
* Else, returns >= nr_cpu_ids.
|
|
*
|
|
* This algorithm picks the idle load balancer such that it belongs to a
|
|
* semi-idle powersavings sched_domain. The idea is to try and avoid
|
|
* completely idle packages/cores just for the purpose of idle load balancing
|
|
* when there are other idle cpu's which are better suited for that job.
|
|
*/
|
|
static int find_new_ilb(int cpu)
|
|
{
|
|
struct sched_domain *sd;
|
|
struct sched_group *ilb_group;
|
|
|
|
/*
|
|
* Have idle load balancer selection from semi-idle packages only
|
|
* when power-aware load balancing is enabled
|
|
*/
|
|
if (!(sched_smt_power_savings || sched_mc_power_savings))
|
|
goto out_done;
|
|
|
|
/*
|
|
* Optimize for the case when we have no idle CPUs or only one
|
|
* idle CPU. Don't walk the sched_domain hierarchy in such cases
|
|
*/
|
|
if (cpumask_weight(nohz.cpu_mask) < 2)
|
|
goto out_done;
|
|
|
|
for_each_flag_domain(cpu, sd, SD_POWERSAVINGS_BALANCE) {
|
|
ilb_group = sd->groups;
|
|
|
|
do {
|
|
if (is_semi_idle_group(ilb_group))
|
|
return cpumask_first(nohz.ilb_grp_nohz_mask);
|
|
|
|
ilb_group = ilb_group->next;
|
|
|
|
} while (ilb_group != sd->groups);
|
|
}
|
|
|
|
out_done:
|
|
return cpumask_first(nohz.cpu_mask);
|
|
}
|
|
#else /* (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */
|
|
static inline int find_new_ilb(int call_cpu)
|
|
{
|
|
return cpumask_first(nohz.cpu_mask);
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* This routine will try to nominate the ilb (idle load balancing)
|
|
* owner among the cpus whose ticks are stopped. ilb owner will do the idle
|
|
* load balancing on behalf of all those cpus. If all the cpus in the system
|
|
* go into this tickless mode, then there will be no ilb owner (as there is
|
|
* no need for one) and all the cpus will sleep till the next wakeup event
|
|
* arrives...
|
|
*
|
|
* For the ilb owner, tick is not stopped. And this tick will be used
|
|
* for idle load balancing. ilb owner will still be part of
|
|
* nohz.cpu_mask..
|
|
*
|
|
* While stopping the tick, this cpu will become the ilb owner if there
|
|
* is no other owner. And will be the owner till that cpu becomes busy
|
|
* or if all cpus in the system stop their ticks at which point
|
|
* there is no need for ilb owner.
|
|
*
|
|
* When the ilb owner becomes busy, it nominates another owner, during the
|
|
* next busy scheduler_tick()
|
|
*/
|
|
int select_nohz_load_balancer(int stop_tick)
|
|
{
|
|
int cpu = smp_processor_id();
|
|
|
|
if (stop_tick) {
|
|
cpu_rq(cpu)->in_nohz_recently = 1;
|
|
|
|
if (!cpu_active(cpu)) {
|
|
if (atomic_read(&nohz.load_balancer) != cpu)
|
|
return 0;
|
|
|
|
/*
|
|
* If we are going offline and still the leader,
|
|
* give up!
|
|
*/
|
|
if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
|
|
BUG();
|
|
|
|
return 0;
|
|
}
|
|
|
|
cpumask_set_cpu(cpu, nohz.cpu_mask);
|
|
|
|
/* time for ilb owner also to sleep */
|
|
if (cpumask_weight(nohz.cpu_mask) == num_active_cpus()) {
|
|
if (atomic_read(&nohz.load_balancer) == cpu)
|
|
atomic_set(&nohz.load_balancer, -1);
|
|
return 0;
|
|
}
|
|
|
|
if (atomic_read(&nohz.load_balancer) == -1) {
|
|
/* make me the ilb owner */
|
|
if (atomic_cmpxchg(&nohz.load_balancer, -1, cpu) == -1)
|
|
return 1;
|
|
} else if (atomic_read(&nohz.load_balancer) == cpu) {
|
|
int new_ilb;
|
|
|
|
if (!(sched_smt_power_savings ||
|
|
sched_mc_power_savings))
|
|
return 1;
|
|
/*
|
|
* Check to see if there is a more power-efficient
|
|
* ilb.
