The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/i386/timer.h

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    1 /* 
    2  * Mach Operating System
    3  * Copyright (c) 1993,1991 Carnegie Mellon University
    4  * All Rights Reserved.
    5  * 
    6  * Permission to use, copy, modify and distribute this software and its
    7  * documentation is hereby granted, provided that both the copyright
    8  * notice and this permission notice appear in all copies of the
    9  * software, derivative works or modified versions, and any portions
   10  * thereof, and that both notices appear in supporting documentation.
   11  * 
   12  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
   13  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
   14  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   15  * 
   16  * Carnegie Mellon requests users of this software to return to
   17  * 
   18  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   19  *  School of Computer Science
   20  *  Carnegie Mellon University
   21  *  Pittsburgh PA 15213-3890
   22  * 
   23  * any improvements or extensions that they make and grant Carnegie Mellon 
   24  * the rights to redistribute these changes.
   25  */
   26 
   27 /*
   28  * HISTORY
   29  * $Log:        timer.h,v $
   30  * Revision 2.3  93/11/17  16:40:16  dbg
   31  *      Added TIMER_TO_TIMESPEC.
   32  *      [93/04/15            dbg]
   33  * 
   34  *      Changed TIMER_RATE to USAGE_RATE.
   35  *      [93/02/23            dbg]
   36  * 
   37  * Revision 2.2  91/07/31  17:41:51  dbg
   38  *      Created.
   39  *      [91/07/30  16:58:38  dbg]
   40  * 
   41  */
   42 
   43 #ifndef _I386_TIMER_H_
   44 #define _I386_TIMER_H_
   45 
   46 /*
   47  *      Machine dependent timer definitions.
   48  */
   49 
   50 #include <platforms.h>
   51 
   52 #ifdef  SYMMETRY
   53 
   54 /*
   55  *      TIMER_MAX is not used on the Sequent because a 32-bit rollover
   56  *      timer does not need to be adjusted for maximum value.
   57  */
   58 
   59 /*
   60  *      USAGE_RATE is the rate of the timer in ticks per second.
   61  *      It is used to calculate percent cpu usage.
   62  */
   63 
   64 #define USAGE_RATE      1000000
   65 
   66 /*
   67  *      TIMER_HIGH_UNIT is the unit for high_bits in terms of low_bits.
   68  *      Setting it to USAGE_RATE makes the high unit seconds.
   69  */
   70 
   71 #define TIMER_HIGH_UNIT USAGE_RATE
   72 
   73 /*
   74  *      These routines convert the components of a timer
   75  *      to USAGE_RATE.
   76  *
   77  *      For the Sequent, since the low unit is microseconds,
   78  *      TIMER_LOW_TO_USAGE is the identity function.
   79  */
   80 #define TIMER_LOW_TO_USAGE(micros)      (micros)
   81 #define TIMER_HIGH_TO_USAGE(secs)       ((secs)*TIMER_HIGH_UNIT)
   82 
   83 /*
   84  *      TIMER_TO_TIMESPEC is used to adjust the value of a timer after
   85  *      it has been copied into a time_spec_t.
   86  *
   87  *      We convert the low word from microseconds to nanoseconds.
   88  *      The high word is already in seconds.
   89  *
   90  *      We normalize the result before conversion, since the
   91  *      multiplication may overflow 32 bits.
   92  */
   93 #define TIMER_TO_TIMESPEC(timer) \
   94         ((timer)->high += (timer)->low / TIMER_HIGH_UNIT, \
   95          (timer)->low = ((timer)->low % TIMER_HIGH_UNIT) * 1000)
   96         
   97 /*
   98  *      MACHINE_TIMER_ROUTINES should be defined if the timer routines are
   99  *      implemented in machine-dependent code (e.g. assembly language).
  100  */
  101 #define MACHINE_TIMER_ROUTINES
  102 
  103 #endif
  104 
  105 #endif  /* _I386_TIMER_H_ */

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