xnu-3248.30.4.tar.gz

[apple/xnu.git] / osfmk / kern / sched_traditional.c

/*
 * Copyright (c) 2000-2015 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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/*
 * @OSF_FREE_COPYRIGHT@
 */
/*
 * Mach Operating System
 * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
 * All Rights Reserved.
 *
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 *
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * Carnegie Mellon requests users of this software to return to
 *
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 *
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */

#include <mach/mach_types.h>

#include <kern/sched.h>
#include <kern/sched_prim.h>

static boolean_t
sched_traditional_use_pset_runqueue = FALSE;

static void
sched_traditional_init(void);

static thread_t
sched_traditional_steal_thread(processor_set_t pset);

static thread_t
sched_traditional_steal_processor_thread(processor_t processor);

static void
sched_traditional_thread_update_scan(sched_update_scan_context_t scan_context);

static void
sched_traditional_processor_queue_shutdown(processor_t processor);

static boolean_t
sched_traditional_processor_enqueue(processor_t processor, thread_t thread, integer_t options);

static boolean_t
sched_traditional_processor_queue_remove(processor_t processor, thread_t thread);

static boolean_t
sched_traditional_processor_queue_empty(processor_t processor);

static ast_t
sched_traditional_processor_csw_check(processor_t processor);

static boolean_t
sched_traditional_processor_queue_has_priority(processor_t processor, int priority, boolean_t gte);

static int
sched_traditional_processor_runq_count(processor_t processor);

static boolean_t
sched_traditional_with_pset_runqueue_processor_queue_empty(processor_t processor);

static uint64_t
sched_traditional_processor_runq_stats_count_sum(processor_t processor);

static uint64_t
sched_traditional_with_pset_runqueue_processor_runq_stats_count_sum(processor_t processor);

static int
sched_traditional_processor_bound_count(processor_t processor);

extern void
sched_traditional_quantum_expire(thread_t thread);

static void
sched_traditional_processor_init(processor_t processor);

static void
sched_traditional_pset_init(processor_set_t pset);

static void
sched_traditional_with_pset_runqueue_init(void);

static sched_mode_t
sched_traditional_initial_thread_sched_mode(task_t parent_task);

static thread_t
sched_traditional_choose_thread(processor_t processor, int priority, ast_t reason);

/* Choose a thread from a processor's priority-based runq */
static thread_t sched_traditional_choose_thread_from_runq(processor_t processor, run_queue_t runq, int priority);

const struct sched_dispatch_table sched_traditional_dispatch = {
        .sched_name                                     = "traditional",
        .init                                           = sched_traditional_init,
        .timebase_init                                  = sched_timeshare_timebase_init,
        .processor_init                                 = sched_traditional_processor_init,
        .pset_init                                      = sched_traditional_pset_init,
        .maintenance_continuation                       = sched_timeshare_maintenance_continue,
        .choose_thread                                  = sched_traditional_choose_thread,
        .steal_thread_enabled                           = TRUE,
        .steal_thread                                   = sched_traditional_steal_thread,
        .compute_timeshare_priority                     = sched_compute_timeshare_priority,
        .choose_processor                               = choose_processor,
        .processor_enqueue                              = sched_traditional_processor_enqueue,
        .processor_queue_shutdown                       = sched_traditional_processor_queue_shutdown,
        .processor_queue_remove                         = sched_traditional_processor_queue_remove,
        .processor_queue_empty                          = sched_traditional_processor_queue_empty,
        .priority_is_urgent                             = priority_is_urgent,
        .processor_csw_check                            = sched_traditional_processor_csw_check,
        .processor_queue_has_priority                   = sched_traditional_processor_queue_has_priority,
        .initial_quantum_size                           = sched_timeshare_initial_quantum_size,
        .initial_thread_sched_mode                      = sched_traditional_initial_thread_sched_mode,
        .can_update_priority                            = can_update_priority,
        .update_priority                                = update_priority,
        .lightweight_update_priority                    = lightweight_update_priority,
        .quantum_expire                                 = sched_default_quantum_expire,
        .processor_runq_count                           = sched_traditional_processor_runq_count,
        .processor_runq_stats_count_sum                 = sched_traditional_processor_runq_stats_count_sum,
        .processor_bound_count                          = sched_traditional_processor_bound_count,
        .thread_update_scan                             = sched_traditional_thread_update_scan,
        .direct_dispatch_to_idle_processors             = TRUE,
        .multiple_psets_enabled                         = TRUE,
        .sched_groups_enabled                           = FALSE,
};

