FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_pmc.c
1 /*-
2 * Copyright (c) 2003-2008 Joseph Koshy
3 * Copyright (c) 2007 The FreeBSD Foundation
4 * All rights reserved.
5 *
6 * Portions of this software were developed by A. Joseph Koshy under
7 * sponsorship from the FreeBSD Foundation and Google, Inc.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31 #include <sys/cdefs.h>
32 __FBSDID("$FreeBSD: releng/8.1/sys/kern/kern_pmc.c 199583 2009-11-20 15:27:52Z jhb $");
33
34 #include "opt_hwpmc_hooks.h"
35
36 #include <sys/types.h>
37 #include <sys/pmc.h>
38 #include <sys/pmckern.h>
39 #include <sys/smp.h>
40
41 #ifdef HWPMC_HOOKS
42 #define PMC_KERNEL_VERSION PMC_VERSION
43 #else
44 #define PMC_KERNEL_VERSION 0
45 #endif
46
47 const int pmc_kernel_version = PMC_KERNEL_VERSION;
48
49 /* Hook variable. */
50 int (*pmc_hook)(struct thread *td, int function, void *arg) = NULL;
51
52 /* Interrupt handler */
53 int (*pmc_intr)(int cpu, struct trapframe *tf) = NULL;
54
55 /* Bitmask of CPUs requiring servicing at hardclock time */
56 volatile cpumask_t pmc_cpumask;
57
58 /*
59 * A global count of SS mode PMCs. When non-zero, this means that
60 * we have processes that are sampling the system as a whole.
61 */
62 volatile int pmc_ss_count;
63
64 /*
65 * Since PMC(4) may not be loaded in the current kernel, the
66 * convention followed is that a non-NULL value of 'pmc_hook' implies
67 * the presence of this kernel module.
68 *
69 * This requires us to protect 'pmc_hook' with a
70 * shared (sx) lock -- thus making the process of calling into PMC(4)
71 * somewhat more expensive than a simple 'if' check and indirect call.
72 */
73 struct sx pmc_sx;
74
75 static void
76 pmc_init_sx(void)
77 {
78 sx_init_flags(&pmc_sx, "pmc-sx", SX_NOWITNESS);
79 }
80
81 SYSINIT(pmcsx, SI_SUB_LOCK, SI_ORDER_MIDDLE, pmc_init_sx, NULL);
82
83 /*
84 * Helper functions.
85 */
86
87 /*
88 * A note on the CPU numbering scheme used by the hwpmc(4) driver.
89 *
90 * CPUs are denoted using numbers in the range 0..[pmc_cpu_max()-1].
91 * CPUs could be numbered "sparsely" in this range; the predicate
92 * `pmc_cpu_is_present()' is used to test whether a given CPU is
93 * physically present.
94 *
95 * Further, a CPU that is physically present may be administratively
96 * disabled or otherwise unavailable for use by hwpmc(4). The
97 * `pmc_cpu_is_active()' predicate tests for CPU usability. An
98 * "active" CPU participates in thread scheduling and can field
99 * interrupts raised by PMC hardware.
100 *
101 * On systems with hyperthreaded CPUs, multiple logical CPUs may share
102 * PMC hardware resources. For such processors one logical CPU is
103 * denoted as the primary owner of the in-CPU PMC resources. The
104 * pmc_cpu_is_primary() predicate is used to distinguish this primary
105 * CPU from the others.
106 */
107
108 int
109 pmc_cpu_is_active(int cpu)
110 {
111 #ifdef SMP
112 return (pmc_cpu_is_present(cpu) &&
113 (hlt_cpus_mask & (1 << cpu)) == 0);
114 #else
115 return (1);
116 #endif
117 }
118
119 /* Deprecated. */
120 int
121 pmc_cpu_is_disabled(int cpu)
122 {
123 return (!pmc_cpu_is_active(cpu));
124 }
125
126 int
127 pmc_cpu_is_present(int cpu)
128 {
129 #ifdef SMP
130 return (!CPU_ABSENT(cpu));
131 #else
132 return (1);
133 #endif
134 }
135
136 int
137 pmc_cpu_is_primary(int cpu)
138 {
139 #ifdef SMP
140 return ((logical_cpus_mask & (1 << cpu)) == 0);
141 #else
142 return (1);
143 #endif
144 }
145
146
147 /*
148 * Return the maximum CPU number supported by the system. The return
149 * value is used for scaling internal data structures and for runtime
150 * checks.
151 */
152 unsigned int
153 pmc_cpu_max(void)
154 {
155 #ifdef SMP
156 return (mp_maxid+1);
157 #else
158 return (1);
159 #endif
160 }
161
162 #ifdef INVARIANTS
163
164 /*
165 * Return the count of CPUs in the `active' state in the system.
166 */
167 int
168 pmc_cpu_max_active(void)
169 {
170 #ifdef SMP
171 /*
172 * When support for CPU hot-plugging is added to the kernel,
173 * this function would change to return the current number
174 * of "active" CPUs.
175 */
176 return (mp_ncpus);
177 #else
178 return (1);
179 #endif
180 }
181
182 #endif
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