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/*
* Mach Operating System
* Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University.
* Copyright (c) 1993,1994 The University of Utah and
* the Computer Systems Laboratory (CSL).
* 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, THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF
* THIS SOFTWARE IN ITS "AS IS" CONDITION, AND DISCLAIM 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.
*/
/*
* File: priority.c
* Author: Avadis Tevanian, Jr.
* Date: 1986
*
* Clock primitives.
*/
#include <mach/boolean.h>
#include <mach/kern_return.h>
#include <mach/machine.h>
#include <kern/host.h>
#include <kern/mach_clock.h>
#include <kern/sched.h>
#include <kern/sched_prim.h>
#include <kern/thread.h>
#include <kern/processor.h>
#include <kern/timer.h>
#include <kern/time_stamp.h>
#include <machine/machspl.h>
/*
* USAGE_THRESHOLD is the amount by which usage must change to
* cause a priority shift that moves a thread between run queues.
*/
#ifdef PRI_SHIFT_2
#if PRI_SHIFT_2 > 0
#define USAGE_THRESHOLD (((1 << PRI_SHIFT) + (1 << PRI_SHIFT_2)) << (2 + SCHED_SHIFT))
#else /* PRI_SHIFT_2 > 0 */
#define USAGE_THRESHOLD (((1 << PRI_SHIFT) - (1 << -(PRI_SHIFT_2))) << (2 + SCHED_SHIFT))
#endif /* PRI_SHIFT_2 > 0 */
#else /* PRI_SHIFT_2 */
#define USAGE_THRESHOLD (1 << (PRI_SHIFT + 2 + SCHED_SHIFT))
#endif /* PRI_SHIFT_2 */
/*
* thread_quantum_update:
*
* Recalculate the quantum and priority for a thread.
* The number of ticks that has elapsed since we were last called
* is passed as "nticks."
*
* Called only from clock_interrupt().
*/
void thread_quantum_update(
int mycpu,
thread_t thread,
int nticks,
int state)
{
int quantum;
processor_t myprocessor;
#if NCPUS > 1
processor_set_t pset;
#endif
spl_t s;
myprocessor = cpu_to_processor(mycpu);
#if NCPUS > 1
pset = myprocessor->processor_set;
if (pset == 0) {
/*
* Processor is being reassigned.
* Should rewrite processor assignment code to
* block clock interrupts.
*/
return;
}
#endif /* NCPUS > 1 */
/*
* Account for thread's utilization of these ticks.
* This assumes that there is *always* a current thread.
* When the processor is idle, it should be the idle thread.
*/
/*
* Update set_quantum and calculate the current quantum.
*/
#if NCPUS > 1
pset->set_quantum = pset->machine_quantum[
((pset->runq.count > pset->processor_count) ?
pset->processor_count : pset->runq.count)];
if (myprocessor->runq.count != 0)
quantum = min_quantum;
else
quantum = pset->set_quantum;
#else /* NCPUS > 1 */
quantum = min_quantum;
default_pset.set_quantum = quantum;
#endif /* NCPUS > 1 */
/*
* Now recompute the priority of the thread if appropriate.
*/
if (state != CPU_STATE_IDLE) {
myprocessor->quantum -= nticks;
#if NCPUS > 1
/*
* Runtime quantum adjustment. Use quantum_adj_index
* to avoid synchronizing quantum expirations.
*/
if ((quantum != myprocessor->last_quantum) &&
(pset->processor_count > 1)) {
myprocessor->last_quantum = quantum;
simple_lock(&pset->quantum_adj_lock);
quantum = min_quantum + (pset->quantum_adj_index *
(quantum - min_quantum)) /
(pset->processor_count - 1);
if (++(pset->quantum_adj_index) >=
pset->processor_count)
pset->quantum_adj_index = 0;
simple_unlock(&pset->quantum_adj_lock);
}
#endif /* NCPUS > 1 */
if (myprocessor->quantum <= 0) {
s = splsched();
thread_lock(thread);
if (thread->sched_stamp != sched_tick) {
update_priority(thread);
}
else {
if (
#if MACH_FIXPRI
(thread->policy == POLICY_TIMESHARE) &&
#endif /* MACH_FIXPRI */
(thread->depress_priority < 0)) {
thread_timer_delta(thread);
thread->sched_usage +=
thread->sched_delta;
thread->sched_delta = 0;
compute_my_priority(thread);
}
}
thread_unlock(thread);
(void) splx(s);
/*
* This quantum is up, give this thread another.
*/
myprocessor->first_quantum = FALSE;
#if MACH_FIXPRI
if (thread->policy == POLICY_TIMESHARE) {
#endif /* MACH_FIXPRI */
myprocessor->quantum += quantum;
#if MACH_FIXPRI
}
else {
/*
* Fixed priority has per-thread quantum.
*
*/
myprocessor->quantum += thread->sched_data;
}
#endif /* MACH_FIXPRI */
}
/*
* Recompute priority if appropriate.
*/
else {
s = splsched();
thread_lock(thread);
if (thread->sched_stamp != sched_tick) {
update_priority(thread);
}
else {
if (
#if MACH_FIXPRI
(thread->policy == POLICY_TIMESHARE) &&
#endif /* MACH_FIXPRI */
(thread->depress_priority < 0)) {
thread_timer_delta(thread);
if (thread->sched_delta >= USAGE_THRESHOLD) {
thread->sched_usage +=
thread->sched_delta;
thread->sched_delta = 0;
compute_my_priority(thread);
}
}
}
thread_unlock(thread);
(void) splx(s);
}
/*
* Check for and schedule ast if needed.
*/
ast_check();
}
}
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