const struct sched_dispatch_table sched_traditional_with_pset_runqueue_dispatch = {
        .sched_name                                     = "traditional_with_pset_runqueue",
        .init                                           = sched_traditional_with_pset_runqueue_init,
        .timebase_init                                  = sched_timeshare_timebase_init,
        .processor_init                                 = sched_traditional_processor_init,
        .pset_init                                      = sched_traditional_pset_init,
        .maintenance_continuation                       = sched_timeshare_maintenance_continue,
        .choose_thread                                  = sched_traditional_choose_thread,
        .steal_thread_enabled                           = TRUE,
        .steal_thread                                   = sched_traditional_steal_thread,
        .compute_timeshare_priority                     = sched_compute_timeshare_priority,
        .choose_processor                               = choose_processor,
        .processor_enqueue                              = sched_traditional_processor_enqueue,
        .processor_queue_shutdown                       = sched_traditional_processor_queue_shutdown,
        .processor_queue_remove                         = sched_traditional_processor_queue_remove,
        .processor_queue_empty                          = sched_traditional_with_pset_runqueue_processor_queue_empty,
        .priority_is_urgent                             = priority_is_urgent,
        .processor_csw_check                            = sched_traditional_processor_csw_check,
        .processor_queue_has_priority                   = sched_traditional_processor_queue_has_priority,
        .initial_quantum_size                           = sched_timeshare_initial_quantum_size,
        .initial_thread_sched_mode                      = sched_traditional_initial_thread_sched_mode,
        .can_update_priority                            = can_update_priority,
        .update_priority                                = update_priority,
        .lightweight_update_priority                    = lightweight_update_priority,
        .quantum_expire                                 = sched_default_quantum_expire,
        .processor_runq_count                           = sched_traditional_processor_runq_count,
        .processor_runq_stats_count_sum                 = sched_traditional_with_pset_runqueue_processor_runq_stats_count_sum,
        .processor_bound_count                          = sched_traditional_processor_bound_count,
        .thread_update_scan                             = sched_traditional_thread_update_scan,
        .direct_dispatch_to_idle_processors             = FALSE,
        .multiple_psets_enabled                         = TRUE,
        .sched_groups_enabled                           = FALSE,
};

static void
sched_traditional_init(void)
{
        sched_timeshare_init();
}

static void
sched_traditional_with_pset_runqueue_init(void)
{
        sched_timeshare_init();
        sched_traditional_use_pset_runqueue = TRUE;
}

static void
sched_traditional_processor_init(processor_t processor)
{
        if (!sched_traditional_use_pset_runqueue) {
                run_queue_init(&processor->runq);
        }
        processor->runq_bound_count = 0;
}

static void
sched_traditional_pset_init(processor_set_t pset)
{
        if (sched_traditional_use_pset_runqueue) {
                run_queue_init(&pset->pset_runq);
        }
        pset->pset_runq_bound_count = 0;
}

__attribute__((always_inline))
static inline run_queue_t runq_for_processor(processor_t processor)
{
        if (sched_traditional_use_pset_runqueue)
                return &processor->processor_set->pset_runq;
        else
                return &processor->runq;
}

__attribute__((always_inline))
static inline void runq_consider_incr_bound_count(processor_t processor,
                                                  thread_t thread)
{
        if (thread->bound_processor == PROCESSOR_NULL)
                return;

        assert(thread->bound_processor == processor);

        if (sched_traditional_use_pset_runqueue)
                processor->processor_set->pset_runq_bound_count++;

        processor->runq_bound_count++;
}

__attribute__((always_inline))
static inline void runq_consider_decr_bound_count(processor_t processor,
                                                  thread_t thread)
{
        if (thread->bound_processor == PROCESSOR_NULL)
                return;

        assert(thread->bound_processor == processor);

        if (sched_traditional_use_pset_runqueue)
                processor->processor_set->pset_runq_bound_count--;

        processor->runq_bound_count--;
}

static thread_t
sched_traditional_choose_thread(
                                processor_t     processor,
                                int             priority,
                       __unused ast_t           reason)
{
        thread_t thread;

