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Annotation of kernel/kern/priority.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
        !             7:  * Reserved.  This file contains Original Code and/or Modifications of
        !             8:  * Original Code as defined in and that are subject to the Apple Public
        !             9:  * Source License Version 1.1 (the "License").  You may not use this file
        !            10:  * except in compliance with the License.  Please obtain a copy of the
        !            11:  * License at http://www.apple.com/publicsource and read it before using
        !            12:  * this file.
        !            13:  * 
        !            14:  * The Original Code and all software distributed under the License are
        !            15:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            16:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            17:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            19:  * License for the specific language governing rights and limitations
        !            20:  * under the License.
        !            21:  * 
        !            22:  * @APPLE_LICENSE_HEADER_END@
        !            23:  */
        !            24: 
        !            25: /* 
        !            26:  * Mach Operating System
        !            27:  * Copyright (c) 1993,1991,1990,1989,1988,1987 Carnegie Mellon University
        !            28:  * All Rights Reserved.
        !            29:  * 
        !            30:  * Permission to use, copy, modify and distribute this software and its
        !            31:  * documentation is hereby granted, provided that both the copyright
        !            32:  * notice and this permission notice appear in all copies of the
        !            33:  * software, derivative works or modified versions, and any portions
        !            34:  * thereof, and that both notices appear in supporting documentation.
        !            35:  * 
        !            36:  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
        !            37:  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
        !            38:  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
        !            39:  * 
        !            40:  * Carnegie Mellon requests users of this software to return to
        !            41:  * 
        !            42:  *  Software Distribution Coordinator  or  [email protected]
        !            43:  *  School of Computer Science
        !            44:  *  Carnegie Mellon University
        !            45:  *  Pittsburgh PA 15213-3890
        !            46:  * 
        !            47:  * any improvements or extensions that they make and grant Carnegie Mellon
        !            48:  * the rights to redistribute these changes.
        !            49:  */
        !            50: /*
        !            51:  *     File:   clock_prim.c
        !            52:  *     Author: Avadis Tevanian, Jr.
        !            53:  *     Date:   1986
        !            54:  *
        !            55:  *     Clock primitives.
        !            56:  */
        !            57: 
        !            58: #include <cpus.h>
        !            59: 
        !            60: #include <mach/boolean.h>
        !            61: #include <mach/kern_return.h>
        !            62: #include <mach/machine.h>
        !            63: #include <kern/host.h>
        !            64: #include <kern/mach_param.h>
        !            65: #include <kern/sched.h>
        !            66: #include <kern/thread.h>
        !            67: #include <kern/time_out.h>
        !            68: #include <kern/time_stamp.h>
        !            69: #include <machine/machspl.h>
        !            70: 
        !            71: 
        !            72: 
        !            73: /*
        !            74:  *     USAGE_THRESHOLD is the amount by which usage must change to
        !            75:  *     cause a priority shift that moves a thread between run queues.
        !            76:  */
        !            77: 
        !            78: #ifdef PRI_SHIFT_2
        !            79: #if    PRI_SHIFT_2 > 0
        !            80: #define        USAGE_THRESHOLD (((1 << PRI_SHIFT) + (1 << PRI_SHIFT_2)) << (2 + SCHED_SHIFT))
        !            81: #else  /* PRI_SHIFT_2 > 0 */
        !            82: #define        USAGE_THRESHOLD (((1 << PRI_SHIFT) - (1 << -(PRI_SHIFT_2))) << (2 + SCHED_SHIFT))
        !            83: #endif /* PRI_SHIFT_2 > 0 */
        !            84: #else  /* PRI_SHIFT_2 */
        !            85: #define USAGE_THRESHOLD        (1 << (PRI_SHIFT + 2 + SCHED_SHIFT))
        !            86: #endif /* PRI_SHIFT_2 */
        !            87: 
        !            88: /*
        !            89:  *     thread_quantum_update:
        !            90:  *
        !            91:  *     Recalculate the quantum and priority for a thread.
        !            92:  *     The number of ticks that has elapsed since we were last called
        !            93:  *     is passed as "nticks."
        !            94:  */
        !            95: 
        !            96: void thread_quantum_update(mycpu, thread, nticks, state)
        !            97:        register int            mycpu;
        !            98:        register thread_t       thread;
        !            99:        int                     nticks;
        !           100:        int                     state;
        !           101: {
        !           102:        register int                    quantum;
        !           103:        register processor_t            myprocessor;
        !           104: #if    NCPUS > 1
        !           105:        register processor_set_t        pset;
        !           106: #endif
        !           107:        spl_t                           s;
        !           108: 
        !           109:        myprocessor = cpu_to_processor(mycpu);
        !           110: #if    NCPUS > 1
        !           111:        pset = myprocessor->processor_set;
        !           112:        if (pset == 0) {
        !           113:            /*
        !           114:             * Processor is being reassigned.
        !           115:             * Should rewrite processor assignment code to
        !           116:             * block clock interrupts.
        !           117:             */
        !           118:            return;
        !           119:        }
        !           120: #endif /* NCPUS > 1 */
        !           121: 
        !           122:        /*
        !           123:         *      Account for thread's utilization of these ticks.
        !           124:         *      This assumes that there is *always* a current thread.
        !           125:         *      When the processor is idle, it should be the idle thread.
