osfmk/kern/priority.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * @OSF_COPYRIGHT@
  24  */
  25 /*
  26  * Mach Operating System
  27  * Copyright (c) 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  Software.Distribution@CS.CMU.EDU
  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  */
  52 /*
  53  *      File:   clock_prim.c
  54  *      Author: Avadis Tevanian, Jr.
  55  *      Date:   1986
  56  *
  57  *      Clock primitives.
  58  */
  59
  60 #include <cpus.h>
  61
  62 #include <mach/boolean.h>
  63 #include <mach/kern_return.h>
  64 #include <mach/machine.h>
  65 #include <kern/host.h>
  66 #include <kern/mach_param.h>
  67 #include <kern/sched.h>
  68 #include <kern/spl.h>
  69 #include <kern/thread.h>
  70 #include <kern/processor.h>
  71 #include <machine/machparam.h>
  72 #include <kern/sf.h>
  73 #include <kern/mk_sp.h> /*** ??? fix so this can be removed ***/
  74 /*** ??? Should this file be MK SP-specific?  Or is it more general purpose? ***/
  75
  76
  77
  78 /*
  79  *      USAGE_THRESHOLD is the amount by which usage must change to
  80  *      cause a priority shift that moves a thread between run queues.
  81  */
  82
  83 #ifdef  PRI_SHIFT_2
  84 #if     PRI_SHIFT_2 > 0
  85 #define USAGE_THRESHOLD (((1 << PRI_SHIFT) + (1 << PRI_SHIFT_2)) << (2 + SCHED_SHIFT))
  86 #else   /* PRI_SHIFT_2 > 0 */
  87 #define USAGE_THRESHOLD (((1 << PRI_SHIFT) - (1 << -(PRI_SHIFT_2))) << (2 + SCHED_SHIFT))
  88 #endif  /* PRI_SHIFT_2 > 0 */
  89 #else   /* PRI_SHIFT_2 */
  90 #define USAGE_THRESHOLD (1 << (PRI_SHIFT + 2 + SCHED_SHIFT))
  91 #endif  /* PRI_SHIFT_2 */
  92
  93 /*
  94  *      thread_quantum_update:
  95  *
  96  *      Recalculate the quantum and priority for a thread.
  97  *      The number of ticks that has elapsed since we were last called
  98  *      is passed as "nticks."
  99  */
 100
 101 void
 102 thread_quantum_update(
 103         register int            mycpu,
 104         register thread_t       thread,
 105         int                                     nticks,
 106         int                                     state)
 107 {
 108         register int                            quantum;
 109         register processor_t            myprocessor;
 110         register processor_set_t        pset;
 111         spl_t                                           s;
 112
 113         myprocessor = cpu_to_processor(mycpu);
 114         pset = myprocessor->processor_set;
 115
 116         /*
 117          *      Account for thread's utilization of these ticks.
 118          *      This assumes that there is *always* a current thread.
 119          *      When the processor is idle, it should be the idle thread.
 120          */
 121
 122         /*
 123          *      Update set_quantum and calculate the current quantum.
 124          */
 125         pset->set_quantum = pset->machine_quantum[
 126                                                         (pset->runq.count > pset->processor_count) ?
 127                                                                   pset->processor_count : pset->runq.count];
 128
 129         if (myprocessor->runq.count != 0)
 130                 quantum = min_quantum;
 131         else
 132                 quantum = pset->set_quantum;
 133
 134         /*
 135          *      Now recompute the priority of the thread if appropriate.
 136          */
 137
 138         {
 139                 s = splsched();
 140                 thread_lock(thread);
 141
 142                 if (!(thread->policy & (POLICY_TIMESHARE|POLICY_RR|POLICY_FIFO))) {
 143                         thread_unlock(thread);
 144                         splx(s);
 145                         return;
 146                 }
 147
 148                 if (thread->state&TH_IDLE) {
 149                         /* Don't try to time-slice idle threads */
 150                         myprocessor->first_quantum = TRUE;
 151                         if (thread->sched_stamp != sched_tick)
 152                                 update_priority(thread);
 153                         thread_unlock(thread);
 154                         splx(s);
 155                         ast_check();
 156                         return;
 157                 }
 158
 159                 myprocessor->quantum -= nticks;
 160                 /*
 161                  *      Runtime quantum adjustment.  Use quantum_adj_index
 162                  *      to avoid synchronizing quantum expirations.
 163                  */
 164                 if (    quantum != myprocessor->last_quantum    &&
 165                                         pset->processor_count > 1                                       ) {
 166                         myprocessor->last_quantum = quantum;
 167                         simple_lock(&pset->quantum_adj_lock);
 168                         quantum = min_quantum + (pset->quantum_adj_index *
 169                                                                                         (quantum - min_quantum)) /
 170                                                                                                 (pset->processor_count - 1);
 171                         if (++(pset->quantum_adj_index) >= pset->processor_count)
 172                                 pset->quantum_adj_index = 0;
 173                         simple_unlock(&pset->quantum_adj_lock);
 174                 }
 175                 if (myprocessor->quantum <= 0) {
 176                         if (thread->sched_stamp != sched_tick)
 177                                 update_priority(thread);
 178                         else
 179                         if (    thread->policy == POLICY_TIMESHARE              &&
 180                                         thread->depress_priority < 0                            ) {
 181                                 thread_timer_delta(thread);
 182                                 thread->sched_usage += thread->sched_delta;
 183                                 thread->sched_delta = 0;
 184                                 compute_my_priority(thread);
 185                         }
 186
 187                         /*
 188                          *      This quantum is up, give this thread another.
 189                          */
 190                         myprocessor->first_quantum = FALSE;
 191                         if (thread->policy == POLICY_TIMESHARE)
 192                                 myprocessor->quantum += quantum;
 193                         else
 194                                 myprocessor->quantum += min_quantum;
 195                 }
 196                 /*
 197                  *      Recompute priority if appropriate.
 198                  */
 199                 else {
 200                     if (thread->sched_stamp != sched_tick)
 201                                 update_priority(thread);
 202                     else
 203                         if (    thread->policy == POLICY_TIMESHARE              &&
 204                                         thread->depress_priority < 0                            ) {
 205                                 thread_timer_delta(thread);
 206                                 if (thread->sched_delta >= USAGE_THRESHOLD) {
 207                                     thread->sched_usage +=      thread->sched_delta;
 208                                     thread->sched_delta = 0;
 209                                     compute_my_priority(thread);
 210                                 }
 211                         }
 212                 }
 213
 214                 thread_unlock(thread);
 215                 splx(s);
 216
 217                 /*
 218                  * Check for and schedule ast if needed.
 219                  */
 220                 ast_check();
 221         }
 222 }