        thread = sched_traditional_choose_thread_from_runq(processor, runq_for_processor(processor), priority);
        if (thread != THREAD_NULL) {
                runq_consider_decr_bound_count(processor, thread);
        }

        return thread;
}

/*
 *      sched_traditional_choose_thread_from_runq:
 *
 *      Locate a thread to execute from the processor run queue
 *      and return it.  Only choose a thread with greater or equal
 *      priority.
 *
 *      Associated pset must be locked.  Returns THREAD_NULL
 *      on failure.
 */
static thread_t
sched_traditional_choose_thread_from_runq(
                                          processor_t     processor,
                                          run_queue_t     rq,
                                          int             priority)
{
        queue_t         queue   = rq->queues + rq->highq;
        int             pri     = rq->highq;
        int             count   = rq->count;
        thread_t        thread;

        while (count > 0 && pri >= priority) {
                thread = (thread_t)(uintptr_t)queue_first(queue);
                while (!queue_end(queue, (queue_entry_t)thread)) {
                        if (thread->bound_processor == PROCESSOR_NULL ||
                            thread->bound_processor == processor) {
                                remqueue((queue_entry_t)thread);

                                thread->runq = PROCESSOR_NULL;
                                SCHED_STATS_RUNQ_CHANGE(&rq->runq_stats, rq->count);
                                rq->count--;
                                if (SCHED(priority_is_urgent)(pri)) {
                                        rq->urgency--; assert(rq->urgency >= 0);
                                }
                                if (queue_empty(queue)) {
                                        if (pri != IDLEPRI)
                                                clrbit(MAXPRI - pri, rq->bitmap);
                                        rq->highq = MAXPRI - ffsbit(rq->bitmap);
                                }

                                return (thread);
                        }
                        count--;

                        thread = (thread_t)(uintptr_t)queue_next((queue_entry_t)thread);
                }

                queue--; pri--;
        }

        return (THREAD_NULL);
}

static sched_mode_t
sched_traditional_initial_thread_sched_mode(task_t parent_task)
{
        if (parent_task == kernel_task)
                return TH_MODE_FIXED;
        else
                return TH_MODE_TIMESHARE;
}

/*
 *      sched_traditional_processor_enqueue:
 *
 *      Enqueue thread on a processor run queue.  Thread must be locked,
 *      and not already be on a run queue.
 *
 *      Returns TRUE if a preemption is indicated based on the state
 *      of the run queue.
 *
 *      The run queue must be locked (see thread_run_queue_remove()
 *      for more info).
 */
static boolean_t
sched_traditional_processor_enqueue(processor_t   processor,
                                    thread_t      thread,
                                    integer_t     options)
{
        run_queue_t     rq = runq_for_processor(processor);
        boolean_t       result;

        result = run_queue_enqueue(rq, thread, options);
        thread->runq = processor;
        runq_consider_incr_bound_count(processor, thread);

        return (result);
}

static boolean_t
sched_traditional_processor_queue_empty(processor_t processor)
{
        return runq_for_processor(processor)->count == 0;
}

static boolean_t
sched_traditional_with_pset_runqueue_processor_queue_empty(processor_t processor)
{
        processor_set_t pset = processor->processor_set;
        int count = runq_for_processor(processor)->count;

        /*
         * The pset runq contains the count of all runnable threads
         * for all processors in the pset. However, for threads that
         * are bound to another processor, the current "processor"
         * is not eligible to execute the thread. So we only
         * include bound threads that our bound to the current
         * "processor". This allows the processor to idle when the
         * count of eligible threads drops to 0, even if there's
         * a runnable thread bound to a different processor in the
         * shared runq.
         */

        count -= pset->pset_runq_bound_count;
        count += processor->runq_bound_count;

        return count == 0;
}

static ast_t
sched_traditional_processor_csw_check(processor_t processor)
{
        run_queue_t     runq;
        boolean_t       has_higher;

        assert(processor->active_thread != NULL);

        runq = runq_for_processor(processor);

        if (processor->first_timeslice) {
                has_higher = (runq->highq > processor->current_pri);
        } else {
                has_higher = (runq->highq >= processor->current_pri);
        }

        if (has_higher) {
                if (runq->urgency > 0)
                        return (AST_PREEMPT | AST_URGENT);

