NetBSD/sys/kern/kern_microtime.c

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/* $NetBSD: kern_microtime.c,v 1.14 2005/01/23 08:39:51 yamt Exp $ */
/*-
* Copyright (c) 2001 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Jason R. Thorpe.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the NetBSD
* Foundation, Inc. and its contributors.
* 4. Neither the name of The NetBSD Foundation nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/******************************************************************************
* *
* Copyright (c) David L. Mills 1993, 1994 *
* *
* Permission to use, copy, modify, and distribute this software and its *
* documentation for any purpose and without fee is hereby granted, provided *
* that the above copyright notice appears in all copies and that both the *
* copyright notice and this permission notice appear in supporting *
* documentation, and that the name University of Delaware not be used in *
* advertising or publicity pertaining to distribution of the software *
* without specific, written prior permission. The University of Delaware *
* makes no representations about the suitability this software for any *
* purpose. It is provided "as is" without express or implied warranty. *
* *
******************************************************************************/
#include <sys/cdefs.h> /* RCS ID & Copyright macro defns */
__KERNEL_RCSID(0, "$NetBSD: kern_microtime.c,v 1.14 2005/01/23 08:39:51 yamt Exp $");
#include "opt_multiprocessor.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <machine/cpu.h>
#include <machine/cpu_counter.h>
/* XXX compat definitions */
#define ci_cc_time ci_cc.cc_time
#define ci_cc_cc ci_cc.cc_cc
#define ci_cc_ms_delta ci_cc.cc_ms_delta
#define ci_cc_denom ci_cc.cc_denom
struct timeval cc_microset_time;
/*
* Return the best possible estimate of the time in the timeval to which
* tvp points. The kernel logical time variable is interpolated between
* ticks by reading the CC to determine the number of cycles since the
* last processor update, then converting the result to microseconds. In
* the case of multiprocessor systems, the interpolation is specific to
* each processor, since each processor has its own CC.
*/
void
cc_microtime(struct timeval *tvp)
{
static struct timeval lasttime;
static struct simplelock microtime_slock = SIMPLELOCK_INITIALIZER;
struct timeval t;
struct cpu_info *ci = curcpu();
int64_t cc, sec, usec;
int s;
#ifdef MULTIPROCESSOR
s = splipi(); /* also blocks IPIs */
#else
s = splclock(); /* block clock interrupts */
#endif
if (ci->ci_cc_denom != 0) {
/*
* Determine the current clock time as the time at last
* microset() call, plus the CC accumulation since then.
* This time should lie in the interval between the current
2004-06-19 22:12:55 +04:00
* master clock time and the time at the next tick, but
* this code does not explicitly require that in the interest
* of speed. If something ugly occurs, like a settimeofday()
* call, the processors may disagree among themselves for not
* more than the interval between microset() calls. In any
* case, the following sanity checks will suppress timewarps.
*/
simple_lock(&microtime_slock);
t = ci->ci_cc_time;
cc = cpu_counter32() - ci->ci_cc_cc;
if (cc < 0)
cc += 0x100000000LL;
t.tv_usec += (cc * ci->ci_cc_ms_delta) / ci->ci_cc_denom;
while (t.tv_usec >= 1000000) {
t.tv_usec -= 1000000;
t.tv_sec++;
}
} else {
/*
* Can't use the CC -- just use the system time.
*/
/* XXXSMP: not atomic */
simple_lock(&microtime_slock);
t = time;
}
/*
* Ordinarily, the current clock time is guaranteed to be later
* by at least one microsecond than the last time the clock was
* read. However, this rule applies only if the current time is
* within one second of the last time. Otherwise, the clock will
* (shudder) be set backward. The clock adjustment daemon or
* human equivalent is presumed to be correctly implemented and
* to set the clock backward only upon unavoidable crisis.
*/
sec = lasttime.tv_sec - t.tv_sec;
usec = lasttime.tv_usec - t.tv_usec;
if (usec < 0) {
usec += 1000000;
sec--;
}
if (sec == 0 && usec > 0) {
t.tv_usec += usec + 1;
if (t.tv_usec >= 1000000) {
t.tv_usec -= 1000000;
t.tv_sec++;
}
}
lasttime = t;
simple_unlock(&microtime_slock);
splx(s);
*tvp = t;
}
/*
* This routine is called about once per second directly by the master
* processor and via an interprocessor interrupt for other processors.
* It determines the CC frequency of each processor relative to the
* master clock and the time this determination is made. These values
* are used by microtime() to interpolate the microseconds between
* timer interrupts. Note that we assume the kernel variables have
* been zeroed early in life.
*/
void
cc_microset(struct cpu_info *ci)
{
struct timeval t;
int64_t delta, denom;
/* Note: Clock interrupts are already blocked. */
denom = ci->ci_cc_cc;
t = cc_microset_time; /* XXXSMP: not atomic */
ci->ci_cc_cc = cpu_counter32();
if (ci->ci_cc_denom == 0) {
/*
* This is our first time here on this CPU. Just
* start with reasonable initial values.
*/
ci->ci_cc_time = t;
ci->ci_cc_ms_delta = 1000000;
ci->ci_cc_denom = cpu_frequency(ci);
return;
}
denom = ci->ci_cc_cc - denom;
if (denom < 0)
denom += 0x100000000LL;
delta = (t.tv_sec - ci->ci_cc_time.tv_sec) * 1000000 +
(t.tv_usec - ci->ci_cc_time.tv_usec);
ci->ci_cc_time = t;
/*
* Make sure it's within .5 to 1.5 seconds -- otherwise,
* the time is probably be frobbed with by the timekeeper
* or the human.
*/
if (delta > 500000 && delta < 1500000) {
ci->ci_cc_ms_delta = delta;
ci->ci_cc_denom = denom;
#if 0
printf("cc_microset[%lu]: delta %" PRId64
", denom %" PRId64 "\n", ci->ci_cpuid, delta, denom);
#endif
} else {
#if 0
printf("cc_microset[%lu]: delta %" PRId64 ", resetting state\n",
(u_long)ci->ci_cpuid, delta);
#endif
ci->ci_cc_ms_delta = 1000000;
ci->ci_cc_denom = cpu_frequency(ci);
}
}