217 lines
7.6 KiB
C
217 lines
7.6 KiB
C
/* $NetBSD: kern_microtime.c,v 1.10 2004/06/27 15:21:30 fredb Exp $ */
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/*-
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* Copyright (c) 2001 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Jason R. Thorpe.
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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. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/******************************************************************************
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* *
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* Copyright (c) David L. Mills 1993, 1994 *
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* *
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* Permission to use, copy, modify, and distribute this software and its *
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* documentation for any purpose and without fee is hereby granted, provided *
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* that the above copyright notice appears in all copies and that both the *
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* copyright notice and this permission notice appear in supporting *
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* documentation, and that the name University of Delaware not be used in *
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* advertising or publicity pertaining to distribution of the software *
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* without specific, written prior permission. The University of Delaware *
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* makes no representations about the suitability this software for any *
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* purpose. It is provided "as is" without express or implied warranty. *
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* *
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******************************************************************************/
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#include <sys/cdefs.h> /* RCS ID & Copyright macro defns */
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__KERNEL_RCSID(0, "$NetBSD: kern_microtime.c,v 1.10 2004/06/27 15:21:30 fredb Exp $");
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#include "opt_multiprocessor.h"
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/lock.h>
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#include <machine/cpu.h>
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#include <machine/cpu_counter.h>
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struct timeval cc_microset_time;
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/*
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* Return the best possible estimate of the time in the timeval to which
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* tvp points. The kernel logical time variable is interpolated between
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* ticks by reading the CC to determine the number of cycles since the
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* last processor update, then converting the result to microseconds. In
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* the case of multiprocessor systems, the interpolation is specific to
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* each processor, since each processor has its own CC.
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*/
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void
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cc_microtime(struct timeval *tvp)
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{
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static struct timeval lasttime;
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static struct simplelock microtime_slock = SIMPLELOCK_INITIALIZER;
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struct timeval t;
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struct cpu_info *ci = curcpu();
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int64_t cc, sec, usec;
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int s;
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#ifdef MULTIPROCESSOR
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s = splipi(); /* also blocks IPIs */
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#else
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s = splclock(); /* block clock interrupts */
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#endif
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if (ci->ci_cc_denom != 0) {
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/*
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* Determine the current clock time as the time at last
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* microset() call, plus the CC accumulation since then.
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* This time should lie in the interval between the current
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* master clock time and the time at the next tick, but
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* this code does not explicitly require that in the interest
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* of speed. If something ugly occurs, like a settimeofday()
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* call, the processors may disagree among themselves for not
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* more than the interval between microset() calls. In any
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* case, the following sanity checks will suppress timewarps.
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*/
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simple_lock(µtime_slock);
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t = ci->ci_cc_time;
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cc = cpu_counter32() - ci->ci_cc_cc;
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if (cc < 0)
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cc += 0x100000000LL;
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t.tv_usec += (cc * ci->ci_cc_ms_delta) / ci->ci_cc_denom;
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while (t.tv_usec >= 1000000) {
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t.tv_usec -= 1000000;
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t.tv_sec++;
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}
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} else {
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/*
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* Can't use the CC -- just use the system time.
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*/
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/* XXXSMP: not atomic */
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simple_lock(µtime_slock);
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t = time;
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}
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/*
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* Ordinarily, the current clock time is guaranteed to be later
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* by at least one microsecond than the last time the clock was
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* read. However, this rule applies only if the current time is
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* within one second of the last time. Otherwise, the clock will
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* (shudder) be set backward. The clock adjustment daemon or
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* human equivalent is presumed to be correctly implemented and
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* to set the clock backward only upon unavoidable crisis.
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*/
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sec = lasttime.tv_sec - t.tv_sec;
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usec = lasttime.tv_usec - t.tv_usec;
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if (usec < 0) {
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usec += 1000000;
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sec--;
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}
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if (sec == 0 && usec > 0) {
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t.tv_usec += usec + 1;
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if (t.tv_usec >= 1000000) {
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t.tv_usec -= 1000000;
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t.tv_sec++;
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}
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}
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lasttime = t;
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simple_unlock(µtime_slock);
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splx(s);
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*tvp = t;
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}
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/*
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* This routine is called about once per second directly by the master
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* processor and via an interprocessor interrupt for other processors.
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* It determines the CC frequency of each processor relative to the
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* master clock and the time this determination is made. These values
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* are used by microtime() to interpolate the microseconds between
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* timer interrupts. Note that we assume the kernel variables have
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* been zeroed early in life.
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*/
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void
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cc_microset(struct cpu_info *ci)
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{
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struct timeval t;
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int64_t delta, denom;
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/* Note: Clock interrupts are already blocked. */
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denom = ci->ci_cc_cc;
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t = cc_microset_time; /* XXXSMP: not atomic */
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ci->ci_cc_cc = cpu_counter32();
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if (ci->ci_cc_denom == 0) {
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/*
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* This is our first time here on this CPU. Just
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* start with reasonable initial values.
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*/
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ci->ci_cc_time = t;
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ci->ci_cc_ms_delta = 1000000;
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ci->ci_cc_denom = cpu_frequency(ci);
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return;
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}
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denom = ci->ci_cc_cc - denom;
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if (denom < 0)
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denom += 0x100000000LL;
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delta = (t.tv_sec - ci->ci_cc_time.tv_sec) * 1000000 +
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(t.tv_usec - ci->ci_cc_time.tv_usec);
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ci->ci_cc_time = t;
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/*
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* Make sure it's within .5 to 1.5 seconds -- otherwise,
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* the time is probably be frobbed with by the timekeeper
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* or the human.
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*/
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if (delta > 500000 && delta < 1500000) {
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ci->ci_cc_ms_delta = delta;
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ci->ci_cc_denom = denom;
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#if 0
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printf("cc_microset: delta %" PRId64 ", denom %" PRId64 "\n",
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delta, denom);
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#endif
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} else {
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#if 0
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printf("cc_microset: delta %" PRId64 ", resetting state\n",
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delta);
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#endif
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ci->ci_cc_ms_delta = 1000000;
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ci->ci_cc_denom = cpu_frequency(ci);
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}
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}
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