2007-07-10 00:51:58 +08:00
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/*
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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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2007-08-26 00:41:53 +08:00
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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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2007-07-10 00:51:58 +08:00
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*/
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2008-01-26 04:08:34 +08:00
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#include <linux/latencytop.h>
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2007-07-10 00:51:58 +08:00
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/*
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2007-08-26 00:41:53 +08:00
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* Targeted preemption latency for CPU-bound tasks:
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2007-11-27 04:21:49 +08:00
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* (default: 20ms * (1 + ilog(ncpus)), units: nanoseconds)
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2007-07-10 00:51:58 +08:00
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*
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2007-08-26 00:41:53 +08:00
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* NOTE: this latency value is not the same as the concept of
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2007-10-15 23:00:14 +08:00
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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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2007-07-10 00:51:58 +08:00
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*
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2007-10-15 23:00:14 +08:00
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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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2007-07-10 00:51:58 +08:00
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*/
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2007-11-10 05:39:38 +08:00
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unsigned int sysctl_sched_latency = 20000000ULL;
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2007-10-15 23:00:02 +08:00
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/*
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2007-11-10 05:39:37 +08:00
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* Minimal preemption granularity for CPU-bound tasks:
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2007-11-27 04:21:49 +08:00
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* (default: 4 msec * (1 + ilog(ncpus)), units: nanoseconds)
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2007-10-15 23:00:02 +08:00
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*/
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2007-11-27 04:21:49 +08:00
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unsigned int sysctl_sched_min_granularity = 4000000ULL;
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2007-08-26 00:41:53 +08:00
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/*
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2007-11-10 05:39:37 +08:00
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* is kept at sysctl_sched_latency / sysctl_sched_min_granularity
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*/
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2007-11-27 04:21:49 +08:00
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static unsigned int sched_nr_latency = 5;
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2007-11-10 05:39:37 +08:00
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/*
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* After fork, child runs first. (default) If set to 0 then
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* parent will (try to) run first.
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2007-08-26 00:41:53 +08:00
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*/
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2007-11-10 05:39:37 +08:00
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const_debug unsigned int sysctl_sched_child_runs_first = 1;
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2007-07-10 00:51:58 +08:00
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2007-09-20 05:34:46 +08:00
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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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2007-07-10 00:51:58 +08:00
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/*
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* SCHED_OTHER wake-up granularity.
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2008-06-27 19:41:16 +08:00
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* (default: 5 msec * (1 + ilog(ncpus)), units: nanoseconds)
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2007-07-10 00:51:58 +08:00
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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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2008-06-27 19:41:16 +08:00
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unsigned int sysctl_sched_wakeup_granularity = 5000000UL;
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2007-07-10 00:51:58 +08:00
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2007-10-15 23:00:18 +08:00
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const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
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2008-10-18 01:27:03 +08:00
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static const struct sched_class fair_sched_class;
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2007-07-10 00:51:58 +08:00
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/**************************************************************
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* CFS operations on generic schedulable entities:
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*/
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2008-04-20 01:45:00 +08:00
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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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2007-10-15 23:00:03 +08:00
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#ifdef CONFIG_FAIR_GROUP_SCHED
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2007-07-10 00:51:58 +08:00
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2007-10-15 23:00:03 +08:00
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/* cpu runqueue to which this cfs_rq is attached */
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2007-07-10 00:51:58 +08:00
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
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{
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2007-10-15 23:00:03 +08:00
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return cfs_rq->rq;
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2007-07-10 00:51:58 +08:00
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}
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2007-10-15 23:00:03 +08:00
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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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2007-07-10 00:51:58 +08:00
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2008-04-20 01:45:00 +08:00
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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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2008-10-24 17:06:15 +08:00
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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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2007-10-15 23:00:03 +08:00
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#else /* CONFIG_FAIR_GROUP_SCHED */
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2007-07-10 00:51:58 +08:00
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2007-10-15 23:00:03 +08:00
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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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2007-07-10 00:51:58 +08:00
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}
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#define entity_is_task(se) 1
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2008-04-20 01:45:00 +08:00
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#define for_each_sched_entity(se) \
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for (; se; se = NULL)
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2007-07-10 00:51:58 +08:00
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2008-04-20 01:45:00 +08:00
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static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
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2007-07-10 00:51:58 +08:00
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{
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2008-04-20 01:45:00 +08:00
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return &task_rq(p)->cfs;
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2007-07-10 00:51:58 +08:00
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}
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2008-04-20 01:45:00 +08:00
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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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2008-10-24 17:06:15 +08:00
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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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2008-04-20 01:45:00 +08:00
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#endif /* CONFIG_FAIR_GROUP_SCHED */
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2007-07-10 00:51:58 +08:00
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/**************************************************************
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* Scheduling class tree data structure manipulation methods:
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*/
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2007-10-15 23:00:14 +08:00
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static inline u64 max_vruntime(u64 min_vruntime, u64 vruntime)
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2007-10-15 23:00:07 +08:00
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{
|
2007-10-15 23:00:11 +08:00
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s64 delta = (s64)(vruntime - min_vruntime);
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if (delta > 0)
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2007-10-15 23:00:07 +08:00
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min_vruntime = vruntime;
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return min_vruntime;
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}
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2007-10-15 23:00:14 +08:00
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static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
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2007-10-15 23:00:12 +08:00
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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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2007-10-15 23:00:14 +08:00
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static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
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2007-10-15 23:00:05 +08:00
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{
|
2007-10-15 23:00:07 +08:00
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return se->vruntime - cfs_rq->min_vruntime;
|
2007-10-15 23:00:05 +08:00
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}
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2008-10-24 17:06:13 +08:00
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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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|
sched: fix update_min_vruntime
Impact: fix SCHED_IDLE latency problems
OK, so we have 1 running task A (which is obviously curr and the tree is
equally obviously empty).
'A' nicely chugs along, doing its thing, carrying min_vruntime along as it
goes.
Then some whacko speed freak SCHED_IDLE task gets inserted due to SMP
balancing, which is very likely far right, in that case
update_curr
update_min_vruntime
cfs_rq->rb_leftmost := true (the crazy task sitting in a tree)
vruntime = se->vruntime
and voila, min_vruntime is waaay right of where it ought to be.
OK, so why did I write it like that to begin with...
Aah, yes.
Say we've just dequeued current
schedule
deactivate_task(prev)
dequeue_entity
update_min_vruntime
Then we'll set
vruntime = cfs_rq->min_vruntime;
we find !cfs_rq->curr, but do find someone in the tree. Then we _must_
do vruntime = se->vruntime, because
vruntime = min_vruntime(vruntime := cfs_rq->min_vruntime, se->vruntime)
will not advance vruntime, and cause lags the other way around (which we
fixed with that initial patch: 1af5f730fc1bf7c62ec9fb2d307206e18bf40a69
(sched: more accurate min_vruntime accounting).
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Mike Galbraith <efault@gmx.de>
Acked-by: Mike Galbraith <efault@gmx.de>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-15 21:53:39 +08:00
|
|
|
if (!cfs_rq->curr)
|
2008-10-24 17:06:13 +08:00
|
|
|
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);
|
|
|
|
}
|
|
|
|
|
2007-07-10 00:51:58 +08:00
|
|
|
/*
|
|
|
|
* Enqueue an entity into the rb-tree:
|
|
|
|
*/
|
2007-10-15 23:00:14 +08:00
|
|
|
static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
|
|
|
|
struct rb_node *parent = NULL;
|
|
|
|
struct sched_entity *entry;
|
2007-10-15 23:00:05 +08:00
|
|
|
s64 key = entity_key(cfs_rq, se);
|
2007-07-10 00:51:58 +08:00
|
|
|
int leftmost = 1;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Find the right place in the rbtree:
|
|
|
|
*/
|
|
|
|
while (*link) {
|
|
|
|
parent = *link;
|
|
|
|
entry = rb_entry(parent, struct sched_entity, run_node);
|
|
|
|
/*
|
|
|
|
* We dont care about collisions. Nodes with
|
|
|
|
* the same key stay together.
|
|
|
|
*/
|
2007-10-15 23:00:05 +08:00
|
|
|
if (key < entity_key(cfs_rq, entry)) {
|
2007-07-10 00:51:58 +08:00
|
|
|
link = &parent->rb_left;
|
|
|
|
} else {
|
|
|
|
link = &parent->rb_right;
|
|
|
|
leftmost = 0;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Maintain a cache of leftmost tree entries (it is frequently
|
|
|
|
* used):
|
|
|
|
*/
|
2008-10-24 17:06:13 +08:00
|
|
|
if (leftmost)
|
2007-10-15 23:00:11 +08:00
|
|
|
cfs_rq->rb_leftmost = &se->run_node;
|
2007-07-10 00:51:58 +08:00
|
|
|
|
|
|
|
rb_link_node(&se->run_node, parent, link);
|
|
|
|
rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
|
|
|
|
}
|
|
|
|
|
2007-10-15 23:00:14 +08:00
|
|
|
static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
2008-03-15 03:55:51 +08:00
|
|
|
if (cfs_rq->rb_leftmost == &se->run_node) {
|
|
|
|
struct rb_node *next_node;
|
|
|
|
|
|
|
|
next_node = rb_next(&se->run_node);
|
|
|
|
cfs_rq->rb_leftmost = next_node;
|
|
|
|
}
|
2007-10-15 23:00:04 +08:00
|
|
|
|
2007-07-10 00:51:58 +08:00
|
|
|
rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
|
|
|
|
}
|
|
|
|
|
|
|
|
static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
|
|
|
|
{
|
2008-11-05 04:25:07 +08:00
|
|
|
struct rb_node *left = cfs_rq->rb_leftmost;
|
|
|
|
|
|
|
|
if (!left)
|
|
|
|
return NULL;
|
|
|
|
|
|
|
|
return rb_entry(left, struct sched_entity, run_node);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
2008-11-05 04:25:07 +08:00
|
|
|
static struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
|
2007-10-15 23:00:05 +08:00
|
|
|
{
|
2008-02-22 17:32:21 +08:00
|
|
|
struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
|
2007-10-15 23:00:05 +08:00
|
|
|
|
2008-02-22 15:55:53 +08:00
|
|
|
if (!last)
|
|
|
|
return NULL;
|
2008-02-22 17:32:21 +08:00
|
|
|
|
|
|
|
return rb_entry(last, struct sched_entity, run_node);
|
2007-10-15 23:00:05 +08:00
|
|
|
}
|
|
|
|
|
2007-07-10 00:51:58 +08:00
|
|
|
/**************************************************************
|
|
|
|
* Scheduling class statistics methods:
|
|
|
|
*/
|
|
|
|
|
2007-11-10 05:39:37 +08:00
|
|
|
#ifdef CONFIG_SCHED_DEBUG
|
|
|
|
int sched_nr_latency_handler(struct ctl_table *table, int write,
|
|
|
|
struct file *filp, void __user *buffer, size_t *lenp,
|
|
|
|
loff_t *ppos)
|
|
|
|
{
|
|
|
|
int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
|
|
|
|
|
|
|
|
if (ret || !write)
|
|
|
|
return ret;
|
|
|
|
|
|
|
|
sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
|
|
|
|
sysctl_sched_min_granularity);
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
#endif
|
2007-10-15 23:00:13 +08:00
|
|
|
|
2008-06-27 19:41:11 +08:00
|
|
|
/*
|
2008-10-18 01:27:04 +08:00
|
|
|
* delta /= w
|
2008-06-27 19:41:11 +08:00
|
|
|
*/
|
|
|
|
static inline unsigned long
|
|
|
|
calc_delta_fair(unsigned long delta, struct sched_entity *se)
|
|
|
|
{
|
2008-10-18 01:27:04 +08:00
|
|
|
if (unlikely(se->load.weight != NICE_0_LOAD))
|
|
|
|
delta = calc_delta_mine(delta, NICE_0_LOAD, &se->load);
|
2008-06-27 19:41:11 +08:00
|
|
|
|
|
|
|
return delta;
|
|
|
|
}
|
|
|
|
|
2007-10-15 23:00:13 +08:00
|
|
|
/*
|
|
|
|
* The idea is to set a period in which each task runs once.
|
|
|
|
*
|
|
|
|
* When there are too many tasks (sysctl_sched_nr_latency) we have to stretch
|
|
|
|
* this period because otherwise the slices get too small.
|
|
|
|
*
|
|
|
|
* p = (nr <= nl) ? l : l*nr/nl
|
|
|
|
*/
|
2007-10-15 23:00:04 +08:00
|
|
|
static u64 __sched_period(unsigned long nr_running)
|
|
|
|
{
|
|
|
|
u64 period = sysctl_sched_latency;
|
2007-11-10 05:39:37 +08:00
|
|
|
unsigned long nr_latency = sched_nr_latency;
|
2007-10-15 23:00:04 +08:00
|
|
|
|
|
|
|
if (unlikely(nr_running > nr_latency)) {
|
2008-01-26 04:08:21 +08:00
|
|
|
period = sysctl_sched_min_granularity;
|
2007-10-15 23:00:04 +08:00
|
|
|
period *= nr_running;
|
|
|
|
}
|
|
|
|
|
|
|
|
return period;
|
|
|
|
}
|
|
|
|
|
2007-10-15 23:00:13 +08:00
|
|
|
/*
|
|
|
|
* We calculate the wall-time slice from the period by taking a part
|
|
|
|
* proportional to the weight.