        !           126:         */
        !           127: 
        !           128:        /*
        !           129:         *      Update set_quantum and calculate the current quantum.
        !           130:         */
        !           131: #if    NCPUS > 1
        !           132:        pset->set_quantum = pset->machine_quantum[
        !           133:                ((pset->runq.count > pset->processor_count) ?
        !           134:                  pset->processor_count : pset->runq.count)];
        !           135: 
        !           136:        if (myprocessor->runq.count != 0)
        !           137:                quantum = min_quantum;
        !           138:        else
        !           139:                quantum = pset->set_quantum;
        !           140: #else  /* NCPUS > 1 */
        !           141:        quantum = min_quantum;
        !           142:        default_pset.set_quantum = quantum;
        !           143: #endif /* NCPUS > 1 */
        !           144:                
        !           145:        /*
        !           146:         *      Now recompute the priority of the thread if appropriate.
        !           147:         */
        !           148: 
        !           149:        if (state != CPU_STATE_IDLE) {
        !           150:                myprocessor->quantum -= nticks;
        !           151: #if    NCPUS > 1
        !           152:                /*
        !           153:                 *      Runtime quantum adjustment.  Use quantum_adj_index
        !           154:                 *      to avoid synchronizing quantum expirations.
        !           155:                 */
        !           156:                if ((quantum != myprocessor->last_quantum) &&
        !           157:                    (pset->processor_count > 1)) {
        !           158:                        myprocessor->last_quantum = quantum;
        !           159:                        simple_lock(&pset->quantum_adj_lock);
        !           160:                        quantum = min_quantum + (pset->quantum_adj_index *
        !           161:                                (quantum - min_quantum)) / 
        !           162:                                        (pset->processor_count - 1);
        !           163:                        if (++(pset->quantum_adj_index) >=
        !           164:                            pset->processor_count)
        !           165:                                pset->quantum_adj_index = 0;
        !           166:                        simple_unlock(&pset->quantum_adj_lock);
        !           167:                }
        !           168: #endif /* NCPUS > 1 */
        !           169:                if (myprocessor->quantum <= 0) {
        !           170:                        s = splsched();
        !           171:                        thread_lock(thread);
        !           172:                        if (thread->sched_stamp != sched_tick) {
        !           173: #if    NCPUS > 1
        !           174:                                update_priority(thread);
        !           175: #endif /* NCPUS > 1 */
        !           176:                        }
        !           177:                        else {
        !           178:                            if (
        !           179: #if    MACH_FIXPRI
        !           180:                                (thread->policy != POLICY_FIXEDPRI) &&
        !           181: #endif /* MACH_FIXPRI */
        !           182:                                (thread->depress_priority < 0)) {
        !           183:                                    thread_timer_delta(thread);
        !           184:                                    thread->sched_usage +=
        !           185:                                        thread->sched_delta;
        !           186:                                    thread->sched_delta = 0;
        !           187:                                    compute_my_priority(thread);
        !           188:                            }
        !           189:                        }
        !           190:                        thread_unlock(thread);
        !           191:                        (void) splx(s);
        !           192:                        /*
        !           193:                         *      This quantum is up, give this thread another.
        !           194:                         */
        !           195:                        myprocessor->first_quantum = FALSE;
        !           196: #if    MACH_FIXPRI
        !           197:                        if (thread->policy != POLICY_FIXEDPRI) {
        !           198: #endif /* MACH_FIXPRI */
        !           199:                                myprocessor->quantum += quantum;
        !           200: #if    MACH_FIXPRI
        !           201:                        }
        !           202:                        else {
        !           203:                                /*
        !           204:                                 *    Fixed priority has per-thread quantum.
        !           205:                                 *    
        !           206:                                 */
        !           207:                                myprocessor->quantum += thread->sched_data;
        !           208:                        }
        !           209: #endif /* MACH_FIXPRI */
        !           210:                }
        !           211:                /*
        !           212:                 *      Recompute priority if appropriate.
        !           213:                 */
        !           214:                else {
        !           215:                    s = splsched();
        !           216:                    thread_lock(thread);
        !           217:                    if (thread->sched_stamp != sched_tick) {
        !           218: #if    NCPUS > 1
        !           219:                        update_priority(thread);
        !           220: #endif /* NCPUS > 1 */
        !           221:                    }
        !           222:                    else {
        !           223:                        if (
        !           224: #if    MACH_FIXPRI
        !           225:                            (thread->policy != POLICY_FIXEDPRI) &&
        !           226: #endif /* MACH_FIXPRI */
        !           227:                            (thread->depress_priority < 0)) {
        !           228:                                thread_timer_delta(thread);
        !           229:                                if (thread->sched_delta >= USAGE_THRESHOLD) {
        !           230:                                    thread->sched_usage +=
        !           231:                                        thread->sched_delta;
        !           232:                                    thread->sched_delta = 0;
        !           233:                                    compute_my_priority(thread);
        !           234:                                }
        !           235:                        }
        !           236:                    }
        !           237:                    thread_unlock(thread);
        !           238:                    (void) splx(s);
        !           239:                }
        !           240:                /*
        !           241:                 * Check for and schedule ast if needed.
        !           242:                 */
        !           243:                ast_check();
        !           244:        }
        !           245: }
        !           246: 

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