The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_pmc.c

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    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/7.4/sys/kern/kern_pmc.c 193634 2009-06-07 10:00:35Z fabient $");
   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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