|
|
|
|
*
|
2008-10-18 01:27:04 +08:00
|
|
|
* s = p*P[w/rw]
|
2007-10-15 23:00:13 +08:00
|
|
|
*/
|
2007-10-15 23:00:05 +08:00
|
|
|
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
2007-08-26 00:41:53 +08:00
|
|
|
{
|
2009-01-02 19:16:42 +08:00
|
|
|
u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
|
2008-10-18 01:27:04 +08:00
|
|
|
|
2009-01-02 19:16:42 +08:00
|
|
|
for_each_sched_entity(se) {
|
2009-01-16 00:17:15 +08:00
|
|
|
struct load_weight *load;
|
|
|
|
|
|
|
|
cfs_rq = cfs_rq_of(se);
|
|
|
|
load = &cfs_rq->load;
|
2008-10-18 01:27:04 +08:00
|
|
|
|
2009-01-02 19:16:42 +08:00
|
|
|
if (unlikely(!se->on_rq)) {
|
|
|
|
struct load_weight lw = cfs_rq->load;
|
|
|
|
|
|
|
|
update_load_add(&lw, se->load.weight);
|
|
|
|
load = &lw;
|
|
|
|
}
|
|
|
|
slice = calc_delta_mine(slice, se->load.weight, load);
|
|
|
|
}
|
|
|
|
return slice;
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
2007-10-15 23:00:13 +08:00
|
|
|
/*
|
2008-04-20 01:45:00 +08:00
|
|
|
* We calculate the vruntime slice of a to be inserted task
|
2007-10-15 23:00:13 +08:00
|
|
|
*
|
2008-10-18 01:27:04 +08:00
|
|
|
* vs = s/w
|
2007-10-15 23:00:13 +08:00
|
|
|
*/
|
2008-10-18 01:27:04 +08:00
|
|
|
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
2007-10-15 23:00:10 +08:00
|
|
|
{
|
2008-10-18 01:27:04 +08:00
|
|
|
return calc_delta_fair(sched_slice(cfs_rq, se), se);
|
2008-06-27 19:41:11 +08:00
|
|
|
}
|
|
|
|
|
2007-07-10 00:51:58 +08:00
|
|
|
/*
|
|
|
|
* Update the current task's runtime statistics. Skip current tasks that
|
|
|
|
* are not in our scheduling class.
|
|
|
|
*/
|
|
|
|
static inline void
|
2007-10-15 23:00:03 +08:00
|
|
|
__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
|
|
|
|
unsigned long delta_exec)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
2007-10-15 23:00:06 +08:00
|
|
|
unsigned long delta_exec_weighted;
|
2007-07-10 00:51:58 +08:00
|
|
|
|
2007-08-02 23:41:40 +08:00
|
|
|
schedstat_set(curr->exec_max, max((u64)delta_exec, curr->exec_max));
|
2007-07-10 00:51:58 +08:00
|
|
|
|
|
|
|
curr->sum_exec_runtime += delta_exec;
|
2007-10-15 23:00:06 +08:00
|
|
|
schedstat_add(cfs_rq, exec_clock, delta_exec);
|
2008-06-27 19:41:11 +08:00
|
|
|
delta_exec_weighted = calc_delta_fair(delta_exec, curr);
|
2007-10-15 23:00:04 +08:00
|
|
|
curr->vruntime += delta_exec_weighted;
|
2008-10-24 17:06:13 +08:00
|
|
|
update_min_vruntime(cfs_rq);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
2007-08-09 17:16:47 +08:00
|
|
|
static void update_curr(struct cfs_rq *cfs_rq)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
2007-10-15 23:00:03 +08:00
|
|
|
struct sched_entity *curr = cfs_rq->curr;
|
2007-10-15 23:00:03 +08:00
|
|
|
u64 now = rq_of(cfs_rq)->clock;
|
2007-07-10 00:51:58 +08:00
|
|
|
unsigned long delta_exec;
|
|
|
|
|
|
|
|
if (unlikely(!curr))
|
|
|
|
return;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Get the amount of time the current task was running
|
|
|
|
* since the last time we changed load (this cannot
|
|
|
|
* overflow on 32 bits):
|
|
|
|
*/
|
2007-10-15 23:00:03 +08:00
|
|
|
delta_exec = (unsigned long)(now - curr->exec_start);
|
2008-12-16 15:45:31 +08:00
|
|
|
if (!delta_exec)
|
|
|
|
return;
|
2007-07-10 00:51:58 +08:00
|
|
|
|
2007-10-15 23:00:03 +08:00
|
|
|
__update_curr(cfs_rq, curr, delta_exec);
|
|
|
|
curr->exec_start = now;
|
2007-12-03 03:04:49 +08:00
|
|
|
|
|
|
|
if (entity_is_task(curr)) {
|
|
|
|
struct task_struct *curtask = task_of(curr);
|
|
|
|
|
|
|
|
cpuacct_charge(curtask, delta_exec);
|
timers: fix itimer/many thread hang
Overview
This patch reworks the handling of POSIX CPU timers, including the
ITIMER_PROF, ITIMER_VIRT timers and rlimit handling. It was put together
with the help of Roland McGrath, the owner and original writer of this code.
The problem we ran into, and the reason for this rework, has to do with using
a profiling timer in a process with a large number of threads. It appears
that the performance of the old implementation of run_posix_cpu_timers() was
at least O(n*3) (where "n" is the number of threads in a process) or worse.
Everything is fine with an increasing number of threads until the time taken
for that routine to run becomes the same as or greater than the tick time, at
which point things degrade rather quickly.
This patch fixes bug 9906, "Weird hang with NPTL and SIGPROF."
Code Changes
This rework corrects the implementation of run_posix_cpu_timers() to make it
run in constant time for a particular machine. (Performance may vary between
one machine and another depending upon whether the kernel is built as single-
or multiprocessor and, in the latter case, depending upon the number of
running processors.) To do this, at each tick we now update fields in
signal_struct as well as task_struct. The run_posix_cpu_timers() function
uses those fields to make its decisions.
We define a new structure, "task_cputime," to contain user, system and
scheduler times and use these in appropriate places:
struct task_cputime {
cputime_t utime;
cputime_t stime;
unsigned long long sum_exec_runtime;
};
This is included in the structure "thread_group_cputime," which is a new
substructure of signal_struct and which varies for uniprocessor versus
multiprocessor kernels. For uniprocessor kernels, it uses "task_cputime" as
a simple substructure, while for multiprocessor kernels it is a pointer:
struct thread_group_cputime {
struct task_cputime totals;
};
struct thread_group_cputime {
struct task_cputime *totals;
};
We also add a new task_cputime substructure directly to signal_struct, to
cache the earliest expiration of process-wide timers, and task_cputime also
replaces the it_*_expires fields of task_struct (used for earliest expiration
of thread timers). The "thread_group_cputime" structure contains process-wide
timers that are updated via account_user_time() and friends. In the non-SMP
case the structure is a simple aggregator; unfortunately in the SMP case that
simplicity was not achievable due to cache-line contention between CPUs (in
one measured case performance was actually _worse_ on a 16-cpu system than
the same test on a 4-cpu system, due to this contention). For SMP, the
thread_group_cputime counters are maintained as a per-cpu structure allocated
using alloc_percpu(). The timer functions update only the timer field in
the structure corresponding to the running CPU, obtained using per_cpu_ptr().
We define a set of inline functions in sched.h that we use to maintain the
thread_group_cputime structure and hide the differences between UP and SMP
implementations from the rest of the kernel. The thread_group_cputime_init()
function initializes the thread_group_cputime structure for the given task.
The thread_group_cputime_alloc() is a no-op for UP; for SMP it calls the
out-of-line function thread_group_cputime_alloc_smp() to allocate and fill
in the per-cpu structures and fields. The thread_group_cputime_free()
function, also a no-op for UP, in SMP frees the per-cpu structures. The
thread_group_cputime_clone_thread() function (also a UP no-op) for SMP calls
thread_group_cputime_alloc() if the per-cpu structures haven't yet been
allocated. The thread_group_cputime() function fills the task_cputime
structure it is passed with the contents of the thread_group_cputime fields;
in UP it's that simple but in SMP it must also safely check that tsk->signal
is non-NULL (if it is it just uses the appropriate fields of task_struct) and,
if so, sums the per-cpu values for each online CPU. Finally, the three
functions account_group_user_time(), account_group_system_time() and
account_group_exec_runtime() are used by timer functions to update the
respective fields of the thread_group_cputime structure.
Non-SMP operation is trivial and will not be mentioned further.
The per-cpu structure is always allocated when a task creates its first new
thread, via a call to thread_group_cputime_clone_thread() from copy_signal().
It is freed at process exit via a call to thread_group_cputime_free() from
cleanup_signal().
All functions that formerly summed utime/stime/sum_sched_runtime values from
from all threads in the thread group now use thread_group_cputime() to
snapshot the values in the thread_group_cputime structure or the values in
the task structure itself if the per-cpu structure hasn't been allocated.
Finally, the code in kernel/posix-cpu-timers.c has changed quite a bit.
The run_posix_cpu_timers() function has been split into a fast path and a
slow path; the former safely checks whether there are any expired thread
timers and, if not, just returns, while the slow path does the heavy lifting.
With the dedicated thread group fields, timers are no longer "rebalanced" and
the process_timer_rebalance() function and related code has gone away. All
summing loops are gone and all code that used them now uses the
thread_group_cputime() inline. When process-wide timers are set, the new
task_cputime structure in signal_struct is used to cache the earliest
expiration; this is checked in the fast path.
Performance
The fix appears not to add significant overhead to existing operations. It
generally performs the same as the current code except in two cases, one in
which it performs slightly worse (Case 5 below) and one in which it performs
very significantly better (Case 2 below). Overall it's a wash except in those
two cases.
I've since done somewhat more involved testing on a dual-core Opteron system.
Case 1: With no itimer running, for a test with 100,000 threads, the fixed
kernel took 1428.5 seconds, 513 seconds more than the unfixed system,
all of which was spent in the system. There were twice as many
voluntary context switches with the fix as without it.
Case 2: With an itimer running at .01 second ticks and 4000 threads (the most
an unmodified kernel can handle), the fixed kernel ran the test in
eight percent of the time (5.8 seconds as opposed to 70 seconds) and
had better tick accuracy (.012 seconds per tick as opposed to .023
seconds per tick).
Case 3: A 4000-thread test with an initial timer tick of .01 second and an
interval of 10,000 seconds (i.e. a timer that ticks only once) had
very nearly the same performance in both cases: 6.3 seconds elapsed
for the fixed kernel versus 5.5 seconds for the unfixed kernel.
With fewer threads (eight in these tests), the Case 1 test ran in essentially
the same time on both the modified and unmodified kernels (5.2 seconds versus
5.8 seconds). The Case 2 test ran in about the same time as well, 5.9 seconds
versus 5.4 seconds but again with much better tick accuracy, .013 seconds per
tick versus .025 seconds per tick for the unmodified kernel.
Since the fix affected the rlimit code, I also tested soft and hard CPU limits.
Case 4: With a hard CPU limit of 20 seconds and eight threads (and an itimer
running), the modified kernel was very slightly favored in that while
it killed the process in 19.997 seconds of CPU time (5.002 seconds of
wall time), only .003 seconds of that was system time, the rest was
user time. The unmodified kernel killed the process in 20.001 seconds
of CPU (5.014 seconds of wall time) of which .016 seconds was system
time. Really, though, the results were too close to call. The results
were essentially the same with no itimer running.
Case 5: With a soft limit of 20 seconds and a hard limit of 2000 seconds
(where the hard limit would never be reached) and an itimer running,
the modified kernel exhibited worse tick accuracy than the unmodified
kernel: .050 seconds/tick versus .028 seconds/tick. Otherwise,
performance was almost indistinguishable. With no itimer running this
test exhibited virtually identical behavior and times in both cases.
In times past I did some limited performance testing. those results are below.
On a four-cpu Opteron system without this fix, a sixteen-thread test executed
in 3569.991 seconds, of which user was 3568.435s and system was 1.556s. On
the same system with the fix, user and elapsed time were about the same, but
system time dropped to 0.007 seconds. Performance with eight, four and one
thread were comparable. Interestingly, the timer ticks with the fix seemed
more accurate: The sixteen-thread test with the fix received 149543 ticks
for 0.024 seconds per tick, while the same test without the fix received 58720
for 0.061 seconds per tick. Both cases were configured for an interval of
0.01 seconds. Again, the other tests were comparable. Each thread in this
test computed the primes up to 25,000,000.
I also did a test with a large number of threads, 100,000 threads, which is
impossible without the fix. In this case each thread computed the primes only
up to 10,000 (to make the runtime manageable). System time dominated, at
1546.968 seconds out of a total 2176.906 seconds (giving a user time of
629.938s). It received 147651 ticks for 0.015 seconds per tick, still quite
accurate. There is obviously no comparable test without the fix.
