1 /* $NetBSD: kern_microtime.c,v 1.14 2005/01/23 08:39:51 yamt Exp $ */
2
3 /*-
4 * Copyright (c) 2001 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jason R. Thorpe.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 * must display the following acknowledgement:
20 * This product includes software developed by the NetBSD
21 * Foundation, Inc. and its contributors.
22 * 4. Neither the name of The NetBSD Foundation nor the names of its
23 * contributors may be used to endorse or promote products derived
24 * from this software without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
36 * POSSIBILITY OF SUCH DAMAGE.
37 */
38
39 /******************************************************************************
40 * *
41 * Copyright (c) David L. Mills 1993, 1994 *
42 * *
43 * Permission to use, copy, modify, and distribute this software and its *
44 * documentation for any purpose and without fee is hereby granted, provided *
45 * that the above copyright notice appears in all copies and that both the *
46 * copyright notice and this permission notice appear in supporting *
47 * documentation, and that the name University of Delaware not be used in *
48 * advertising or publicity pertaining to distribution of the software *
49 * without specific, written prior permission. The University of Delaware *
50 * makes no representations about the suitability this software for any *
51 * purpose. It is provided "as is" without express or implied warranty. *
52 * *
53 ******************************************************************************/
54
55 #include <sys/cdefs.h> /* RCS ID & Copyright macro defns */
56
57 __KERNEL_RCSID(0, "$NetBSD: kern_microtime.c,v 1.14 2005/01/23 08:39:51 yamt Exp $");
58
59 #include "opt_multiprocessor.h"
60
61 #include <sys/param.h>
62 #include <sys/systm.h>
63 #include <sys/kernel.h>
64 #include <sys/lock.h>
65
66 #include <machine/cpu.h>
67 #include <machine/cpu_counter.h>
68
69 /* XXX compat definitions */
70 #define ci_cc_time ci_cc.cc_time
71 #define ci_cc_cc ci_cc.cc_cc
72 #define ci_cc_ms_delta ci_cc.cc_ms_delta
73 #define ci_cc_denom ci_cc.cc_denom
74
75 struct timeval cc_microset_time;
76
77 /*
78 * Return the best possible estimate of the time in the timeval to which
79 * tvp points. The kernel logical time variable is interpolated between
80 * ticks by reading the CC to determine the number of cycles since the
81 * last processor update, then converting the result to microseconds. In
82 * the case of multiprocessor systems, the interpolation is specific to
83 * each processor, since each processor has its own CC.
84 */
85 void
86 cc_microtime(struct timeval *tvp)
87 {
88 static struct timeval lasttime;
89 static struct simplelock microtime_slock = SIMPLELOCK_INITIALIZER;
90 struct timeval t;
91 struct cpu_info *ci = curcpu();
92 int64_t cc, sec, usec;
93 int s;
94
95 #ifdef MULTIPROCESSOR
96 s = splipi(); /* also blocks IPIs */
97 #else
98 s = splclock(); /* block clock interrupts */
99 #endif
100
101 if (ci->ci_cc_denom != 0) {
102 /*
103 * Determine the current clock time as the time at last
104 * microset() call, plus the CC accumulation since then.
105 * This time should lie in the interval between the current
106 * master clock time and the time at the next tick, but
107 * this code does not explicitly require that in the interest
108 * of speed. If something ugly occurs, like a settimeofday()
109 * call, the processors may disagree among themselves for not
110 * more than the interval between microset() calls. In any
111 * case, the following sanity checks will suppress timewarps.
112 */
113 simple_lock(µtime_slock);
114 t = ci->ci_cc_time;
115 cc = cpu_counter32() - ci->ci_cc_cc;
116 if (cc < 0)
117 cc += 0x100000000LL;
118 t.tv_usec += (cc * ci->ci_cc_ms_delta) / ci->ci_cc_denom;
119 while (t.tv_usec >= 1000000) {
120 t.tv_usec -= 1000000;
121 t.tv_sec++;
122 }
123 } else {
124 /*
125 * Can't use the CC -- just use the system time.
126 */
127 /* XXXSMP: not atomic */
128 simple_lock(µtime_slock);
129 t = time;
130 }
131
132 /*
133 * Ordinarily, the current clock time is guaranteed to be later
134 * by at least one microsecond than the last time the clock was
135 * read. However, this rule applies only if the current time is
136 * within one second of the last time. Otherwise, the clock will
137 * (shudder) be set backward. The clock adjustment daemon or
138 * human equivalent is presumed to be correctly implemented and
139 * to set the clock backward only upon unavoidable crisis.
140 */
141 sec = lasttime.tv_sec - t.tv_sec;
142 usec = lasttime.tv_usec - t.tv_usec;
143 if (usec < 0) {
144 usec += 1000000;
145 sec--;
146 }
147 if (sec == 0 && usec > 0) {
148 t.tv_usec += usec + 1;
149 if (t.tv_usec >= 1000000) {
150 t.tv_usec -= 1000000;
151 t.tv_sec++;
152 }
153 }
154 lasttime = t;
155 simple_unlock(µtime_slock);
156
157 splx(s);
158
159 *tvp = t;
160 }
161
162 /*
163 * This routine is called about once per second directly by the master
164 * processor and via an interprocessor interrupt for other processors.
165 * It determines the CC frequency of each processor relative to the
166 * master clock and the time this determination is made. These values
167 * are used by microtime() to interpolate the microseconds between
168 * timer interrupts. Note that we assume the kernel variables have
169 * been zeroed early in life.
170 */
171 void
172 cc_microset(struct cpu_info *ci)
173 {
174 struct timeval t;
175 int64_t delta, denom;
176
177 /* Note: Clock interrupts are already blocked. */
178
179 denom = ci->ci_cc_cc;
180 t = cc_microset_time; /* XXXSMP: not atomic */
181 ci->ci_cc_cc = cpu_counter32();
182
183 if (ci->ci_cc_denom == 0) {
184 /*
185 * This is our first time here on this CPU. Just
186 * start with reasonable initial values.
187 */
188 ci->ci_cc_time = t;
189 ci->ci_cc_ms_delta = 1000000;
190 ci->ci_cc_denom = cpu_frequency(ci);
191 return;
192 }
193
194 denom = ci->ci_cc_cc - denom;
195 if (denom < 0)
196 denom += 0x100000000LL;
197
198 delta = (t.tv_sec - ci->ci_cc_time.tv_sec) * 1000000 +
199 (t.tv_usec - ci->ci_cc_time.tv_usec);
200
201 ci->ci_cc_time = t;
202 /*
203 * Make sure it's within .5 to 1.5 seconds -- otherwise,
204 * the time is probably be frobbed with by the timekeeper
205 * or the human.
206 */
207 if (delta > 500000 && delta < 1500000) {
208 ci->ci_cc_ms_delta = delta;
209 ci->ci_cc_denom = denom;
210 #if 0
211 printf("cc_microset[%lu]: delta %" PRId64
212 ", denom %" PRId64 "\n", ci->ci_cpuid, delta, denom);
213 #endif
214 } else {
215 #if 0
216 printf("cc_microset[%lu]: delta %" PRId64 ", resetting state\n",
217 (u_long)ci->ci_cpuid, delta);
218 #endif
219 ci->ci_cc_ms_delta = 1000000;
220 ci->ci_cc_denom = cpu_frequency(ci);
221 }
222 }
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