kern_pmc.c revision 222813 
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: head/sys/kern/kern_pmc.c 222813 2011-06-07 08:46:13Z attilio $");
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#include <sys/sysctl.h>
41
42#ifdef	HWPMC_HOOKS
43FEATURE(hwpmc_hooks, "Kernel support for HW PMC");
44#define	PMC_KERNEL_VERSION	PMC_VERSION
45#else
46#define	PMC_KERNEL_VERSION	0
47#endif
48
49const int pmc_kernel_version = PMC_KERNEL_VERSION;
50
51/* Hook variable. */
52int (*pmc_hook)(struct thread *td, int function, void *arg) = NULL;
53
54/* Interrupt handler */
55int (*pmc_intr)(int cpu, struct trapframe *tf) = NULL;
56
57/* Bitmask of CPUs requiring servicing at hardclock time */
58volatile cpuset_t pmc_cpumask;
59
60/*
61 * A global count of SS mode PMCs.  When non-zero, this means that
62 * we have processes that are sampling the system as a whole.
63 */
64volatile int pmc_ss_count;
65
66/*
67 * Since PMC(4) may not be loaded in the current kernel, the
68 * convention followed is that a non-NULL value of 'pmc_hook' implies
69 * the presence of this kernel module.
70 *
71 * This requires us to protect 'pmc_hook' with a
72 * shared (sx) lock -- thus making the process of calling into PMC(4)
73 * somewhat more expensive than a simple 'if' check and indirect call.
74 */
75struct sx pmc_sx;
76
77static void
78pmc_init_sx(void)
79{
80	sx_init_flags(&pmc_sx, "pmc-sx", SX_NOWITNESS);
81}
82
83SYSINIT(pmcsx, SI_SUB_LOCK, SI_ORDER_MIDDLE, pmc_init_sx, NULL);
84
85/*
86 * Helper functions.
87 */
88
89/*
90 * A note on the CPU numbering scheme used by the hwpmc(4) driver.
91 *
92 * CPUs are denoted using numbers in the range 0..[pmc_cpu_max()-1].
93 * CPUs could be numbered "sparsely" in this range; the predicate
94 * `pmc_cpu_is_present()' is used to test whether a given CPU is
95 * physically present.
96 *
97 * Further, a CPU that is physically present may be administratively
98 * disabled or otherwise unavailable for use by hwpmc(4).  The
99 * `pmc_cpu_is_active()' predicate tests for CPU usability.  An
100 * "active" CPU participates in thread scheduling and can field
101 * interrupts raised by PMC hardware.
102 *
103 * On systems with hyperthreaded CPUs, multiple logical CPUs may share
104 * PMC hardware resources.  For such processors one logical CPU is
105 * denoted as the primary owner of the in-CPU PMC resources. The
106 * pmc_cpu_is_primary() predicate is used to distinguish this primary
107 * CPU from the others.
108 */
109
110int
111pmc_cpu_is_active(int cpu)
112{
113#ifdef	SMP
114	return (pmc_cpu_is_present(cpu) &&
115	    !CPU_ISSET(cpu, &hlt_cpus_mask));
116#else
117	return (1);
118#endif
119}
120
121/* Deprecated. */
122int
123pmc_cpu_is_disabled(int cpu)
124{
125	return (!pmc_cpu_is_active(cpu));
126}
127
128int
129pmc_cpu_is_present(int cpu)
130{
131#ifdef	SMP
132	return (!CPU_ABSENT(cpu));
133#else
134	return (1);
135#endif
136}
137
138int
139pmc_cpu_is_primary(int cpu)
140{
141#ifdef	SMP
142	return (!CPU_ISSET(cpu, &logical_cpus_mask));
143#else
144	return (1);
145#endif
146}
147
148
149/*
150 * Return the maximum CPU number supported by the system.  The return
151 * value is used for scaling internal data structures and for runtime
152 * checks.
153 */
154unsigned int
155pmc_cpu_max(void)
156{
157#ifdef	SMP
158	return (mp_maxid+1);
159#else
160	return (1);
161#endif
162}
163
164#ifdef	INVARIANTS
165
166/*
167 * Return the count of CPUs in the `active' state in the system.
168 */
169int
170pmc_cpu_max_active(void)
171{
172#ifdef	SMP
173	/*
174	 * When support for CPU hot-plugging is added to the kernel,
175	 * this function would change to return the current number
176	 * of "active" CPUs.
177	 */
178	return (mp_ncpus);
179#else
180	return (1);
181#endif
182}
183
184#endif
185