Signed-off-by: Frank Mayhar <fmayhar@google.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-13 00:54:39 +08:00
|
|
|
account_group_exec_runtime(curtask, delta_exec);
|
2007-12-03 03:04:49 +08:00
|
|
|
}
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
static inline void
|
2007-08-09 17:16:47 +08:00
|
|
|
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
2007-08-09 17:16:47 +08:00
|
|
|
schedstat_set(se->wait_start, rq_of(cfs_rq)->clock);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Task is being enqueued - update stats:
|
|
|
|
*/
|
2007-08-09 17:16:47 +08:00
|
|
|
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
/*
|
|
|
|
* Are we enqueueing a waiting task? (for current tasks
|
|
|
|
* a dequeue/enqueue event is a NOP)
|
|
|
|
*/
|
2007-10-15 23:00:03 +08:00
|
|
|
if (se != cfs_rq->curr)
|
2007-08-09 17:16:47 +08:00
|
|
|
update_stats_wait_start(cfs_rq, se);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
static void
|
2007-08-09 17:16:47 +08:00
|
|
|
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
2007-10-15 23:00:06 +08:00
|
|
|
schedstat_set(se->wait_max, max(se->wait_max,
|
|
|
|
rq_of(cfs_rq)->clock - se->wait_start));
|
2008-01-26 04:08:35 +08:00
|
|
|
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);
|
2007-08-02 23:41:40 +08:00
|
|
|
schedstat_set(se->wait_start, 0);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
static inline void
|
2007-08-09 17:16:48 +08:00
|
|
|
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
/*
|
|
|
|
* Mark the end of the wait period if dequeueing a
|
|
|
|
* waiting task:
|
|
|
|
*/
|
2007-10-15 23:00:03 +08:00
|
|
|
if (se != cfs_rq->curr)
|
2007-08-09 17:16:47 +08:00
|
|
|
update_stats_wait_end(cfs_rq, se);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* We are picking a new current task - update its stats:
|
|
|
|
*/
|
|
|
|
static inline void
|
2007-08-09 17:16:47 +08:00
|
|
|
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
/*
|
|
|
|
* We are starting a new run period:
|
|
|
|
*/
|
2007-08-09 17:16:47 +08:00
|
|
|
se->exec_start = rq_of(cfs_rq)->clock;
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
/**************************************************
|
|
|
|
* Scheduling class queueing methods:
|
|
|
|
*/
|
|
|
|
|
2008-06-27 19:41:14 +08:00
|
|
|
#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
|
|
|
|
|
2007-10-15 23:00:07 +08:00
|
|
|
static void
|
|
|
|
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
|
|
{
|
|
|
|
update_load_add(&cfs_rq->load, se->load.weight);
|
2008-06-27 19:41:14 +08:00
|
|
|
if (!parent_entity(se))
|
|
|
|
inc_cpu_load(rq_of(cfs_rq), se->load.weight);
|
2008-09-25 12:23:54 +08:00
|
|
|
if (entity_is_task(se)) {
|
2008-06-27 19:41:14 +08:00
|
|
|
add_cfs_task_weight(cfs_rq, se->load.weight);
|
2008-09-25 12:23:54 +08:00
|
|
|
list_add(&se->group_node, &cfs_rq->tasks);
|
|
|
|
}
|
2007-10-15 23:00:07 +08:00
|
|
|
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);
|
2008-06-27 19:41:14 +08:00
|
|
|
if (!parent_entity(se))
|
|
|
|
dec_cpu_load(rq_of(cfs_rq), se->load.weight);
|
2008-09-25 12:23:54 +08:00
|
|
|
if (entity_is_task(se)) {
|
2008-06-27 19:41:14 +08:00
|
|
|
add_cfs_task_weight(cfs_rq, -se->load.weight);
|
2008-09-25 12:23:54 +08:00
|
|
|
list_del_init(&se->group_node);
|
|
|
|
}
|
2007-10-15 23:00:07 +08:00
|
|
|
cfs_rq->nr_running--;
|
|
|
|
se->on_rq = 0;
|
|
|
|
}
|
|
|
|
|
2007-08-09 17:16:48 +08:00
|
|
|
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
#ifdef CONFIG_SCHEDSTATS
|
|
|
|
if (se->sleep_start) {
|
2007-08-09 17:16:47 +08:00
|
|
|
u64 delta = rq_of(cfs_rq)->clock - se->sleep_start;
|
2008-01-26 04:08:34 +08:00
|
|
|
struct task_struct *tsk = task_of(se);
|
2007-07-10 00:51:58 +08:00
|
|
|
|
|
|
|
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;
|
2008-01-26 04:08:34 +08:00
|
|
|
|
|
|
|
account_scheduler_latency(tsk, delta >> 10, 1);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
if (se->block_start) {
|
2007-08-09 17:16:47 +08:00
|
|
|
u64 delta = rq_of(cfs_rq)->clock - se->block_start;
|
2008-01-26 04:08:34 +08:00
|
|
|
struct task_struct *tsk = task_of(se);
|
2007-07-10 00:51:58 +08:00
|
|
|
|
|
|
|
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;
|
2007-10-02 20:13:08 +08:00
|
|
|
|
|
|
|
/*
|
|
|
|
* 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)) {
|
2007-10-15 23:00:06 +08:00
|
|
|
|
2007-10-02 20:13:08 +08:00
|
|
|
profile_hits(SLEEP_PROFILING, (void *)get_wchan(tsk),
|
|
|
|
delta >> 20);
|
|
|
|
}
|
2008-01-26 04:08:34 +08:00
|
|
|
account_scheduler_latency(tsk, delta >> 10, 0);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
#endif
|
|
|
|
}
|
|
|
|
|
2007-10-15 23:00:10 +08:00
|
|
|
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
|
|
|
|
}
|
|
|
|
|
2007-10-15 23:00:05 +08:00
|
|
|
static void
|
|
|
|
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
|
|
|
|
{
|
2008-10-24 17:06:13 +08:00
|
|
|
u64 vruntime = cfs_rq->min_vruntime;
|
2007-10-15 23:00:05 +08:00
|
|
|
|
2007-11-10 05:39:37 +08:00
|
|
|
/*
|
|
|
|
* 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.
|
|
|
|
*/
|
2007-10-15 23:00:05 +08:00
|
|
|
if (initial && sched_feat(START_DEBIT))
|
2008-10-18 01:27:04 +08:00
|
|
|
vruntime += sched_vslice(cfs_rq, se);
|
2007-10-15 23:00:05 +08:00
|
|
|
|
2007-10-15 23:00:11 +08:00
|
|
|
if (!initial) {
|
2007-11-10 05:39:37 +08:00
|
|
|
/* sleeps upto a single latency don't count. */
|
2008-06-27 19:41:11 +08:00
|
|
|
if (sched_feat(NEW_FAIR_SLEEPERS)) {
|
|
|
|
unsigned long thresh = sysctl_sched_latency;
|
|
|
|
|
|
|
|
/*
|
2009-01-15 21:53:38 +08:00
|
|
|
* 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.
|
2008-06-27 19:41:11 +08:00
|
|
|
*/
|
2009-01-15 21:53:38 +08:00
|
|
|
if (sched_feat(NORMALIZED_SLEEPER) &&
|
|
|
|
task_of(se)->policy != SCHED_IDLE)
|
2008-06-27 19:41:11 +08:00
|
|
|
thresh = calc_delta_fair(thresh, se);
|
|
|
|
|
|
|
|
vruntime -= thresh;
|
|
|
|
}
|
2007-10-15 23:00:11 +08:00
|
|
|
|
2007-11-10 05:39:37 +08:00
|
|
|
/* ensure we never gain time by being placed backwards. */
|
|
|
|
vruntime = max_vruntime(se->vruntime, vruntime);
|
2007-10-15 23:00:05 +08:00
|
|
|
}
|
|
|
|
|
2007-10-15 23:00:10 +08:00
|
|
|
se->vruntime = vruntime;
|
2007-10-15 23:00:05 +08:00
|
|
|
}
|
|
|
|
|
2007-07-10 00:51:58 +08:00
|
|
|
static void
|
2007-10-15 23:00:08 +08:00
|
|
|
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
/*
|
2007-10-15 23:00:13 +08:00
|
|
|
* Update run-time statistics of the 'current'.
|
2007-07-10 00:51:58 +08:00
|
|
|
*/
|
2007-08-09 17:16:47 +08:00
|
|
|
update_curr(cfs_rq);
|
2008-05-06 05:56:17 +08:00
|
|
|
account_entity_enqueue(cfs_rq, se);
|
2007-07-10 00:51:58 +08:00
|
|
|
|
2007-10-15 23:00:04 +08:00
|
|
|
if (wakeup) {
|
2007-10-15 23:00:05 +08:00
|
|
|
place_entity(cfs_rq, se, 0);
|
2007-08-09 17:16:48 +08:00
|
|
|
enqueue_sleeper(cfs_rq, se);
|
2007-10-15 23:00:04 +08:00
|
|
|
}
|
2007-07-10 00:51:58 +08:00
|
|
|
|
2007-08-09 17:16:47 +08:00
|
|
|
update_stats_enqueue(cfs_rq, se);
|
2007-10-15 23:00:10 +08:00
|
|
|
check_spread(cfs_rq, se);
|
2007-10-15 23:00:08 +08:00
|
|
|
if (se != cfs_rq->curr)
|
|
|
|
__enqueue_entity(cfs_rq, se);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
2009-01-28 21:51:40 +08:00
|
|
|
static void __clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
2008-11-11 18:52:33 +08:00
|
|
|
{
|
|
|
|
if (cfs_rq->last == se)
|
|
|
|
cfs_rq->last = NULL;
|
|
|
|
|
|
|
|
if (cfs_rq->next == se)
|
|
|
|
cfs_rq->next = NULL;
|
|
|
|
}
|
|
|
|
|
2009-01-28 21:51:40 +08:00
|
|
|
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);
|
|
|
|
}
|
|
|
|
|
2007-07-10 00:51:58 +08:00
|
|
|
static void
|
2007-08-09 17:16:48 +08:00
|
|
|
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
2007-10-15 23:00:13 +08:00
|
|
|
/*
|
|
|
|
* Update run-time statistics of the 'current'.
|
|
|
|
*/
|
|
|
|
update_curr(cfs_rq);
|
|
|
|
|
2007-08-09 17:16:48 +08:00
|
|
|
update_stats_dequeue(cfs_rq, se);
|
2007-10-15 23:00:06 +08:00
|
|
|
if (sleep) {
|
2007-10-15 23:00:10 +08:00
|
|
|
#ifdef CONFIG_SCHEDSTATS
|
2007-07-10 00:51:58 +08:00
|
|
|
if (entity_is_task(se)) {
|
|
|
|
struct task_struct *tsk = task_of(se);
|
|
|
|
|
|
|
|
if (tsk->state & TASK_INTERRUPTIBLE)
|
2007-08-09 17:16:47 +08:00
|
|
|
se->sleep_start = rq_of(cfs_rq)->clock;
|
2007-07-10 00:51:58 +08:00
|
|
|
if (tsk->state & TASK_UNINTERRUPTIBLE)
|
2007-08-09 17:16:47 +08:00
|
|
|
se->block_start = rq_of(cfs_rq)->clock;
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
2007-10-15 23:00:06 +08:00
|
|
|
#endif
|
2007-10-15 23:00:10 +08:00
|
|
|
}
|
|
|
|
|
2008-11-11 18:52:33 +08:00
|
|
|
clear_buddies(cfs_rq, se);
|
sched: backward looking buddy
Impact: improve/change/fix wakeup-buddy scheduling
Currently we only have a forward looking buddy, that is, we prefer to
schedule to the task we last woke up, under the presumption that its
going to consume the data we just produced, and therefore will have
cache hot benefits.
This allows co-waking producer/consumer task pairs to run ahead of the
pack for a little while, keeping their cache warm. Without this, we
would interleave all pairs, utterly trashing the cache.
This patch introduces a backward looking buddy, that is, suppose that
in the above scenario, the consumer preempts the producer before it
can go to sleep, we will therefore miss the wakeup from consumer to
producer (its already running, after all), breaking the cycle and
reverting to the cache-trashing interleaved schedule pattern.
The backward buddy will try to schedule back to the task that woke us
up in case the forward buddy is not available, under the assumption
that the last task will be the one with the most cache hot task around
barring current.
This will basically allow a task to continue after it got preempted.
