sched_dualq.c   [plain text]

/*
 * Copyright (c) 2013 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,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
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#include <mach/mach_types.h>
#include <mach/machine.h>

#include <machine/machine_routines.h>
#include <machine/sched_param.h>
#include <machine/machine_cpu.h>

#include <kern/kern_types.h>
#include <kern/debug.h>
#include <kern/machine.h>
#include <kern/misc_protos.h>
#include <kern/processor.h>
#include <kern/queue.h>
#include <kern/sched.h>
#include <kern/sched_prim.h>
#include <kern/task.h>
#include <kern/thread.h>

#include <sys/kdebug.h>

static void
sched_dualq_init(void);

static thread_t
sched_dualq_steal_thread(processor_set_t pset);

static void
sched_dualq_thread_update_scan(sched_update_scan_context_t scan_context);

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

static boolean_t
sched_dualq_processor_queue_remove(processor_t processor, thread_t thread);

static ast_t
sched_dualq_processor_csw_check(processor_t processor);

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

static int
sched_dualq_runq_count(processor_t processor);

static boolean_t
sched_dualq_processor_queue_empty(processor_t processor);

static uint64_t
sched_dualq_runq_stats_count_sum(processor_t processor);

static int
sched_dualq_processor_bound_count(processor_t processor);

static void
sched_dualq_pset_init(processor_set_t pset);

static void
sched_dualq_processor_init(processor_t processor);

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

static void
sched_dualq_processor_queue_shutdown(processor_t processor);

static sched_mode_t
sched_dualq_initial_thread_sched_mode(task_t parent_task);

const struct sched_dispatch_table sched_dualq_dispatch = {
	.sched_name                                     = "dualq",
	.init                                           = sched_dualq_init,
	.timebase_init                                  = sched_timeshare_timebase_init,
	.processor_init                                 = sched_dualq_processor_init,
	.pset_init                                      = sched_dualq_pset_init,
	.maintenance_continuation                       = sched_timeshare_maintenance_continue,
	.choose_thread                                  = sched_dualq_choose_thread,
	.steal_thread_enabled                           = TRUE,
	.steal_thread                                   = sched_dualq_steal_thread,
	.compute_timeshare_priority                     = sched_compute_timeshare_priority,
	.choose_processor                               = choose_processor,
	.processor_enqueue                              = sched_dualq_processor_enqueue,
	.processor_queue_shutdown                       = sched_dualq_processor_queue_shutdown,
	.processor_queue_remove                         = sched_dualq_processor_queue_remove,
	.processor_queue_empty                          = sched_dualq_processor_queue_empty,
	.priority_is_urgent                             = priority_is_urgent,
	.processor_csw_check                            = sched_dualq_processor_csw_check,
	.processor_queue_has_priority                   = sched_dualq_processor_queue_has_priority,
	.initial_quantum_size                           = sched_timeshare_initial_quantum_size,
	.initial_thread_sched_mode                      = sched_dualq_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_dualq_runq_count,
	.processor_runq_stats_count_sum                 = sched_dualq_runq_stats_count_sum,
	.processor_bound_count                          = sched_dualq_processor_bound_count,
	.thread_update_scan                             = sched_dualq_thread_update_scan,
	.direct_dispatch_to_idle_processors             = FALSE,
	.multiple_psets_enabled                         = TRUE,
	.sched_groups_enabled                           = FALSE,
};

__attribute__((always_inline))
static inline run_queue_t dualq_main_runq(processor_t processor)
{
	return &processor->processor_set->pset_runq;
}

__attribute__((always_inline))
static inline run_queue_t dualq_bound_runq(processor_t processor)
{
	return &processor->runq;
}

__attribute__((always_inline))
static inline run_queue_t dualq_runq_for_thread(processor_t processor, thread_t thread)
{
	if (thread->bound_processor == PROCESSOR_NULL) {
		return dualq_main_runq(processor);
	} else {
		assert(thread->bound_processor == processor);
		return dualq_bound_runq(processor);
	}
}

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

static void
sched_dualq_processor_init(processor_t processor)
{
	run_queue_init(&processor->runq);
}

static void
sched_dualq_pset_init(processor_set_t pset)
{
	run_queue_init(&pset->pset_runq);
}