|
|
*/
|
|
new_ilb = find_new_ilb(cpu);
|
|
if (new_ilb < nr_cpu_ids && new_ilb != cpu) {
|
|
atomic_set(&nohz.load_balancer, -1);
|
|
resched_cpu(new_ilb);
|
|
return 0;
|
|
}
|
|
return 1;
|
|
}
|
|
} else {
|
|
if (!cpumask_test_cpu(cpu, nohz.cpu_mask))
|
|
return 0;
|
|
|
|
cpumask_clear_cpu(cpu, nohz.cpu_mask);
|
|
|
|
if (atomic_read(&nohz.load_balancer) == cpu)
|
|
if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
|
|
BUG();
|
|
}
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
static DEFINE_SPINLOCK(balancing);
|
|
|
|
/*
|
|
* It checks each scheduling domain to see if it is due to be balanced,
|
|
* and initiates a balancing operation if so.
|
|
*
|
|
* Balancing parameters are set up in arch_init_sched_domains.
|
|
*/
|
|
static void rebalance_domains(int cpu, enum cpu_idle_type idle)
|
|
{
|
|
int balance = 1;
|
|
struct rq *rq = cpu_rq(cpu);
|
|
unsigned long interval;
|
|
struct sched_domain *sd;
|
|
/* Earliest time when we have to do rebalance again */
|
|
unsigned long next_balance = jiffies + 60*HZ;
|
|
int update_next_balance = 0;
|
|
int need_serialize;
|
|
|
|
for_each_domain(cpu, sd) {
|
|
if (!(sd->flags & SD_LOAD_BALANCE))
|
|
continue;
|
|
|
|
interval = sd->balance_interval;
|
|
if (idle != CPU_IDLE)
|
|
interval *= sd->busy_factor;
|
|
|
|
/* scale ms to jiffies */
|
|
interval = msecs_to_jiffies(interval);
|
|
if (unlikely(!interval))
|
|
interval = 1;
|
|
if (interval > HZ*NR_CPUS/10)
|
|
interval = HZ*NR_CPUS/10;
|
|
|
|
need_serialize = sd->flags & SD_SERIALIZE;
|
|
|
|
if (need_serialize) {
|
|
if (!spin_trylock(&balancing))
|
|
goto out;
|
|
}
|
|
|
|
if (time_after_eq(jiffies, sd->last_balance + interval)) {
|
|
if (load_balance(cpu, rq, sd, idle, &balance)) {
|
|
/*
|
|
* We've pulled tasks over so either we're no
|
|
* longer idle, or one of our SMT siblings is
|
|
* not idle.
|
|
*/
|
|
idle = CPU_NOT_IDLE;
|
|
}
|
|
sd->last_balance = jiffies;
|
|
}
|
|
if (need_serialize)
|
|
spin_unlock(&balancing);
|
|
out:
|
|
if (time_after(next_balance, sd->last_balance + interval)) {
|
|
next_balance = sd->last_balance + interval;
|
|
update_next_balance = 1;
|
|
}
|
|
|
|
/*
|
|
* Stop the load balance at this level. There is another
|
|
* CPU in our sched group which is doing load balancing more
|
|
* actively.
|
|
*/
|
|
if (!balance)
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* next_balance will be updated only when there is a need.
|
|
* When the cpu is attached to null domain for ex, it will not be
|
|
* updated.
|
|
*/
|
|
if (likely(update_next_balance))
|
|
rq->next_balance = next_balance;
|
|
}
|
|
|
|
/*
|
|
* run_rebalance_domains is triggered when needed from the scheduler tick.
|
|
* In CONFIG_NO_HZ case, the idle load balance owner will do the
|
|
* rebalancing for all the cpus for whom scheduler ticks are stopped.
|
|
*/
|
|
static void run_rebalance_domains(struct softirq_action *h)
|
|
{
|
|
int this_cpu = smp_processor_id();
|
|
struct rq *this_rq = cpu_rq(this_cpu);
|
|
enum cpu_idle_type idle = this_rq->idle_at_tick ?
|
|
CPU_IDLE : CPU_NOT_IDLE;
|
|
|
|
rebalance_domains(this_cpu, idle);
|
|
|
|
#ifdef CONFIG_NO_HZ
|
|
/*
|
|
* If this cpu is the owner for idle load balancing, then do the
|
|
* balancing on behalf of the other idle cpus whose ticks are
|
|
* stopped.