In order to avoid starvation, we allow either buddy to get wakeup_gran
ahead of the pack.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-05 04:25:09 +08:00
|
|
|
|
2007-10-15 23:00:08 +08:00
|
|
|
if (se != cfs_rq->curr)
|
2007-10-15 23:00:07 +08:00
|
|
|
__dequeue_entity(cfs_rq, se);
|
|
|
|
account_entity_dequeue(cfs_rq, se);
|
2008-10-24 17:06:13 +08:00
|
|
|
update_min_vruntime(cfs_rq);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Preempt the current task with a newly woken task if needed:
|
|
|
|
*/
|
2007-09-05 20:32:49 +08:00
|
|
|
static void
|
2007-10-15 23:00:05 +08:00
|
|
|
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
2007-09-05 20:32:49 +08:00
|
|
|
unsigned long ideal_runtime, delta_exec;
|
|
|
|
|
2007-10-15 23:00:05 +08:00
|
|
|
ideal_runtime = sched_slice(cfs_rq, curr);
|
2007-09-05 20:32:49 +08:00
|
|
|
delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
|
2009-01-28 21:51:39 +08:00
|
|
|
if (delta_exec > ideal_runtime) {
|
2007-07-10 00:51:58 +08:00
|
|
|
resched_task(rq_of(cfs_rq)->curr);
|
2009-01-28 21:51:39 +08:00
|
|
|
/*
|
|
|
|
* The current task ran long enough, ensure it doesn't get
|
|
|
|
* re-elected due to buddy favours.
|
|
|
|
*/
|
|
|
|
clear_buddies(cfs_rq, curr);
|
|
|
|
}
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
2007-10-15 23:00:08 +08:00
|
|
|
static void
|
2007-08-09 17:16:48 +08:00
|
|
|
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
2007-10-15 23:00:08 +08:00
|
|
|
/* '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);
|
|
|
|
}
|
|
|
|
|
2007-08-09 17:16:47 +08:00
|
|
|
update_stats_curr_start(cfs_rq, se);
|
2007-10-15 23:00:03 +08:00
|
|
|
cfs_rq->curr = se;
|
2007-10-15 23:00:02 +08:00
|
|
|
#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):
|
|
|
|
*/
|
2007-10-15 23:00:06 +08:00
|
|
|
if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
|
2007-10-15 23:00:02 +08:00
|
|
|
se->slice_max = max(se->slice_max,
|
|
|
|
se->sum_exec_runtime - se->prev_sum_exec_runtime);
|
|
|
|
}
|
|
|
|
#endif
|
2007-09-05 20:32:49 +08:00
|
|
|
se->prev_sum_exec_runtime = se->sum_exec_runtime;
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
2008-10-24 17:06:16 +08:00
|
|
|
static int
|
|
|
|
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
|
|
|
|
|
2008-11-05 04:25:07 +08:00
|
|
|
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
|
2008-03-15 04:12:12 +08:00
|
|
|
{
|
2008-11-05 04:25:07 +08:00
|
|
|
struct sched_entity *se = __pick_next_entity(cfs_rq);
|
|
|
|
|
sched: backward looking buddy
Impact: improve/change/fix wakeup-buddy scheduling
Currently we only have a forward looking buddy, that is, we prefer to
schedule to the task we last woke up, under the presumption that its
going to consume the data we just produced, and therefore will have
cache hot benefits.
This allows co-waking producer/consumer task pairs to run ahead of the
pack for a little while, keeping their cache warm. Without this, we
would interleave all pairs, utterly trashing the cache.
This patch introduces a backward looking buddy, that is, suppose that
in the above scenario, the consumer preempts the producer before it
can go to sleep, we will therefore miss the wakeup from consumer to
producer (its already running, after all), breaking the cycle and
reverting to the cache-trashing interleaved schedule pattern.
The backward buddy will try to schedule back to the task that woke us
up in case the forward buddy is not available, under the assumption
that the last task will be the one with the most cache hot task around
barring current.
This will basically allow a task to continue after it got preempted.
In order to avoid starvation, we allow either buddy to get wakeup_gran
ahead of the pack.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-05 04:25:09 +08:00
|
|
|
if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, se) < 1)
|
|
|
|
return cfs_rq->next;
|
2008-03-15 04:12:12 +08:00
|
|
|
|
sched: backward looking buddy
Impact: improve/change/fix wakeup-buddy scheduling
Currently we only have a forward looking buddy, that is, we prefer to
schedule to the task we last woke up, under the presumption that its
going to consume the data we just produced, and therefore will have
cache hot benefits.
This allows co-waking producer/consumer task pairs to run ahead of the
pack for a little while, keeping their cache warm. Without this, we
would interleave all pairs, utterly trashing the cache.
This patch introduces a backward looking buddy, that is, suppose that
in the above scenario, the consumer preempts the producer before it
can go to sleep, we will therefore miss the wakeup from consumer to
producer (its already running, after all), breaking the cycle and
reverting to the cache-trashing interleaved schedule pattern.
The backward buddy will try to schedule back to the task that woke us
up in case the forward buddy is not available, under the assumption
that the last task will be the one with the most cache hot task around
barring current.
This will basically allow a task to continue after it got preempted.
In order to avoid starvation, we allow either buddy to get wakeup_gran
ahead of the pack.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-05 04:25:09 +08:00
|
|
|
if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, se) < 1)
|
|
|
|
return cfs_rq->last;
|
|
|
|
|
|
|
|
return se;
|
2008-03-15 04:12:12 +08:00
|
|
|
}
|
|
|
|
|
2007-08-09 17:16:48 +08:00
|
|
|
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
/*
|
|
|
|
* If still on the runqueue then deactivate_task()
|
|
|
|
* was not called and update_curr() has to be done:
|
|
|
|
*/
|
|
|
|
if (prev->on_rq)
|
2007-08-09 17:16:47 +08:00
|
|
|
update_curr(cfs_rq);
|
2007-07-10 00:51:58 +08:00
|
|
|
|
2007-10-15 23:00:10 +08:00
|
|
|
check_spread(cfs_rq, prev);
|
2007-10-15 23:00:07 +08:00
|
|
|
if (prev->on_rq) {
|
2007-08-09 17:16:47 +08:00
|
|
|
update_stats_wait_start(cfs_rq, prev);
|
2007-10-15 23:00:07 +08:00
|
|
|
/* Put 'current' back into the tree. */
|
|
|
|
__enqueue_entity(cfs_rq, prev);
|
|
|
|
}
|
2007-10-15 23:00:03 +08:00
|
|
|
cfs_rq->curr = NULL;
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
2008-01-26 04:08:29 +08:00
|
|
|
static void
|
|
|
|
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
/*
|
2007-10-15 23:00:07 +08:00
|
|
|
* Update run-time statistics of the 'current'.
|
2007-07-10 00:51:58 +08:00
|
|
|
*/
|
2007-10-15 23:00:07 +08:00
|
|
|
update_curr(cfs_rq);
|
2007-07-10 00:51:58 +08:00
|
|
|
|
2008-01-26 04:08:29 +08:00
|
|
|
#ifdef CONFIG_SCHED_HRTICK
|
|
|
|
/*
|
|
|
|
* queued ticks are scheduled to match the slice, so don't bother
|
|
|
|
* validating it and just reschedule.
|
|
|
|
*/
|
2008-04-25 09:17:55 +08:00
|
|
|
if (queued) {
|
|
|
|
resched_task(rq_of(cfs_rq)->curr);
|
|
|
|
return;
|
|
|
|
}
|
2008-01-26 04:08:29 +08:00
|
|
|
/*
|
|
|
|
* 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
|
|
|
|
|
2007-10-15 23:00:14 +08:00
|
|
|
if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
|
2007-10-15 23:00:05 +08:00
|
|
|
check_preempt_tick(cfs_rq, curr);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
/**************************************************
|
|
|
|
* CFS operations on tasks:
|
|
|
|
*/
|
|
|
|
|
2008-01-26 04:08:29 +08:00
|
|
|
#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.
|
|
|
|
*/
|
2008-07-19 00:01:23 +08:00
|
|
|
if (rq->curr != p)
|
2008-07-28 17:53:11 +08:00
|
|
|
delta = max_t(s64, 10000LL, delta);
|
2008-01-26 04:08:29 +08:00
|
|
|
|
2008-07-19 00:01:23 +08:00
|
|
|
hrtick_start(rq, delta);
|
2008-01-26 04:08:29 +08:00
|
|
|
}
|
|
|
|
}
|
2008-10-18 01:27:03 +08:00
|
|
|
|
|
|
|
/*
|
|
|
|
* 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);
|
|
|
|
}
|
2008-06-25 02:09:43 +08:00
|
|
|
#else /* !CONFIG_SCHED_HRTICK */
|
2008-01-26 04:08:29 +08:00
|
|
|
static inline void
|
|
|
|
hrtick_start_fair(struct rq *rq, struct task_struct *p)
|
|
|
|
{
|
|
|
|
}
|
2008-10-18 01:27:03 +08:00
|
|
|
|
|
|
|
static inline void hrtick_update(struct rq *rq)
|
|
|
|
{
|
|
|
|
}
|
2008-01-26 04:08:29 +08:00
|
|
|
#endif
|
|
|
|
|
2007-07-10 00:51:58 +08:00
|
|
|
/*
|
|
|
|
* 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:
|
|
|
|
*/
|
2007-08-09 17:16:48 +08:00
|
|
|
static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
struct cfs_rq *cfs_rq;
|
2008-02-26 00:34:02 +08:00
|
|
|
struct sched_entity *se = &p->se;
|
2007-07-10 00:51:58 +08:00
|
|
|
|
|
|
|
for_each_sched_entity(se) {
|
2008-02-26 00:34:02 +08:00
|
|
|
if (se->on_rq)
|
2007-07-10 00:51:58 +08:00
|
|
|
break;
|
|
|
|
cfs_rq = cfs_rq_of(se);
|
2007-10-15 23:00:08 +08:00
|
|
|
enqueue_entity(cfs_rq, se, wakeup);
|
2007-10-15 23:00:12 +08:00
|
|
|
wakeup = 1;
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
2008-01-26 04:08:29 +08:00
|
|
|
|
2008-10-18 01:27:03 +08:00
|
|
|
hrtick_update(rq);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* The dequeue_task method is called before nr_running is
|
|
|
|
* decreased. We remove the task from the rbtree and
|
|
|
|
* update the fair scheduling stats:
|
|
|
|
*/
|
2007-08-09 17:16:48 +08:00
|
|
|
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
struct cfs_rq *cfs_rq;
|
2008-02-26 00:34:02 +08:00
|
|
|
struct sched_entity *se = &p->se;
|
2007-07-10 00:51:58 +08:00
|
|
|
|
|
|
|
for_each_sched_entity(se) {
|
|
|
|
cfs_rq = cfs_rq_of(se);
|
2007-08-09 17:16:48 +08:00
|
|
|
dequeue_entity(cfs_rq, se, sleep);
|
2007-07-10 00:51:58 +08:00
|
|
|
/* Don't dequeue parent if it has other entities besides us */
|
2008-02-26 00:34:02 +08:00
|
|
|
if (cfs_rq->load.weight)
|
2007-07-10 00:51:58 +08:00
|
|
|
break;
|
2007-10-15 23:00:12 +08:00
|
|
|
sleep = 1;
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
2008-01-26 04:08:29 +08:00
|
|
|
|
2008-10-18 01:27:03 +08:00
|
|
|
hrtick_update(rq);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
2007-09-20 05:34:46 +08:00
|
|
|
* 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.
|
2007-07-10 00:51:58 +08:00
|
|
|
*/
|
2007-10-15 23:00:08 +08:00
|
|
|
static void yield_task_fair(struct rq *rq)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
2007-12-05 00:04:39 +08:00
|
|
|
struct task_struct *curr = rq->curr;
|
|
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
|
|
|
|
struct sched_entity *rightmost, *se = &curr->se;
|
2007-07-10 00:51:58 +08:00
|
|
|
|
|
|
|
/*
|
2007-09-20 05:34:46 +08:00
|
|
|
* Are we the only task in the tree?
|
|
|
|
*/
|
|
|
|
if (unlikely(cfs_rq->nr_running == 1))
|
|
|
|
return;
|
|
|
|
|
2008-11-11 18:52:33 +08:00
|
|
|
clear_buddies(cfs_rq, se);
|
|
|
|
|
2007-12-05 00:04:39 +08:00
|
|
|
if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {
|
2008-05-04 00:29:28 +08:00
|
|
|
update_rq_clock(rq);
|
2007-09-20 05:34:46 +08:00
|
|
|
/*
|
2007-10-15 23:00:13 +08:00
|
|
|
* Update run-time statistics of the 'current'.
|
2007-09-20 05:34:46 +08:00
|
|
|
*/
|
2007-10-15 23:00:12 +08:00
|
|
|
update_curr(cfs_rq);
|
2007-09-20 05:34:46 +08:00
|
|
|
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
/*
|
|
|
|
* Find the rightmost entry in the rbtree:
|
2007-07-10 00:51:58 +08:00
|
|
|
*/
|
2007-10-15 23:00:12 +08:00
|
|
|
rightmost = __pick_last_entity(cfs_rq);
|
2007-09-20 05:34:46 +08:00
|
|
|
/*
|
|
|
|
* Already in the rightmost position?
|
|
|
|
*/
|
2008-02-18 20:39:37 +08:00
|
|
|
if (unlikely(!rightmost || rightmost->vruntime < se->vruntime))
|
2007-09-20 05:34:46 +08:00
|
|
|
return;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Minimally necessary key value to be last in the tree:
|
2007-10-15 23:00:12 +08:00
|
|
|
* Upon rescheduling, sched_class::put_prev_task() will place
|
|
|
|
* 'current' within the tree based on its new key value.