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

static thread_t
sched_dualq_choose_thread(
                          processor_t      processor,
                          int              priority,
                 __unused ast_t            reason)
{
	run_queue_t main_runq  = dualq_main_runq(processor);
	run_queue_t bound_runq = dualq_bound_runq(processor);
	run_queue_t chosen_runq;

	if (bound_runq->highq < priority &&
	     main_runq->highq < priority)
		return THREAD_NULL;

	if (bound_runq->count && main_runq->count) {
		if (bound_runq->highq >= main_runq->highq) {
			chosen_runq = bound_runq;
		} else {
			chosen_runq = main_runq;
		}
	} else if (bound_runq->count) {
		chosen_runq = bound_runq;
	} else if (main_runq->count) {
		chosen_runq = main_runq;
	} else {
		return (THREAD_NULL);
	}

	return run_queue_dequeue(chosen_runq, SCHED_HEADQ);
}

static boolean_t
sched_dualq_processor_enqueue(
                              processor_t       processor,
                              thread_t          thread,
                              integer_t         options)
{
	run_queue_t     rq = dualq_runq_for_thread(processor, thread);
	boolean_t       result;

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

	return (result);
}

static boolean_t
sched_dualq_processor_queue_empty(processor_t processor)
{
	return dualq_main_runq(processor)->count  == 0 &&
	       dualq_bound_runq(processor)->count == 0;
}

static ast_t
sched_dualq_processor_csw_check(processor_t processor)
{
	boolean_t       has_higher;
	int             pri;

	run_queue_t main_runq  = dualq_main_runq(processor);
	run_queue_t bound_runq = dualq_bound_runq(processor);

	assert(processor->active_thread != NULL);

	pri = MAX(main_runq->highq, bound_runq->highq);

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

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

		if (bound_runq->urgency > 0)
			return (AST_PREEMPT | AST_URGENT);
		
		return AST_PREEMPT;
	}

	return AST_NONE;
}

static boolean_t
sched_dualq_processor_queue_has_priority(processor_t    processor,
                                         int            priority,
                                         boolean_t      gte)
{
	int qpri = MAX(dualq_main_runq(processor)->highq, dualq_bound_runq(processor)->highq);

	if (gte)
		return qpri >= priority;
	else
		return qpri > priority;
}

static int
sched_dualq_runq_count(processor_t processor)
{
	return dualq_main_runq(processor)->count + dualq_bound_runq(processor)->count;
}

static uint64_t
sched_dualq_runq_stats_count_sum(processor_t processor)
{
	uint64_t bound_sum = dualq_bound_runq(processor)->runq_stats.count_sum;

	if (processor->cpu_id == processor->processor_set->cpu_set_low)
		return bound_sum + dualq_main_runq(processor)->runq_stats.count_sum;
	else
		return bound_sum;
}
static int
sched_dualq_processor_bound_count(processor_t processor)
{
	return dualq_bound_runq(processor)->count;
}

static void
sched_dualq_processor_queue_shutdown(processor_t processor)
{
	processor_set_t pset = processor->processor_set;
	run_queue_t     rq   = dualq_main_runq(processor);
	thread_t        thread;
	queue_head_t    tqueue;

	/* We only need to migrate threads if this is the last active processor in the pset */
	if (pset->online_processor_count > 0) {
		pset_unlock(pset);
		return;
	}

	queue_init(&tqueue);

	while (rq->count > 0) {
		thread = run_queue_dequeue(rq, SCHED_HEADQ);
		enqueue_tail(&tqueue, (queue_entry_t)thread);
	}

	pset_unlock(pset);

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

		thread_setrun(thread, SCHED_TAILQ);

		thread_unlock(thread);
	}
}

static boolean_t
sched_dualq_processor_queue_remove(
                                   processor_t processor,
                                   thread_t    thread)
{
	run_queue_t             rq;
	processor_set_t         pset = processor->processor_set;

	pset_lock(pset);

	rq = dualq_runq_for_thread(processor, thread);

	if (processor == thread->runq) {
		/*
		 * Thread is on a run queue and we have a lock on
		 * that run queue.
		 */
		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);
}

static thread_t
sched_dualq_steal_thread(processor_set_t pset)
{
	processor_set_t nset, cset = pset;
	thread_t        thread;

	do {
		if (cset->pset_runq.count > 0) {
			thread = run_queue_dequeue(&cset->pset_runq, SCHED_HEADQ);
			pset_unlock(cset);
			return (thread);
		}

		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_dualq_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;

	/*
	 *  We update the threads associated with each processor (bound and idle threads)
	 *  and then update the threads in each pset runqueue.
	 */

	do {
		do {
			pset = processor->processor_set;

			s = splsched();
			pset_lock(pset);

			restart_needed = runq_scan(dualq_bound_runq(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);

	pset = &pset0;

	do {
		do {
			s = splsched();
			pset_lock(pset);

			restart_needed = runq_scan(&pset->pset_runq, scan_context);

			pset_unlock(pset);
			splx(s);

			if (restart_needed)
				break;
		} while ((pset = pset->pset_list) != NULL);

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

	} while (restart_needed);
}