79b2073eea
The way time is apportioned to interrupt/system/user makes it impossible to guarantee monotonicity except by saving the previous value!
69 lines
2.7 KiB
C
69 lines
2.7 KiB
C
/* $NetBSD: clock.c,v 1.9 2003/08/19 08:31:18 dsl Exp $ */
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/*
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* Copyright (c) 1989, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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#if defined(LIBC_SCCS) && !defined(lint)
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#if 0
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static char sccsid[] = "@(#)clock.c 8.1 (Berkeley) 6/4/93";
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#else
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__RCSID("$NetBSD: clock.c,v 1.9 2003/08/19 08:31:18 dsl Exp $");
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#endif
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#endif /* LIBC_SCCS and not lint */
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#include <sys/param.h>
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#include <sys/time.h>
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#include <sys/resource.h>
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#include <time.h>
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/*
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* This code is all rather silly because the kernel counts actual
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* execution time (to usec accuracy) then splits it into user, system and
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* interrupt based on when clock ticks happen. getrusage apportions the
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* time based on the number of ticks, and here we are trying to generate
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* a number which was, traditionally, the number of ticks!
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*
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* Due to the way the time is apportioned, this code (and indeed getrusage
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* itself) are not guaranteed monotonic.
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*/
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clock_t
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clock()
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{
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struct rusage ru;
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clock_t hz = CLOCKS_PER_SEC;
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if (getrusage(RUSAGE_SELF, &ru))
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return ((clock_t) -1);
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return (ru.ru_utime.tv_sec + ru.ru_stime.tv_sec) * hz +
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(ru.ru_utime.tv_usec + ru.ru_stime.tv_usec + 50) / 100 * hz / 10000;
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}
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