|
|
*/
|
|
if (this_rq->idle_at_tick &&
|
|
atomic_read(&nohz.load_balancer) == this_cpu) {
|
|
struct rq *rq;
|
|
int balance_cpu;
|
|
|
|
for_each_cpu(balance_cpu, nohz.cpu_mask) {
|
|
if (balance_cpu == this_cpu)
|
|
continue;
|
|
|
|
/*
|
|
* If this cpu gets work to do, stop the load balancing
|
|
* work being done for other cpus. Next load
|
|
* balancing owner will pick it up.
|
|
*/
|
|
if (need_resched())
|
|
break;
|
|
|
|
rebalance_domains(balance_cpu, CPU_IDLE);
|
|
|
|
rq = cpu_rq(balance_cpu);
|
|
if (time_after(this_rq->next_balance, rq->next_balance))
|
|
this_rq->next_balance = rq->next_balance;
|
|
}
|
|
}
|
|
#endif
|
|
}
|
|
|
|
static inline int on_null_domain(int cpu)
|
|
{
|
|
return !rcu_dereference(cpu_rq(cpu)->sd);
|
|
}
|
|
|
|
/*
|
|
* Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
|
|
*
|
|
* In case of CONFIG_NO_HZ, this is the place where we nominate a new
|
|
* idle load balancing owner or decide to stop the periodic load balancing,
|
|
* if the whole system is idle.
|
|
*/
|
|
static inline void trigger_load_balance(struct rq *rq, int cpu)
|
|
{
|
|
#ifdef CONFIG_NO_HZ
|
|
/*
|
|
* If we were in the nohz mode recently and busy at the current
|
|
* scheduler tick, then check if we need to nominate new idle
|
|
* load balancer.
|
|
*/
|
|
if (rq->in_nohz_recently && !rq->idle_at_tick) {
|
|
rq->in_nohz_recently = 0;
|
|
|
|
if (atomic_read(&nohz.load_balancer) == cpu) {
|
|
cpumask_clear_cpu(cpu, nohz.cpu_mask);
|
|
atomic_set(&nohz.load_balancer, -1);
|
|
}
|
|
|
|
if (atomic_read(&nohz.load_balancer) == -1) {
|
|
int ilb = find_new_ilb(cpu);
|
|
|
|
if (ilb < nr_cpu_ids)
|
|
resched_cpu(ilb);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If this cpu is idle and doing idle load balancing for all the
|
|
* cpus with ticks stopped, is it time for that to stop?
|
|
*/
|
|
if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) == cpu &&
|
|
cpumask_weight(nohz.cpu_mask) == num_online_cpus()) {
|
|
resched_cpu(cpu);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* If this cpu is idle and the idle load balancing is done by
|
|
* someone else, then no need raise the SCHED_SOFTIRQ
|
|
*/
|
|
if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) != cpu &&
|
|
cpumask_test_cpu(cpu, nohz.cpu_mask))
|
|
return;
|
|
#endif
|
|
/* Don't need to rebalance while attached to NULL domain */
|
|
if (time_after_eq(jiffies, rq->next_balance) &&
|
|
likely(!on_null_domain(cpu)))
|
|
raise_softirq(SCHED_SOFTIRQ);
|
|
}
|
|
|
|
static void rq_online_fair(struct rq *rq)
|
|
{
|
|
update_sysctl();
|
|
}
|
|
|
|
static void rq_offline_fair(struct rq *rq)
|
|
{
|
|
update_sysctl();
|
|
}
|
|
|
|
#else /* CONFIG_SMP */
|
|
|
|
/*
|
|
* on UP we do not need to balance between CPUs:
|
|
*/
|
|
static inline void idle_balance(int cpu, struct rq *rq)
|
|
{
|
|
}
|
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
/*
|
|
* scheduler tick hitting a task of our scheduling class:
|
|
*/
|
|
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se = &curr->se;
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
entity_tick(cfs_rq, se, queued);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* called on fork with the child task as argument from the parent's context
|
|
* - child not yet on the tasklist
|
|
* - preemption disabled
|
|
*/
|
|
static void task_fork_fair(struct task_struct *p)
|
|
{
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(current);
|
|
struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
|
|
int this_cpu = smp_processor_id();
|
|
struct rq *rq = this_rq();
|
|
unsigned long flags;
|
|
|
|
raw_spin_lock_irqsave(&rq->lock, flags);
|
|
|
|
if (unlikely(task_cpu(p) != this_cpu))
|
|
__set_task_cpu(p, this_cpu);
|
|
|
|
update_curr(cfs_rq);
|
|
|
|
if (curr)
|
|
se->vruntime = curr->vruntime;
|
|
place_entity(cfs_rq, se, 1);
|
|
|
|
if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
|
|
/*
|
|
* Upon rescheduling, sched_class::put_prev_task() will place
|
|
* 'current' within the tree based on its new key value.