|
2007-09-20 05:34:46 +08:00
|
|
|
*/
|
2007-10-15 23:00:07 +08:00
|
|
|
se->vruntime = rightmost->vruntime + 1;
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
2008-01-26 04:08:09 +08:00
|
|
|
/*
|
|
|
|
* wake_idle() will wake a task on an idle cpu if task->cpu is
|
|
|
|
* not idle and an idle cpu is available. The span of cpus to
|
|
|
|
* search starts with cpus closest then further out as needed,
|
|
|
|
* so we always favor a closer, idle cpu.
|
2008-07-15 19:43:49 +08:00
|
|
|
* Domains may include CPUs that are not usable for migration,
|
2008-11-25 00:05:14 +08:00
|
|
|
* hence we need to mask them out (cpu_active_mask)
|
2008-01-26 04:08:09 +08:00
|
|
|
*
|
|
|
|
* Returns the CPU we should wake onto.
|
|
|
|
*/
|
|
|
|
#if defined(ARCH_HAS_SCHED_WAKE_IDLE)
|
|
|
|
static int wake_idle(int cpu, struct task_struct *p)
|
|
|
|
{
|
|
|
|
struct sched_domain *sd;
|
|
|
|
int i;
|
2008-12-19 01:56:29 +08:00
|
|
|
unsigned int chosen_wakeup_cpu;
|
|
|
|
int this_cpu;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* At POWERSAVINGS_BALANCE_WAKEUP level, if both this_cpu and prev_cpu
|
|
|
|
* are idle and this is not a kernel thread and this task's affinity
|
|
|
|
* allows it to be moved to preferred cpu, then just move!
|
|
|
|
*/
|
|
|
|
|
|
|
|
this_cpu = smp_processor_id();
|
|
|
|
chosen_wakeup_cpu =
|
|
|
|
cpu_rq(this_cpu)->rd->sched_mc_preferred_wakeup_cpu;
|
|
|
|
|
|
|
|
if (sched_mc_power_savings >= POWERSAVINGS_BALANCE_WAKEUP &&
|
|
|
|
idle_cpu(cpu) && idle_cpu(this_cpu) &&
|
|
|
|
p->mm && !(p->flags & PF_KTHREAD) &&
|
|
|
|
cpu_isset(chosen_wakeup_cpu, p->cpus_allowed))
|
|
|
|
return chosen_wakeup_cpu;
|
2008-01-26 04:08:09 +08:00
|
|
|
|
|
|
|
/*
|
|
|
|
* If it is idle, then it is the best cpu to run this task.
|
|
|
|
*
|
|
|
|
* This cpu is also the best, if it has more than one task already.
|
|
|
|
* Siblings must be also busy(in most cases) as they didn't already
|
|
|
|
* pickup the extra load from this cpu and hence we need not check
|
|
|
|
* sibling runqueue info. This will avoid the checks and cache miss
|
|
|
|
* penalities associated with that.
|
|
|
|
*/
|
2008-04-29 00:40:01 +08:00
|
|
|
if (idle_cpu(cpu) || cpu_rq(cpu)->cfs.nr_running > 1)
|
2008-01-26 04:08:09 +08:00
|
|
|
return cpu;
|
|
|
|
|
|
|
|
for_each_domain(cpu, sd) {
|
2008-04-15 13:04:23 +08:00
|
|
|
if ((sd->flags & SD_WAKE_IDLE)
|
|
|
|
|| ((sd->flags & SD_WAKE_IDLE_FAR)
|
|
|
|
&& !task_hot(p, task_rq(p)->clock, sd))) {
|
2008-11-25 00:05:04 +08:00
|
|
|
for_each_cpu_and(i, sched_domain_span(sd),
|
|
|
|
&p->cpus_allowed) {
|
|
|
|
if (cpu_active(i) && idle_cpu(i)) {
|
2008-01-26 04:08:09 +08:00
|
|
|
if (i != task_cpu(p)) {
|
|
|
|
schedstat_inc(p,
|
|
|
|
se.nr_wakeups_idle);
|
|
|
|
}
|
|
|
|
return i;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
} else {
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
return cpu;
|
|
|
|
}
|
2008-06-25 02:09:43 +08:00
|
|
|
#else /* !ARCH_HAS_SCHED_WAKE_IDLE*/
|
2008-01-26 04:08:09 +08:00
|
|
|
static inline int wake_idle(int cpu, struct task_struct *p)
|
|
|
|
{
|
|
|
|
return cpu;
|
|
|
|
}
|
|
|
|
#endif
|
|
|
|
|
|
|
|
#ifdef CONFIG_SMP
|
2008-03-17 03:36:10 +08:00
|
|
|
|
2008-06-27 19:41:27 +08:00
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
2008-06-27 19:41:39 +08:00
|
|
|
/*
|
|
|
|
* 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.
|
|
|
|
*
|
|
|
|
*/
|
2008-06-27 19:41:38 +08:00
|
|
|
static long effective_load(struct task_group *tg, int cpu,
|
|
|
|
long wl, long wg)
|
2008-06-27 19:41:27 +08:00
|
|
|
{
|
2008-06-27 19:41:30 +08:00
|
|
|
struct sched_entity *se = tg->se[cpu];
|
2008-06-27 19:41:38 +08:00
|
|
|
|
|
|
|
if (!tg->parent)
|
|
|
|
return wl;
|
|
|
|
|
2008-06-27 19:41:39 +08:00
|
|
|
/*
|
|
|
|
* 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;
|
|
|
|
|
2008-06-27 19:41:30 +08:00
|
|
|
for_each_sched_entity(se) {
|
2008-06-27 19:41:32 +08:00
|
|
|
long S, rw, s, a, b;
|
2008-09-23 21:33:42 +08:00
|
|
|
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;
|
2008-06-27 19:41:30 +08:00
|
|
|
|
|
|
|
S = se->my_q->tg->shares;
|
|
|
|
s = se->my_q->shares;
|
2008-06-27 19:41:38 +08:00
|
|
|
rw = se->my_q->rq_weight;
|
2008-06-27 19:41:27 +08:00
|
|
|
|
2008-06-27 19:41:32 +08:00
|
|
|
a = S*(rw + wl);
|
|
|
|
b = S*rw + s*wg;
|
2008-06-27 19:41:30 +08:00
|
|
|
|
2008-09-23 21:33:42 +08:00
|
|
|
wl = s*(a-b);
|
|
|
|
|
|
|
|
if (likely(b))
|
|
|
|
wl /= b;
|
|
|
|
|
sched: correct wakeup weight calculations
rw_i = {2, 4, 1, 0}
s_i = {2/7, 4/7, 1/7, 0}
wakeup on cpu0, weight=1
rw'_i = {3, 4, 1, 0}
s'_i = {3/8, 4/8, 1/8, 0}
s_0 = S * rw_0 / \Sum rw_j ->
\Sum rw_j = S*rw_0/s_0 = 1*2*7/2 = 7 (correct)
s'_0 = S * (rw_0 + 1) / (\Sum rw_j + 1) =
1 * (2+1) / (7+1) = 3/8 (correct
so we find that adding 1 to cpu0 gains 5/56 in weight
if say the other cpu were, cpu1, we'd also have to calculate its 4/56 loss
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-27 19:41:37 +08:00
|
|
|
/*
|
|
|
|
* 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.
|
|
|
|
*/
|
2008-06-27 19:41:30 +08:00
|
|
|
wg = 0;
|
|
|
|
}
|
2008-06-27 19:41:27 +08:00
|
|
|
|
2008-06-27 19:41:30 +08:00
|
|
|
return wl;
|
2008-06-27 19:41:27 +08:00
|
|
|
}
|
2008-06-27 19:41:30 +08:00
|
|
|
|
2008-06-27 19:41:27 +08:00
|
|
|
#else
|
2008-06-27 19:41:30 +08:00
|
|
|
|
sched: correct wakeup weight calculations
rw_i = {2, 4, 1, 0}
s_i = {2/7, 4/7, 1/7, 0}
wakeup on cpu0, weight=1
rw'_i = {3, 4, 1, 0}
s'_i = {3/8, 4/8, 1/8, 0}
s_0 = S * rw_0 / \Sum rw_j ->
\Sum rw_j = S*rw_0/s_0 = 1*2*7/2 = 7 (correct)
s'_0 = S * (rw_0 + 1) / (\Sum rw_j + 1) =
1 * (2+1) / (7+1) = 3/8 (correct
so we find that adding 1 to cpu0 gains 5/56 in weight
if say the other cpu were, cpu1, we'd also have to calculate its 4/56 loss
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-27 19:41:37 +08:00
|
|
|
static inline unsigned long effective_load(struct task_group *tg, int cpu,
|
|
|
|
unsigned long wl, unsigned long wg)
|
2008-06-27 19:41:30 +08:00
|
|
|
{
|
sched: correct wakeup weight calculations
rw_i = {2, 4, 1, 0}
s_i = {2/7, 4/7, 1/7, 0}
wakeup on cpu0, weight=1
rw'_i = {3, 4, 1, 0}
s'_i = {3/8, 4/8, 1/8, 0}
s_0 = S * rw_0 / \Sum rw_j ->
\Sum rw_j = S*rw_0/s_0 = 1*2*7/2 = 7 (correct)
s'_0 = S * (rw_0 + 1) / (\Sum rw_j + 1) =
1 * (2+1) / (7+1) = 3/8 (correct
so we find that adding 1 to cpu0 gains 5/56 in weight
if say the other cpu were, cpu1, we'd also have to calculate its 4/56 loss
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-27 19:41:37 +08:00
|
|
|
return wl;
|
2008-06-27 19:41:27 +08:00
|
|
|
}
|
2008-06-27 19:41:30 +08:00
|
|
|
|
2008-06-27 19:41:27 +08:00
|
|
|
#endif
|
|
|
|
|
2008-03-17 03:36:10 +08:00
|
|
|
static int
|
2008-09-30 19:45:39 +08:00
|
|
|
wake_affine(struct sched_domain *this_sd, struct rq *this_rq,
|
2008-03-19 08:42:00 +08:00
|
|
|
struct task_struct *p, int prev_cpu, int this_cpu, int sync,
|
|
|
|
int idx, unsigned long load, unsigned long this_load,
|
2008-03-17 03:36:10 +08:00
|
|
|
unsigned int imbalance)
|
|
|
|
{
|
|
|
|
unsigned long tl = this_load;
|
|
|
|
unsigned long tl_per_task;
|
2009-01-27 00:56:17 +08:00
|
|
|
struct task_group *tg;
|
sched: correct wakeup weight calculations
rw_i = {2, 4, 1, 0}
s_i = {2/7, 4/7, 1/7, 0}
wakeup on cpu0, weight=1
rw'_i = {3, 4, 1, 0}
s'_i = {3/8, 4/8, 1/8, 0}
s_0 = S * rw_0 / \Sum rw_j ->
\Sum rw_j = S*rw_0/s_0 = 1*2*7/2 = 7 (correct)
s'_0 = S * (rw_0 + 1) / (\Sum rw_j + 1) =
1 * (2+1) / (7+1) = 3/8 (correct
so we find that adding 1 to cpu0 gains 5/56 in weight
if say the other cpu were, cpu1, we'd also have to calculate its 4/56 loss
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-27 19:41:37 +08:00
|
|
|
unsigned long weight;
|
2008-05-29 17:11:41 +08:00
|
|
|
int balanced;
|
2008-03-17 03:36:10 +08:00
|
|
|
|
2008-05-29 17:11:41 +08:00
|
|
|
if (!(this_sd->flags & SD_WAKE_AFFINE) || !sched_feat(AFFINE_WAKEUPS))
|
2008-03-17 03:36:10 +08:00
|
|
|
return 0;
|
|
|
|
|
2008-05-29 17:11:41 +08:00
|
|
|
/*
|
|
|
|
* If sync wakeup then subtract the (maximum possible)
|
|
|
|
* effect of the currently running task from the load
|
|
|
|
* of the current CPU:
|
|
|
|
*/
|
sched: correct wakeup weight calculations
rw_i = {2, 4, 1, 0}
s_i = {2/7, 4/7, 1/7, 0}
wakeup on cpu0, weight=1
rw'_i = {3, 4, 1, 0}
s'_i = {3/8, 4/8, 1/8, 0}
s_0 = S * rw_0 / \Sum rw_j ->
\Sum rw_j = S*rw_0/s_0 = 1*2*7/2 = 7 (correct)
s'_0 = S * (rw_0 + 1) / (\Sum rw_j + 1) =
1 * (2+1) / (7+1) = 3/8 (correct
so we find that adding 1 to cpu0 gains 5/56 in weight
if say the other cpu were, cpu1, we'd also have to calculate its 4/56 loss
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-27 19:41:37 +08:00
|
|
|
if (sync) {
|
|
|
|
tg = task_group(current);
|
|
|
|
weight = current->se.load.weight;
|
|
|
|
|
|
|
|
tl += effective_load(tg, this_cpu, -weight, -weight);
|
|
|
|
load += effective_load(tg, prev_cpu, 0, -weight);
|
|
|
|
}
|
2008-05-29 17:11:41 +08:00
|
|
|
|
sched: correct wakeup weight calculations
rw_i = {2, 4, 1, 0}
s_i = {2/7, 4/7, 1/7, 0}
wakeup on cpu0, weight=1
rw'_i = {3, 4, 1, 0}
s'_i = {3/8, 4/8, 1/8, 0}
s_0 = S * rw_0 / \Sum rw_j ->
\Sum rw_j = S*rw_0/s_0 = 1*2*7/2 = 7 (correct)
s'_0 = S * (rw_0 + 1) / (\Sum rw_j + 1) =
1 * (2+1) / (7+1) = 3/8 (correct
so we find that adding 1 to cpu0 gains 5/56 in weight
if say the other cpu were, cpu1, we'd also have to calculate its 4/56 loss
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-27 19:41:37 +08:00
|
|
|
tg = task_group(p);
|
|
|
|
weight = p->se.load.weight;
|
2008-05-29 17:11:41 +08:00
|
|
|
|
sched: correct wakeup weight calculations
rw_i = {2, 4, 1, 0}
s_i = {2/7, 4/7, 1/7, 0}
wakeup on cpu0, weight=1
rw'_i = {3, 4, 1, 0}
s'_i = {3/8, 4/8, 1/8, 0}
s_0 = S * rw_0 / \Sum rw_j ->
\Sum rw_j = S*rw_0/s_0 = 1*2*7/2 = 7 (correct)
s'_0 = S * (rw_0 + 1) / (\Sum rw_j + 1) =
1 * (2+1) / (7+1) = 3/8 (correct
so we find that adding 1 to cpu0 gains 5/56 in weight
if say the other cpu were, cpu1, we'd also have to calculate its 4/56 loss
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-27 19:41:37 +08:00
|
|
|
balanced = 100*(tl + effective_load(tg, this_cpu, weight, weight)) <=
|
|
|
|
imbalance*(load + effective_load(tg, prev_cpu, 0, weight));
|
2008-05-29 17:11:41 +08:00
|
|
|
|
2008-03-17 03:36:10 +08:00
|
|
|
/*
|
2008-03-19 08:42:00 +08:00
|
|
|
* If the currently running task will sleep within
|
|
|
|
* a reasonable amount of time then attract this newly
|
|
|
|
* woken task:
|
2008-03-17 03:36:10 +08:00
|
|
|
*/
|
2008-10-08 15:16:04 +08:00
|
|
|
if (sync && balanced)
|
|
|
|
return 1;
|
2008-03-17 03:36:10 +08:00
|
|
|
|
|
|
|
schedstat_inc(p, se.nr_wakeups_affine_attempts);
|
|
|
|
tl_per_task = cpu_avg_load_per_task(this_cpu);
|
|
|
|
|
2008-09-30 19:45:39 +08:00
|
|
|
if (balanced || (tl <= load && tl + target_load(prev_cpu, idx) <=
|
|
|
|
tl_per_task)) {
|
2008-03-17 03:36:10 +08:00
|
|
|
/*
|
|
|
|
* This domain has SD_WAKE_AFFINE and
|
|
|
|
* p is cache cold in this domain, and
|
|
|
|
* there is no bad imbalance.