                return AST_PREEMPT;
        }

        return AST_NONE;
}

static boolean_t
sched_traditional_processor_queue_has_priority(processor_t      processor,
                                               int              priority,
                                               boolean_t        gte)
{
        if (gte)
                return runq_for_processor(processor)->highq >= priority;
        else
                return runq_for_processor(processor)->highq > priority;
}

static int
sched_traditional_processor_runq_count(processor_t processor)
{
        return runq_for_processor(processor)->count;
}

static uint64_t
sched_traditional_processor_runq_stats_count_sum(processor_t processor)
{
        return runq_for_processor(processor)->runq_stats.count_sum;
}

static uint64_t
sched_traditional_with_pset_runqueue_processor_runq_stats_count_sum(processor_t processor)
{
        if (processor->cpu_id == processor->processor_set->cpu_set_low)
                return runq_for_processor(processor)->runq_stats.count_sum;
        else
                return 0ULL;
}

static int
sched_traditional_processor_bound_count(processor_t processor)
{
        return processor->runq_bound_count;
}

/*
 *      sched_traditional_processor_queue_shutdown:
 *
 *      Shutdown a processor run queue by
 *      re-dispatching non-bound threads.
 *
 *      Associated pset must be locked, and is
 *      returned unlocked.
 */
static void
sched_traditional_processor_queue_shutdown(processor_t processor)
{
        processor_set_t         pset    = processor->processor_set;
        run_queue_t             rq      = runq_for_processor(processor);
        queue_t                 queue   = rq->queues + rq->highq;
        int                     pri     = rq->highq;
        int                     count   = rq->count;
        thread_t                next, thread;
        queue_head_t            tqueue;

        queue_init(&tqueue);

        while (count > 0) {
                thread = (thread_t)(uintptr_t)queue_first(queue);
                while (!queue_end(queue, (queue_entry_t)thread)) {
                        next = (thread_t)(uintptr_t)queue_next((queue_entry_t)thread);

                        if (thread->bound_processor == PROCESSOR_NULL) {
                                remqueue((queue_entry_t)thread);

                                thread->runq = PROCESSOR_NULL;
                                SCHED_STATS_RUNQ_CHANGE(&rq->runq_stats, rq->count);
                                runq_consider_decr_bound_count(processor, thread);
                                rq->count--;
                                if (SCHED(priority_is_urgent)(pri)) {
                                        rq->urgency--; assert(rq->urgency >= 0);
                                }
                                if (queue_empty(queue)) {
                                        if (pri != IDLEPRI)
                                                clrbit(MAXPRI - pri, rq->bitmap);
                                        rq->highq = MAXPRI - ffsbit(rq->bitmap);
                                }

                                enqueue_tail(&tqueue, (queue_entry_t)thread);
                        }
                        count--;

                        thread = next;
                }

                queue--; pri--;
        }

        pset_unlock(pset);

        while ((thread = (thread_t)(uintptr_t)dequeue_head(&tqueue)) != THREAD_NULL) {
                thread_lock(thread);

                thread_setrun(thread, SCHED_TAILQ);

                thread_unlock(thread);
        }
}

#if 0
static void
run_queue_check(
                run_queue_t     rq,
                thread_t        thread)
{
        queue_t         q;
        queue_entry_t   qe;

        if (rq != thread->runq)
                panic("run_queue_check: thread runq");

        if (thread->sched_pri > MAXPRI || thread->sched_pri < MINPRI)
                panic("run_queue_check: thread sched_pri");

        q = &rq->queues[thread->sched_pri];
        qe = queue_first(q);
        while (!queue_end(q, qe)) {
                if (qe == (queue_entry_t)thread)
                        return;

                qe = queue_next(qe);
        }

        panic("run_queue_check: end");
}
#endif /* 0 */

/*
 * Locks the runqueue itself.
 *
 * Thread must be locked.
 */
static boolean_t
sched_traditional_processor_queue_remove(processor_t processor,
                                         thread_t thread)
{
        processor_set_t pset;
        run_queue_t     rq;

        pset = processor->processor_set;
        pset_lock(pset);

        rq = runq_for_processor(processor);

        if (processor == thread->runq) {
                /*
                 * Thread is on a run queue and we have a lock on
                 * that run queue.
                 */
                runq_consider_decr_bound_count(processor, thread);
                run_queue_remove(rq, thread);
        }
        else {
                /*
                 * The thread left the run queue before we could
                 * lock the run queue.
                 */
                assert(thread->runq == PROCESSOR_NULL);
                processor = PROCESSOR_NULL;
        }