|
|
*/
|
|
swap(curr->vruntime, se->vruntime);
|
|
resched_task(rq->curr);
|
|
}
|
|
|
|
se->vruntime -= cfs_rq->min_vruntime;
|
|
|
|
raw_spin_unlock_irqrestore(&rq->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* Priority of the task has changed. Check to see if we preempt
|
|
* the current task.
|
|
*/
|
|
static void prio_changed_fair(struct rq *rq, struct task_struct *p,
|
|
int oldprio, int running)
|
|
{
|
|
/*
|
|
* Reschedule if we are currently running on this runqueue and
|
|
* our priority decreased, or if we are not currently running on
|
|
* this runqueue and our priority is higher than the current's
|
|
*/
|
|
if (running) {
|
|
if (p->prio > oldprio)
|
|
resched_task(rq->curr);
|
|
} else
|
|
check_preempt_curr(rq, p, 0);
|
|
}
|
|
|
|
/*
|
|
* We switched to the sched_fair class.
|
|
*/
|
|
static void switched_to_fair(struct rq *rq, struct task_struct *p,
|
|
int running)
|
|
{
|
|
/*
|
|
* We were most likely switched from sched_rt, so
|
|
* kick off the schedule if running, otherwise just see
|
|
* if we can still preempt the current task.
|
|
*/
|
|
if (running)
|
|
resched_task(rq->curr);
|
|
else
|
|
check_preempt_curr(rq, p, 0);
|
|
}
|
|
|
|
/* Account for a task changing its policy or group.
|
|
*
|
|
* This routine is mostly called to set cfs_rq->curr field when a task
|
|
* migrates between groups/classes.
|
|
*/
|
|
static void set_curr_task_fair(struct rq *rq)
|
|
{
|
|
struct sched_entity *se = &rq->curr->se;
|
|
|
|
for_each_sched_entity(se)
|
|
set_next_entity(cfs_rq_of(se), se);
|
|
}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
static void moved_group_fair(struct task_struct *p, int on_rq)
|
|
{
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(p);
|
|
|
|
update_curr(cfs_rq);
|
|
if (!on_rq)
|
|
place_entity(cfs_rq, &p->se, 1);
|
|
}
|
|
#endif
|
|
|
|
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
|
|
{
|
|
struct sched_entity *se = &task->se;
|
|
unsigned int rr_interval = 0;
|
|
|
|
/*
|
|
* Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
|
|
* idle runqueue:
|
|
*/
|
|
if (rq->cfs.load.weight)
|
|
rr_interval = NS_TO_JIFFIES(sched_slice(&rq->cfs, se));
|
|
|
|
return rr_interval;
|
|
}
|
|
|
|
/*
|
|
* All the scheduling class methods:
|
|
*/
|
|
static const struct sched_class fair_sched_class = {
|
|
.next = &idle_sched_class,
|
|
.enqueue_task = enqueue_task_fair,
|
|
.dequeue_task = dequeue_task_fair,
|
|
.yield_task = yield_task_fair,
|
|
|
|
.check_preempt_curr = check_preempt_wakeup,
|
|
|
|
.pick_next_task = pick_next_task_fair,
|
|
.put_prev_task = put_prev_task_fair,
|
|
|
|
#ifdef CONFIG_SMP
|
|
.select_task_rq = select_task_rq_fair,
|
|
|
|
.rq_online = rq_online_fair,
|
|
.rq_offline = rq_offline_fair,
|
|
|
|
.task_waking = task_waking_fair,
|
|
#endif
|
|
|
|
.set_curr_task = set_curr_task_fair,
|
|
.task_tick = task_tick_fair,
|
|
.task_fork = task_fork_fair,
|
|
|
|
.prio_changed = prio_changed_fair,
|
|
.switched_to = switched_to_fair,
|
|
|
|
.get_rr_interval = get_rr_interval_fair,
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
.moved_group = moved_group_fair,
|
|
#endif
|
|
};
|
|
|
|
#ifdef CONFIG_SCHED_DEBUG
|
|
static void print_cfs_stats(struct seq_file *m, int cpu)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
|
|
rcu_read_lock();
|
|
for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
|
|
print_cfs_rq(m, cpu, cfs_rq);
|
|
rcu_read_unlock();
|
|
}
|
|
#endif
|