|
|
|
|
*/
|
|
|
|
schedstat_inc(this_sd, ttwu_move_affine);
|
|
|
|
schedstat_inc(p, se.nr_wakeups_affine);
|
|
|
|
|
|
|
|
return 1;
|
|
|
|
}
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2008-01-26 04:08:09 +08:00
|
|
|
static int select_task_rq_fair(struct task_struct *p, int sync)
|
|
|
|
{
|
|
|
|
struct sched_domain *sd, *this_sd = NULL;
|
2008-03-17 03:56:26 +08:00
|
|
|
int prev_cpu, this_cpu, new_cpu;
|
2008-03-17 03:36:10 +08:00
|
|
|
unsigned long load, this_load;
|
2008-09-30 19:45:39 +08:00
|
|
|
struct rq *this_rq;
|
2008-03-17 03:36:10 +08:00
|
|
|
unsigned int imbalance;
|
|
|
|
int idx;
|
2008-01-26 04:08:09 +08:00
|
|
|
|
2008-03-17 03:56:26 +08:00
|
|
|
prev_cpu = task_cpu(p);
|
|
|
|
this_cpu = smp_processor_id();
|
2008-03-19 08:42:00 +08:00
|
|
|
this_rq = cpu_rq(this_cpu);
|
2008-03-17 03:56:26 +08:00
|
|
|
new_cpu = prev_cpu;
|
2008-01-26 04:08:09 +08:00
|
|
|
|
2008-09-30 19:45:39 +08:00
|
|
|
if (prev_cpu == this_cpu)
|
|
|
|
goto out;
|
2008-03-17 03:56:26 +08:00
|
|
|
/*
|
|
|
|
* 'this_sd' is the first domain that both
|
|
|
|
* this_cpu and prev_cpu are present in:
|
|
|
|
*/
|
2008-01-26 04:08:09 +08:00
|
|
|
for_each_domain(this_cpu, sd) {
|
2008-11-25 00:05:04 +08:00
|
|
|
if (cpumask_test_cpu(prev_cpu, sched_domain_span(sd))) {
|
2008-01-26 04:08:09 +08:00
|
|
|
this_sd = sd;
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2008-11-25 00:05:14 +08:00
|
|
|
if (unlikely(!cpumask_test_cpu(this_cpu, &p->cpus_allowed)))
|
2008-03-17 04:21:47 +08:00
|
|
|
goto out;
|
2008-01-26 04:08:09 +08:00
|
|
|
|
|
|
|
/*
|
|
|
|
* Check for affine wakeup and passive balancing possibilities.
|
|
|
|
*/
|
2008-03-17 03:36:10 +08:00
|
|
|
if (!this_sd)
|
2008-03-17 04:21:47 +08:00
|
|
|
goto out;
|
2008-01-26 04:08:09 +08:00
|
|
|
|
2008-03-17 03:36:10 +08:00
|
|
|
idx = this_sd->wake_idx;
|
|
|
|
|
|
|
|
imbalance = 100 + (this_sd->imbalance_pct - 100) / 2;
|
|
|
|
|
2008-03-17 03:56:26 +08:00
|
|
|
load = source_load(prev_cpu, idx);
|
2008-03-17 03:36:10 +08:00
|
|
|
this_load = target_load(this_cpu, idx);
|
|
|
|
|
2008-09-30 19:45:39 +08:00
|
|
|
if (wake_affine(this_sd, this_rq, p, prev_cpu, this_cpu, sync, idx,
|
2008-03-19 08:42:00 +08:00
|
|
|
load, this_load, imbalance))
|
|
|
|
return this_cpu;
|
|
|
|
|
2008-03-17 03:36:10 +08:00
|
|
|
/*
|
|
|
|
* Start passive balancing when half the imbalance_pct
|
|
|
|
* limit is reached.
|
|
|
|
*/
|
|
|
|
if (this_sd->flags & SD_WAKE_BALANCE) {
|
|
|
|
if (imbalance*this_load <= 100*load) {
|
|
|
|
schedstat_inc(this_sd, ttwu_move_balance);
|
|
|
|
schedstat_inc(p, se.nr_wakeups_passive);
|
2008-03-19 08:42:00 +08:00
|
|
|
return this_cpu;
|
2008-01-26 04:08:09 +08:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2008-03-17 04:21:47 +08:00
|
|
|
out:
|
2008-01-26 04:08:09 +08:00
|
|
|
return wake_idle(new_cpu, p);
|
|
|
|
}
|
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
|
2008-04-20 01:44:57 +08:00
|
|
|
static unsigned long wakeup_gran(struct sched_entity *se)
|
|
|
|
{
|
|
|
|
unsigned long gran = sysctl_sched_wakeup_granularity;
|
|
|
|
|
|
|
|
/*
|
2008-06-27 19:41:11 +08:00
|
|
|
* More easily preempt - nice tasks, while not making it harder for
|
|
|
|
* + nice tasks.
|
2008-04-20 01:44:57 +08:00
|
|
|
*/
|
2008-10-24 17:06:15 +08:00
|
|
|
if (!sched_feat(ASYM_GRAN) || se->load.weight > NICE_0_LOAD)
|
|
|
|
gran = calc_delta_fair(sysctl_sched_wakeup_granularity, se);
|
2008-04-20 01:44:57 +08:00
|
|
|
|
|
|
|
return gran;
|
|
|
|
}
|
|
|
|
|
2008-10-24 17:06:15 +08:00
|
|
|
/*
|
|
|
|
* 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);
|
|
|
|
if (vdiff > gran)
|
|
|
|
return 1;
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2008-11-05 04:25:10 +08:00
|
|
|
static void set_last_buddy(struct sched_entity *se)
|
|
|
|
{
|
2009-01-15 21:53:38 +08:00
|
|
|
if (likely(task_of(se)->policy != SCHED_IDLE)) {
|
|
|
|
for_each_sched_entity(se)
|
|
|
|
cfs_rq_of(se)->last = se;
|
|
|
|
}
|
2008-11-05 04:25:10 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
static void set_next_buddy(struct sched_entity *se)
|
|
|
|
{
|
2009-01-15 21:53:38 +08:00
|
|
|
if (likely(task_of(se)->policy != SCHED_IDLE)) {
|
|
|
|
for_each_sched_entity(se)
|
|
|
|
cfs_rq_of(se)->next = se;
|
|
|
|
}
|
2008-11-05 04:25:10 +08:00
|
|
|
}
|
|
|
|
|
2007-07-10 00:51:58 +08:00
|
|
|
/*
|
|
|
|
* Preempt the current task with a newly woken task if needed:
|
|
|
|
*/
|
2008-09-21 05:38:02 +08:00
|
|
|
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
struct task_struct *curr = rq->curr;
|
2007-10-15 23:00:12 +08:00
|
|
|
struct sched_entity *se = &curr->se, *pse = &p->se;
|
2008-12-16 15:45:30 +08:00
|
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
|
2007-07-10 00:51:58 +08:00
|
|
|
|
2008-12-16 15:45:30 +08:00
|
|
|
update_curr(cfs_rq);
|
sched: backward looking buddy
Impact: improve/change/fix wakeup-buddy scheduling
Currently we only have a forward looking buddy, that is, we prefer to
schedule to the task we last woke up, under the presumption that its
going to consume the data we just produced, and therefore will have
cache hot benefits.
This allows co-waking producer/consumer task pairs to run ahead of the
pack for a little while, keeping their cache warm. Without this, we
would interleave all pairs, utterly trashing the cache.
This patch introduces a backward looking buddy, that is, suppose that
in the above scenario, the consumer preempts the producer before it
can go to sleep, we will therefore miss the wakeup from consumer to
producer (its already running, after all), breaking the cycle and
reverting to the cache-trashing interleaved schedule pattern.
The backward buddy will try to schedule back to the task that woke us
up in case the forward buddy is not available, under the assumption
that the last task will be the one with the most cache hot task around
barring current.
This will basically allow a task to continue after it got preempted.
In order to avoid starvation, we allow either buddy to get wakeup_gran
ahead of the pack.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-05 04:25:09 +08:00
|
|
|
|
2008-12-16 15:45:30 +08:00
|
|
|
if (unlikely(rt_prio(p->prio))) {
|
2007-07-10 00:51:58 +08:00
|
|
|
resched_task(curr);
|
|
|
|
return;
|
|
|
|
}
|
2008-03-15 04:12:12 +08:00
|
|
|
|
2008-11-05 04:25:08 +08:00
|
|
|
if (unlikely(p->sched_class != &fair_sched_class))
|
|
|
|
return;
|
|
|
|
|
2008-03-19 08:42:00 +08:00
|
|
|
if (unlikely(se == pse))
|
|
|
|
return;
|
|
|
|
|
sched: backward looking buddy
Impact: improve/change/fix wakeup-buddy scheduling
Currently we only have a forward looking buddy, that is, we prefer to
schedule to the task we last woke up, under the presumption that its
going to consume the data we just produced, and therefore will have
cache hot benefits.
This allows co-waking producer/consumer task pairs to run ahead of the
pack for a little while, keeping their cache warm. Without this, we
would interleave all pairs, utterly trashing the cache.
This patch introduces a backward looking buddy, that is, suppose that
in the above scenario, the consumer preempts the producer before it
can go to sleep, we will therefore miss the wakeup from consumer to
producer (its already running, after all), breaking the cycle and
reverting to the cache-trashing interleaved schedule pattern.
The backward buddy will try to schedule back to the task that woke us
up in case the forward buddy is not available, under the assumption
that the last task will be the one with the most cache hot task around
barring current.
This will basically allow a task to continue after it got preempted.
