/* $NetBSD: kern_microtime.c,v 1.6 2004/06/19 18:12:55 fredb 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 /* RCS ID & Copyright macro defns */ __KERNEL_RCSID(0, "$NetBSD: kern_microtime.c,v 1.6 2004/06/19 18:12:55 fredb Exp $"); #include "opt_multiprocessor.h" #include #include #include #include #include #include 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 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 * 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. */ t = ci->ci_cc_time; usec = cpu_counter32() - ci->ci_cc_cc; if (usec < 0) usec += 0x100000000LL; t.tv_usec += (usec * 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 */ 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. */ simple_lock(µtime_slock); 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(µtime_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: delta %" PRId64 ", denom %" PRId64 "\n", delta, denom); #endif } else { #if 0 printf("cc_microset: delta %" PRId64 ", resetting state\n", delta); #endif ci->ci_cc_ms_delta = 1000000; ci->ci_cc_denom = cpu_frequency(ci); } }