2 * Copyright (c) 2001 Jake Burkholder.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
30 #include <sys/param.h>
31 #include <sys/kernel.h>
32 #include <sys/systm.h>
34 #include <sys/interrupt.h>
36 #include <sys/sysctl.h>
37 #include <sys/timetc.h>
39 #include <machine/clock.h>
40 #include <machine/cpu.h>
41 #include <machine/frame.h>
42 #include <machine/intr_machdep.h>
43 #include <machine/tick.h>
49 #define TICK_GRACE 10000
51 SYSCTL_NODE(_machdep, OID_AUTO, tick, CTLFLAG_RD, 0, "tick statistics");
53 static int adjust_edges = 0;
54 SYSCTL_INT(_machdep_tick, OID_AUTO, adjust_edges, CTLFLAG_RD, &adjust_edges,
55 0, "total number of times tick interrupts got more than 12.5% behind");
57 static int adjust_excess = 0;
58 SYSCTL_INT(_machdep_tick, OID_AUTO, adjust_excess, CTLFLAG_RD, &adjust_excess,
59 0, "total number of ignored tick interrupts");
61 static int adjust_missed = 0;
62 SYSCTL_INT(_machdep_tick, OID_AUTO, adjust_missed, CTLFLAG_RD, &adjust_missed,
63 0, "total number of missed tick interrupts");
65 static int adjust_ticks = 0;
66 SYSCTL_INT(_machdep_tick, OID_AUTO, adjust_ticks, CTLFLAG_RD, &adjust_ticks,
67 0, "total number of tick interrupts with adjustment");
69 static void tick_hardclock(struct trapframe *);
87 tick_process(struct trapframe *tf)
91 hardclock(TRAPF_USERMODE(tf), TRAPF_PC(tf));
93 hardclock_cpu(TRAPF_USERMODE(tf));
95 profclock(TRAPF_USERMODE(tf), TRAPF_PC(tf));
97 statclock(TRAPF_USERMODE(tf));
101 tick_hardclock(struct trapframe *tf)
103 u_long adj, s, tick, ref;
108 if (curthread->td_critnest > 2 || curthread->td_critnest < 1)
109 panic("nested hardclock %d\n", curthread->td_critnest);
112 * The sequence of reading the TICK register, calculating the value
113 * of the next tick and writing it to the TICK_CMPR register must not
114 * be interrupted, not even by an IPI, otherwise a value that is in
115 * the past could be written in the worst case, causing hardclock to
118 adj = PCPU_GET(tickadj);
119 s = intr_disable_all();
121 wrtickcmpr(tick + tick_increment - adj, 0);
124 ref = PCPU_GET(tickref);
127 while (delta >= tick_increment) {
129 delta -= tick_increment;
130 ref += tick_increment;
136 adjust_missed += count - 1;
137 if (delta > (tick_increment >> 3)) {
140 adj = tick_increment >> 4;
147 PCPU_SET(tickref, ref);
148 PCPU_SET(tickadj, adj);
153 tick_init(u_long clock)
157 tick_MHz = clock / 1000000;
158 tick_increment = clock / hz;
160 * Avoid stopping of hardclock in terms of a lost tick interrupt
161 * by ensuring that the tick period is at least TICK_GRACE ticks.
163 printf("tick_freq=%ld hz=%d tick_increment=%ld\n",
164 tick_freq, hz, tick_increment);
167 if (tick_increment < TICK_GRACE)
168 panic("%s: HZ too high, decrease to at least %ld", __func__,
171 set_cputicker(tick_cputicks, tick_freq, 0);
180 intr_setup(PIL_TICK, tick_hardclock, -1, NULL, NULL);
183 * Try to make the tick interrupts as synchronously as possible on
184 * all CPUs to avoid inaccuracies for migrating processes. Leave out
185 * one tick to make sure that it is not missed.
187 PCPU_SET(tickadj, 0);
188 s = intr_disable_all();
190 base = roundup(base, tick_increment);
191 PCPU_SET(tickref, base);
192 wrtickcmpr(base + tick_increment, 0);