In order to avoid starvation, we allow either buddy to get wakeup_gran
ahead of the pack.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-05 04:25:09 +08:00
|
|
|
/*
|
|
|
|
* 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 the idle thread.
|
|
|
|
*/
|
|
|
|
if (sched_feat(LAST_BUDDY) && likely(se->on_rq && curr != rq->idle))
|
2008-11-05 04:25:10 +08:00
|
|
|
set_last_buddy(se);
|
|
|
|
set_next_buddy(pse);
|
2008-09-23 21:33:45 +08:00
|
|
|
|
2008-08-28 17:12:49 +08:00
|
|
|
/*
|
|
|
|
* We can come here with TIF_NEED_RESCHED already set from new task
|
|
|
|
* wake up path.
|
|
|
|
*/
|
|
|
|
if (test_tsk_need_resched(curr))
|
|
|
|
return;
|
|
|
|
|
2007-10-15 23:00:18 +08:00
|
|
|
/*
|
2009-01-15 21:53:38 +08:00
|
|
|
* Batch and idle tasks do not preempt (their preemption is driven by
|
2007-10-15 23:00:18 +08:00
|
|
|
* the tick):
|
|
|
|
*/
|
2009-01-15 21:53:38 +08:00
|
|
|
if (unlikely(p->policy != SCHED_NORMAL))
|
2007-10-15 23:00:18 +08:00
|
|
|
return;
|
2007-07-10 00:51:58 +08:00
|
|
|
|
2009-01-15 21:53:38 +08:00
|
|
|
/* Idle tasks are by definition preempted by everybody. */
|
|
|
|
if (unlikely(curr->policy == SCHED_IDLE)) {
|
|
|
|
resched_task(curr);
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
2007-11-10 05:39:39 +08:00
|
|
|
if (!sched_feat(WAKEUP_PREEMPT))
|
|
|
|
return;
|
2007-10-15 23:00:12 +08:00
|
|
|
|
2009-01-27 00:56:17 +08:00
|
|
|
if (sched_feat(WAKEUP_OVERLAP) && sync) {
|
2008-09-21 05:38:02 +08:00
|
|
|
resched_task(curr);
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
2008-10-24 17:06:15 +08:00
|
|
|
find_matching_se(&se, &pse);
|
|
|
|
|
|
|
|
while (se) {
|
|
|
|
BUG_ON(!pse);
|
|
|
|
|
|
|
|
if (wakeup_preempt_entity(se, pse) == 1) {
|
|
|
|
resched_task(curr);
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
|
|
|
|
se = parent_entity(se);
|
|
|
|
pse = parent_entity(pse);
|
|
|
|
}
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
2007-08-09 17:16:48 +08:00
|
|
|
static struct task_struct *pick_next_task_fair(struct rq *rq)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
2008-01-26 04:08:29 +08:00
|
|
|
struct task_struct *p;
|
2007-07-10 00:51:58 +08:00
|
|
|
struct cfs_rq *cfs_rq = &rq->cfs;
|
|
|
|
struct sched_entity *se;
|
|
|
|
|
|
|
|
if (unlikely(!cfs_rq->nr_running))
|
|
|
|
return NULL;
|
|
|
|
|
|
|
|
do {
|
2007-08-09 17:16:48 +08:00
|
|
|
se = pick_next_entity(cfs_rq);
|
2009-01-28 21:51:39 +08:00
|
|
|
/*
|
|
|
|
* If se was a buddy, clear it so that it will have to earn
|
|
|
|
* the favour again.
|
|
|
|
*/
|
2009-01-28 21:51:40 +08:00
|
|
|
__clear_buddies(cfs_rq, se);
|
2008-11-05 04:25:07 +08:00
|
|
|
set_next_entity(cfs_rq, se);
|
2007-07-10 00:51:58 +08:00
|
|
|
cfs_rq = group_cfs_rq(se);
|
|
|
|
} while (cfs_rq);
|
|
|
|
|
2008-01-26 04:08:29 +08:00
|
|
|
p = task_of(se);
|
|
|
|
hrtick_start_fair(rq, p);
|
|
|
|
|
|
|
|
return p;
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Account for a descheduled task:
|
|
|
|
*/
|
2007-08-09 17:16:49 +08:00
|
|
|
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
struct sched_entity *se = &prev->se;
|
|
|
|
struct cfs_rq *cfs_rq;
|
|
|
|
|
|
|
|
for_each_sched_entity(se) {
|
|
|
|
cfs_rq = cfs_rq_of(se);
|
2007-08-09 17:16:48 +08:00
|
|
|
put_prev_entity(cfs_rq, se);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2007-10-25 00:23:51 +08:00
|
|
|
#ifdef CONFIG_SMP
|
2007-07-10 00:51:58 +08:00
|
|
|
/**************************************************
|
|
|
|
* Fair scheduling class load-balancing methods:
|
|
|
|
*/
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Load-balancing iterator. Note: while the runqueue stays locked
|
|
|
|
* during the whole iteration, the current task might be
|
|
|
|
* dequeued so the iterator has to be dequeue-safe. Here we
|
|
|
|
* achieve that by always pre-iterating before returning
|
|
|
|
* the current task:
|
|
|
|
*/
|
2007-10-15 23:00:13 +08:00
|
|
|
static struct task_struct *
|
2008-04-20 01:45:00 +08:00
|
|
|
__load_balance_iterator(struct cfs_rq *cfs_rq, struct list_head *next)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
2008-04-20 01:44:59 +08:00
|
|
|
struct task_struct *p = NULL;
|
|
|
|
struct sched_entity *se;
|
2007-07-10 00:51:58 +08:00
|
|
|
|
2008-08-11 19:32:02 +08:00
|
|
|
if (next == &cfs_rq->tasks)
|
|
|
|
return NULL;
|
|
|
|
|
2008-09-25 12:23:54 +08:00
|
|
|
se = list_entry(next, struct sched_entity, group_node);
|
|
|
|
p = task_of(se);
|
|
|
|
cfs_rq->balance_iterator = next->next;
|
2008-08-11 19:32:02 +08:00
|
|
|
|
2007-07-10 00:51:58 +08:00
|
|
|
return p;
|
|
|
|
}
|
|
|
|
|
|
|
|
static struct task_struct *load_balance_start_fair(void *arg)
|
|
|
|
{
|
|
|
|
struct cfs_rq *cfs_rq = arg;
|
|
|
|
|
2008-04-20 01:45:00 +08:00
|
|
|
return __load_balance_iterator(cfs_rq, cfs_rq->tasks.next);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
static struct task_struct *load_balance_next_fair(void *arg)
|
|
|
|
{
|
|
|
|
struct cfs_rq *cfs_rq = arg;
|
|
|
|
|
2008-04-20 01:45:00 +08:00
|
|
|
return __load_balance_iterator(cfs_rq, cfs_rq->balance_iterator);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
2008-06-27 19:41:14 +08:00
|
|
|
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,
|
|
|
|
struct cfs_rq *cfs_rq)
|
2008-02-26 00:34:02 +08:00
|
|
|
{
|
2008-06-27 19:41:14 +08:00
|
|
|
struct rq_iterator cfs_rq_iterator;
|
2008-02-26 00:34:02 +08:00
|
|
|
|
2008-06-27 19:41:14 +08:00
|
|
|
cfs_rq_iterator.start = load_balance_start_fair;
|
|
|
|
cfs_rq_iterator.next = load_balance_next_fair;
|
|
|
|
cfs_rq_iterator.arg = cfs_rq;
|
2008-02-26 00:34:02 +08:00
|
|
|
|
2008-06-27 19:41:14 +08:00
|
|
|
return balance_tasks(this_rq, this_cpu, busiest,
|
|
|
|
max_load_move, sd, idle, all_pinned,
|
|
|
|
this_best_prio, &cfs_rq_iterator);
|
2008-02-26 00:34:02 +08:00
|
|
|
}
|
|
|
|
|
2008-06-27 19:41:14 +08:00
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
sched: simplify move_tasks()
The move_tasks() function is currently multiplexed with two distinct
capabilities:
1. attempt to move a specified amount of weighted load from one run
queue to another; and
2. attempt to move a specified number of tasks from one run queue to
another.
The first of these capabilities is used in two places, load_balance()
and load_balance_idle(), and in both of these cases the return value of
move_tasks() is used purely to decide if tasks/load were moved and no
notice of the actual number of tasks moved is taken.
The second capability is used in exactly one place,
active_load_balance(), to attempt to move exactly one task and, as
before, the return value is only used as an indicator of success or failure.
This multiplexing of sched_task() was introduced, by me, as part of the
smpnice patches and was motivated by the fact that the alternative, one
function to move specified load and one to move a single task, would
have led to two functions of roughly the same complexity as the old
move_tasks() (or the new balance_tasks()). However, the new modular
design of the new CFS scheduler allows a simpler solution to be adopted
and this patch addresses that solution by:
1. adding a new function, move_one_task(), to be used by
active_load_balance(); and
2. making move_tasks() a single purpose function that tries to move a
specified weighted load and returns 1 for success and 0 for failure.
One of the consequences of these changes is that neither move_one_task()
or the new move_tasks() care how many tasks sched_class.load_balance()
moves and this enables its interface to be simplified by returning the
amount of load moved as its result and removing the load_moved pointer
from the argument list. This helps simplify the new move_tasks() and
slightly reduces the amount of work done in each of
sched_class.load_balance()'s implementations.
Further simplification, e.g. changes to balance_tasks(), are possible
but (slightly) complicated by the special needs of load_balance_fair()
so I've left them to a later patch (if this one gets accepted).
NB Since move_tasks() gets called with two run queue locks held even
small reductions in overhead are worthwhile.
[ mingo@elte.hu ]
this change also reduces code size nicely:
text data bss dec hex filename
39216 3618 24 42858 a76a sched.o.before
39173 3618 24 42815 a73f sched.o.after
Signed-off-by: Peter Williams <pwil3058@bigpond.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2007-08-09 17:16:46 +08:00
|
|
|
static unsigned long
|
2007-07-10 00:51:58 +08:00
|
|
|
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
2007-10-25 00:23:51 +08:00
|
|
|
unsigned long max_load_move,
|
2007-08-09 17:16:46 +08:00
|
|
|
struct sched_domain *sd, enum cpu_idle_type idle,
|
|
|
|
int *all_pinned, int *this_best_prio)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
long rem_load_move = max_load_move;
|
2008-06-27 19:41:14 +08:00
|
|
|
int busiest_cpu = cpu_of(busiest);
|
|
|
|
struct task_group *tg;
|
2008-04-20 01:45:00 +08:00
|
|
|
|
2008-06-27 19:41:14 +08:00
|
|
|
rcu_read_lock();
|
2008-06-27 19:41:23 +08:00
|
|
|
update_h_load(busiest_cpu);
|
2008-04-20 01:45:00 +08:00
|
|
|
|
2008-09-23 01:06:09 +08:00
|
|
|
list_for_each_entry_rcu(tg, &task_groups, list) {
|
2008-06-27 19:41:23 +08:00
|
|
|
struct cfs_rq *busiest_cfs_rq = tg->cfs_rq[busiest_cpu];
|
2008-06-27 19:41:29 +08:00
|
|
|
unsigned long busiest_h_load = busiest_cfs_rq->h_load;
|
|
|
|
unsigned long busiest_weight = busiest_cfs_rq->load.weight;
|
2008-06-27 19:41:36 +08:00
|
|
|
u64 rem_load, moved_load;
|
2008-04-20 01:45:00 +08:00
|
|
|
|
2008-06-27 19:41:14 +08:00
|
|
|
/*
|
|
|
|
* empty group
|
|
|
|
*/
|
2008-06-27 19:41:23 +08:00
|
|
|
if (!busiest_cfs_rq->task_weight)
|
2007-07-10 00:51:58 +08:00
|
|
|
continue;
|
|
|
|
|
2008-06-27 19:41:36 +08:00
|
|
|
rem_load = (u64)rem_load_move * busiest_weight;
|
|
|
|
rem_load = div_u64(rem_load, busiest_h_load + 1);
|
2007-07-10 00:51:58 +08:00
|
|
|
|
2008-06-27 19:41:14 +08:00
|
|
|
moved_load = __load_balance_fair(this_rq, this_cpu, busiest,
|
2008-06-27 19:41:20 +08:00
|
|
|
rem_load, sd, idle, all_pinned, this_best_prio,
|
2008-06-27 19:41:14 +08:00
|
|
|
tg->cfs_rq[busiest_cpu]);
|
2007-07-10 00:51:58 +08:00
|
|
|
|
2008-06-27 19:41:14 +08:00
|
|
|
if (!moved_load)
|
2007-07-10 00:51:58 +08:00
|
|
|
continue;
|
|
|
|
|
2008-06-27 19:41:29 +08:00
|
|
|
moved_load *= busiest_h_load;
|
2008-06-27 19:41:36 +08:00
|
|
|
moved_load = div_u64(moved_load, busiest_weight + 1);
|
2007-07-10 00:51:58 +08:00
|
|
|
|
2008-06-27 19:41:14 +08:00
|
|
|
rem_load_move -= moved_load;
|
|
|
|
if (rem_load_move < 0)
|
2007-07-10 00:51:58 +08:00
|
|
|
break;
|
|
|
|
}
|
2008-06-27 19:41:14 +08:00
|
|
|
rcu_read_unlock();
|
2007-07-10 00:51:58 +08:00
|
|
|
|
sched: simplify move_tasks()
The move_tasks() function is currently multiplexed with two distinct
capabilities:
1. attempt to move a specified amount of weighted load from one run
queue to another; and
2. attempt to move a specified number of tasks from one run queue to
another.