        pset_unlock(pset);

        return (processor != PROCESSOR_NULL);
}

/*
 *      sched_traditional_steal_processor_thread:
 *
 *      Locate a thread to steal from the processor and
 *      return it.
 *
 *      Associated pset must be locked.  Returns THREAD_NULL
 *      on failure.
 */
static thread_t
sched_traditional_steal_processor_thread(processor_t processor)
{
        run_queue_t     rq      = runq_for_processor(processor);
        queue_t         queue   = rq->queues + rq->highq;
        int             pri     = rq->highq;
        int             count   = rq->count;
        thread_t        thread;

        while (count > 0) {
                thread = (thread_t)(uintptr_t)queue_first(queue);
                while (!queue_end(queue, (queue_entry_t)thread)) {
                        if (thread->bound_processor == PROCESSOR_NULL) {
                                remqueue((queue_entry_t)thread);

                                thread->runq = PROCESSOR_NULL;
                                SCHED_STATS_RUNQ_CHANGE(&rq->runq_stats, rq->count);
                                runq_consider_decr_bound_count(processor, thread);
                                rq->count--;
                                if (SCHED(priority_is_urgent)(pri)) {
                                        rq->urgency--; assert(rq->urgency >= 0);
                                }
                                if (queue_empty(queue)) {
                                        if (pri != IDLEPRI)
                                                clrbit(MAXPRI - pri, rq->bitmap);
                                        rq->highq = MAXPRI - ffsbit(rq->bitmap);
                                }

                                return (thread);
                        }
                        count--;

                        thread = (thread_t)(uintptr_t)queue_next((queue_entry_t)thread);
                }

                queue--; pri--;
        }

        return (THREAD_NULL);
}

/*
 *      Locate and steal a thread, beginning
 *      at the pset.
 *
 *      The pset must be locked, and is returned
 *      unlocked.
 *
 *      Returns the stolen thread, or THREAD_NULL on
 *      failure.
 */
static thread_t
sched_traditional_steal_thread(processor_set_t pset)
{
        processor_set_t nset, cset = pset;
        processor_t     processor;
        thread_t        thread;

        do {
                processor = (processor_t)(uintptr_t)queue_first(&cset->active_queue);
                while (!queue_end(&cset->active_queue, (queue_entry_t)processor)) {
                        if (runq_for_processor(processor)->count > 0) {
                                thread = sched_traditional_steal_processor_thread(processor);
                                if (thread != THREAD_NULL) {
                                        remqueue((queue_entry_t)processor);
                                        enqueue_tail(&cset->active_queue, (queue_entry_t)processor);

                                        pset_unlock(cset);

                                        return (thread);
                                }
                        }

                        processor = (processor_t)(uintptr_t)queue_next((queue_entry_t)processor);
                }

                nset = next_pset(cset);

                if (nset != pset) {
                        pset_unlock(cset);

                        cset = nset;
                        pset_lock(cset);
                }
        } while (nset != pset);

        pset_unlock(cset);

        return (THREAD_NULL);
}

static void
sched_traditional_thread_update_scan(sched_update_scan_context_t scan_context)
{
        boolean_t       restart_needed = FALSE;
        processor_t     processor = processor_list;
        processor_set_t pset;
        thread_t        thread;
        spl_t           s;

        do {
                do {
                        /*
                         * TODO: in sched_traditional_use_pset_runqueue case,
                         *  avoid scanning the same runq multiple times
                         */
                        pset = processor->processor_set;

                        s = splsched();
                        pset_lock(pset);

                        restart_needed = runq_scan(runq_for_processor(processor), scan_context);

                        pset_unlock(pset);
                        splx(s);

                        if (restart_needed)
                                break;

                        thread = processor->idle_thread;
                        if (thread != THREAD_NULL && thread->sched_stamp != sched_tick) {
                                if (thread_update_add_thread(thread) == FALSE) {
                                        restart_needed = TRUE;
                                        break;
                                }
                        }
                } while ((processor = processor->processor_list) != NULL);

                /* Ok, we now have a collection of candidates -- fix them. */
                thread_update_process_threads();
        } while (restart_needed);
}