The first of these capabilities is used in two places, load_balance()
and load_balance_idle(), and in both of these cases the return value of
move_tasks() is used purely to decide if tasks/load were moved and no
notice of the actual number of tasks moved is taken.
The second capability is used in exactly one place,
active_load_balance(), to attempt to move exactly one task and, as
before, the return value is only used as an indicator of success or failure.
This multiplexing of sched_task() was introduced, by me, as part of the
smpnice patches and was motivated by the fact that the alternative, one
function to move specified load and one to move a single task, would
have led to two functions of roughly the same complexity as the old
move_tasks() (or the new balance_tasks()). However, the new modular
design of the new CFS scheduler allows a simpler solution to be adopted
and this patch addresses that solution by:
1. adding a new function, move_one_task(), to be used by
active_load_balance(); and
2. making move_tasks() a single purpose function that tries to move a
specified weighted load and returns 1 for success and 0 for failure.
One of the consequences of these changes is that neither move_one_task()
or the new move_tasks() care how many tasks sched_class.load_balance()
moves and this enables its interface to be simplified by returning the
amount of load moved as its result and removing the load_moved pointer
from the argument list. This helps simplify the new move_tasks() and
slightly reduces the amount of work done in each of
sched_class.load_balance()'s implementations.
Further simplification, e.g. changes to balance_tasks(), are possible
but (slightly) complicated by the special needs of load_balance_fair()
so I've left them to a later patch (if this one gets accepted).
NB Since move_tasks() gets called with two run queue locks held even
small reductions in overhead are worthwhile.
[ mingo@elte.hu ]
this change also reduces code size nicely:
text data bss dec hex filename
39216 3618 24 42858 a76a sched.o.before
39173 3618 24 42815 a73f sched.o.after
Signed-off-by: Peter Williams <pwil3058@bigpond.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2007-08-09 17:16:46 +08:00
|
|
|
return max_load_move - rem_load_move;
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
2008-06-27 19:41:14 +08:00
|
|
|
#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 __load_balance_fair(this_rq, this_cpu, busiest,
|
|
|
|
max_load_move, sd, idle, all_pinned,
|
|
|
|
this_best_prio, &busiest->cfs);
|
|
|
|
}
|
|
|
|
#endif
|
2007-07-10 00:51:58 +08:00
|
|
|
|
2007-10-25 00:23:51 +08:00
|
|
|
static int
|
|
|
|
move_one_task_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
|
|
|
struct sched_domain *sd, enum cpu_idle_type idle)
|
|
|
|
{
|
|
|
|
struct cfs_rq *busy_cfs_rq;
|
|
|
|
struct rq_iterator cfs_rq_iterator;
|
|
|
|
|
|
|
|
cfs_rq_iterator.start = load_balance_start_fair;
|
|
|
|
cfs_rq_iterator.next = load_balance_next_fair;
|
|
|
|
|
|
|
|
for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
|
|
|
|
/*
|
|
|
|
* pass busy_cfs_rq argument into
|
|
|
|
* load_balance_[start|next]_fair iterators
|
|
|
|
*/
|
|
|
|
cfs_rq_iterator.arg = busy_cfs_rq;
|
|
|
|
if (iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
|
|
|
|
&cfs_rq_iterator))
|
|
|
|
return 1;
|
|
|
|
}
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
2008-06-25 02:09:43 +08:00
|
|
|
#endif /* CONFIG_SMP */
|
2007-10-25 00:23:51 +08:00
|
|
|
|
2007-07-10 00:51:58 +08:00
|
|
|
/*
|
|
|
|
* scheduler tick hitting a task of our scheduling class:
|
|
|
|
*/
|
2008-01-26 04:08:29 +08:00
|
|
|
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
struct cfs_rq *cfs_rq;
|
|
|
|
struct sched_entity *se = &curr->se;
|
|
|
|
|
|
|
|
for_each_sched_entity(se) {
|
|
|
|
cfs_rq = cfs_rq_of(se);
|
2008-01-26 04:08:29 +08:00
|
|
|
entity_tick(cfs_rq, se, queued);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Share the fairness runtime between parent and child, thus the
|
|
|
|
* total amount of pressure for CPU stays equal - new tasks
|
|
|
|
* get a chance to run but frequent forkers are not allowed to
|
|
|
|
* monopolize the CPU. Note: the parent runqueue is locked,
|
|
|
|
* the child is not running yet.
|
|
|
|
*/
|
2007-08-09 17:16:49 +08:00
|
|
|
static void task_new_fair(struct rq *rq, struct task_struct *p)
|
2007-07-10 00:51:58 +08:00
|
|
|
{
|
|
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(p);
|
2007-10-15 23:00:03 +08:00
|
|
|
struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
|
2007-10-15 23:00:14 +08:00
|
|
|
int this_cpu = smp_processor_id();
|
2007-07-10 00:51:58 +08:00
|
|
|
|
|
|
|
sched_info_queued(p);
|
|
|
|
|
2007-08-28 18:53:24 +08:00
|
|
|
update_curr(cfs_rq);
|
2007-10-15 23:00:05 +08:00
|
|
|
place_entity(cfs_rq, se, 1);
|
2007-10-15 23:00:04 +08:00
|
|
|
|
sched: fix copy_namespace() <-> sched_fork() dependency in do_fork
Sukadev Bhattiprolu reported a kernel crash with control groups.
There are couple of problems discovered by Suka's test:
- The test requires the cgroup filesystem to be mounted with
atleast the cpu and ns options (i.e both namespace and cpu
controllers are active in the same hierarchy).
# mkdir /dev/cpuctl
# mount -t cgroup -ocpu,ns none cpuctl
(or simply)
# mount -t cgroup none cpuctl -> Will activate all controllers
in same hierarchy.
- The test invokes clone() with CLONE_NEWNS set. This causes a a new child
to be created, also a new group (do_fork->copy_namespaces->ns_cgroup_clone->
cgroup_clone) and the child is attached to the new group (cgroup_clone->
attach_task->sched_move_task). At this point in time, the child's scheduler
related fields are uninitialized (including its on_rq field, which it has
inherited from parent). As a result sched_move_task thinks its on
runqueue, when it isn't.
As a solution to this problem, I moved sched_fork() call, which
initializes scheduler related fields on a new task, before
copy_namespaces(). I am not sure though whether moving up will
cause other side-effects. Do you see any issue?
- The second problem exposed by this test is that task_new_fair()
assumes that parent and child will be part of the same group (which
needn't be as this test shows). As a result, cfs_rq->curr can be NULL
for the child.
The solution is to test for curr pointer being NULL in
task_new_fair().
With the patch below, I could run ns_exec() fine w/o a crash.
Reported-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2007-11-10 05:39:39 +08:00
|
|
|
/* 'curr' will be NULL if the child belongs to a different group */
|
2007-10-15 23:00:14 +08:00
|
|
|
if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
|
sched: fix copy_namespace() <-> sched_fork() dependency in do_fork
Sukadev Bhattiprolu reported a kernel crash with control groups.
There are couple of problems discovered by Suka's test:
- The test requires the cgroup filesystem to be mounted with
atleast the cpu and ns options (i.e both namespace and cpu
controllers are active in the same hierarchy).
# mkdir /dev/cpuctl
# mount -t cgroup -ocpu,ns none cpuctl
(or simply)
# mount -t cgroup none cpuctl -> Will activate all controllers
in same hierarchy.
- The test invokes clone() with CLONE_NEWNS set. This causes a a new child
to be created, also a new group (do_fork->copy_namespaces->ns_cgroup_clone->
cgroup_clone) and the child is attached to the new group (cgroup_clone->
attach_task->sched_move_task). At this point in time, the child's scheduler
related fields are uninitialized (including its on_rq field, which it has
inherited from parent). As a result sched_move_task thinks its on
runqueue, when it isn't.
As a solution to this problem, I moved sched_fork() call, which
initializes scheduler related fields on a new task, before
copy_namespaces(). I am not sure though whether moving up will
cause other side-effects. Do you see any issue?
- The second problem exposed by this test is that task_new_fair()
assumes that parent and child will be part of the same group (which
needn't be as this test shows). As a result, cfs_rq->curr can be NULL
for the child.
The solution is to test for curr pointer being NULL in
task_new_fair().
With the patch below, I could run ns_exec() fine w/o a crash.
Reported-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2007-11-10 05:39:39 +08:00
|
|
|
curr && curr->vruntime < se->vruntime) {
|
2007-10-15 23:00:08 +08:00
|
|
|
/*
|
2007-10-15 23:00:08 +08:00
|
|
|
* Upon rescheduling, sched_class::put_prev_task() will place
|
|
|
|
* 'current' within the tree based on its new key value.
|
|
|
|
*/
|
2007-10-15 23:00:04 +08:00
|
|
|
swap(curr->vruntime, se->vruntime);
|
2008-08-28 17:12:49 +08:00
|
|
|
resched_task(rq->curr);
|
2007-10-15 23:00:04 +08:00
|
|
|
}
|
2007-07-10 00:51:58 +08:00
|
|
|
|
2007-10-17 22:55:11 +08:00
|
|
|
enqueue_task_fair(rq, p, 0);
|
2007-07-10 00:51:58 +08:00
|
|
|
}
|
|
|
|
|
2008-01-26 04:08:22 +08:00
|
|
|
/*
|
|
|
|
* 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
|
2008-09-21 05:38:02 +08:00
|
|
|
check_preempt_curr(rq, p, 0);
|
2008-01-26 04:08:22 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* 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
|
2008-09-21 05:38:02 +08:00
|
|
|
check_preempt_curr(rq, p, 0);
|
2008-01-26 04:08:22 +08:00
|
|
|
}
|
|
|
|
|
2007-10-15 23:00:08 +08:00
|
|
|
/* 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);
|
|
|
|
}
|
|
|
|
|
2008-03-01 04:21:01 +08:00
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
|
|
static void moved_group_fair(struct task_struct *p)
|
|
|
|
{
|
|
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(p);
|
|
|
|
|
|
|
|
update_curr(cfs_rq);
|
|
|
|
place_entity(cfs_rq, &p->se, 1);
|
|
|
|
}
|
|
|
|
#endif
|
|
|
|
|
2007-07-10 00:51:58 +08:00
|
|
|
/*
|
|
|
|
* All the scheduling class methods:
|
|
|
|
*/
|
2007-10-15 23:00:12 +08:00
|
|
|
static const struct sched_class fair_sched_class = {
|
|
|
|
.next = &idle_sched_class,
|
2007-07-10 00:51:58 +08:00
|
|
|
.enqueue_task = enqueue_task_fair,
|
|
|
|
.dequeue_task = dequeue_task_fair,
|
|
|
|
.yield_task = yield_task_fair,
|
|
|
|
|
2007-10-15 23:00:05 +08:00
|
|
|
.check_preempt_curr = check_preempt_wakeup,
|
2007-07-10 00:51:58 +08:00
|
|
|
|
|
|
|
.pick_next_task = pick_next_task_fair,
|
|
|
|
.put_prev_task = put_prev_task_fair,
|
|
|
|
|
2007-10-25 00:23:51 +08:00
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#ifdef CONFIG_SMP
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2008-10-22 15:25:26 +08:00
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.select_task_rq = select_task_rq_fair,
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2007-07-10 00:51:58 +08:00
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.load_balance = load_balance_fair,
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2007-10-25 00:23:51 +08:00
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.move_one_task = move_one_task_fair,
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2007-10-25 00:23:51 +08:00
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#endif
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2007-07-10 00:51:58 +08:00
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2007-10-15 23:00:08 +08:00
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.set_curr_task = set_curr_task_fair,
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2007-07-10 00:51:58 +08:00
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.task_tick = task_tick_fair,
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.task_new = task_new_fair,
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2008-01-26 04:08:22 +08:00
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.prio_changed = prio_changed_fair,
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.switched_to = switched_to_fair,
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2008-03-01 04:21:01 +08:00
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#ifdef CONFIG_FAIR_GROUP_SCHED
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.moved_group = moved_group_fair,
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#endif
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2007-07-10 00:51:58 +08:00
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};
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#ifdef CONFIG_SCHED_DEBUG
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2007-08-09 17:16:47 +08:00
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static void print_cfs_stats(struct seq_file *m, int cpu)
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2007-07-10 00:51:58 +08:00
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{
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struct cfs_rq *cfs_rq;
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2008-01-26 04:08:34 +08:00
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rcu_read_lock();
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2007-08-09 17:16:51 +08:00
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for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
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2007-08-09 17:16:47 +08:00
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print_cfs_rq(m, cpu, cfs_rq);
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2008-01-26 04:08:34 +08:00
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rcu_read_unlock();
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2007-07-10 00:51:58 +08:00
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}
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#endif
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