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

     /*-
      * Copyright (c) 2003-2008 Joseph Koshy
      * Copyright (c) 2007 The FreeBSD Foundation
      * All rights reserved.
      *
      * Portions of this software were developed by A. Joseph Koshy under
      * sponsorship from the FreeBSD Foundation and Google, Inc.
      *
      * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include "opt_hwpmc_hooks.h"
    
    #include <sys/types.h>
    #include <sys/ctype.h>
    #include <sys/param.h>
    #include <sys/malloc.h>
    #include <sys/kernel.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/pmc.h>
    #include <sys/pmckern.h>
    #include <sys/smp.h>
    #include <sys/sysctl.h>
    #include <sys/systm.h>
    
    #ifdef  HWPMC_HOOKS
    FEATURE(hwpmc_hooks, "Kernel support for HW PMC");
    #define PMC_KERNEL_VERSION      PMC_VERSION
    #else
    #define PMC_KERNEL_VERSION      0
    #endif
    
    MALLOC_DECLARE(M_PMCHOOKS);
    MALLOC_DEFINE(M_PMCHOOKS, "pmchooks", "Memory space for PMC hooks");
    
    const int pmc_kernel_version = PMC_KERNEL_VERSION;
    
    /* Hook variable. */
    int (*pmc_hook)(struct thread *td, int function, void *arg) = NULL;
    
    /* Interrupt handler */
    int (*pmc_intr)(int cpu, struct trapframe *tf) = NULL;
    
    /* Bitmask of CPUs requiring servicing at hardclock time */
    volatile cpuset_t pmc_cpumask;
    
    /*
     * A global count of SS mode PMCs.  When non-zero, this means that
     * we have processes that are sampling the system as a whole.
     */
    volatile int pmc_ss_count;
    
    /*
     * Since PMC(4) may not be loaded in the current kernel, the
     * convention followed is that a non-NULL value of 'pmc_hook' implies
     * the presence of this kernel module.
     *
     * This requires us to protect 'pmc_hook' with a
     * shared (sx) lock -- thus making the process of calling into PMC(4)
     * somewhat more expensive than a simple 'if' check and indirect call.
     */
    struct sx pmc_sx;
    
    /*
     * PMC Soft per cpu trapframe.
     */
    struct trapframe pmc_tf[MAXCPU];
    
    /*
     * PMC Soft use a global table to store registered events.
     */
    
    SYSCTL_NODE(_kern, OID_AUTO, hwpmc, CTLFLAG_RW, 0, "HWPMC parameters");
    
    static int pmc_softevents = 16;
    TUNABLE_INT(PMC_SYSCTL_NAME_PREFIX "softevents", &pmc_softevents);
   SYSCTL_INT(_kern_hwpmc, OID_AUTO, softevents, CTLFLAG_TUN|CTLFLAG_RD,
       &pmc_softevents, 0, "maximum number of soft events");
   
   struct mtx pmc_softs_mtx;
   int pmc_softs_count;
   struct pmc_soft **pmc_softs;
   
   MTX_SYSINIT(pmc_soft_mtx, &pmc_softs_mtx, "pmc-softs", MTX_SPIN);
   
   static void
   pmc_init_sx(void)
   {
           sx_init_flags(&pmc_sx, "pmc-sx", SX_NOWITNESS);
   }
   
   SYSINIT(pmcsx, SI_SUB_LOCK, SI_ORDER_MIDDLE, pmc_init_sx, NULL);
   
   /*
    * Helper functions.
    */
   
   /*
    * A note on the CPU numbering scheme used by the hwpmc(4) driver.
    *
    * CPUs are denoted using numbers in the range 0..[pmc_cpu_max()-1].
    * CPUs could be numbered "sparsely" in this range; the predicate
    * `pmc_cpu_is_present()' is used to test whether a given CPU is
    * physically present.
    *
    * Further, a CPU that is physically present may be administratively
    * disabled or otherwise unavailable for use by hwpmc(4).  The
    * `pmc_cpu_is_active()' predicate tests for CPU usability.  An
    * "active" CPU participates in thread scheduling and can field
    * interrupts raised by PMC hardware.
    *
    * On systems with hyperthreaded CPUs, multiple logical CPUs may share
    * PMC hardware resources.  For such processors one logical CPU is
    * denoted as the primary owner of the in-CPU PMC resources. The
    * pmc_cpu_is_primary() predicate is used to distinguish this primary
    * CPU from the others.
    */
   
   int
   pmc_cpu_is_active(int cpu)
   {
   #ifdef  SMP
           return (pmc_cpu_is_present(cpu) &&
               !CPU_ISSET(cpu, &hlt_cpus_mask));
   #else
           return (1);
   #endif
   }
   
   /* Deprecated. */
   int
   pmc_cpu_is_disabled(int cpu)
   {
           return (!pmc_cpu_is_active(cpu));
   }
   
   int
   pmc_cpu_is_present(int cpu)
   {
   #ifdef  SMP
           return (!CPU_ABSENT(cpu));
   #else
           return (1);
   #endif
   }
   
   int
   pmc_cpu_is_primary(int cpu)
   {
   #ifdef  SMP
           return (!CPU_ISSET(cpu, &logical_cpus_mask));
   #else
           return (1);
   #endif
   }
   
   
   /*
    * Return the maximum CPU number supported by the system.  The return
    * value is used for scaling internal data structures and for runtime
    * checks.
    */
   unsigned int
   pmc_cpu_max(void)
   {
   #ifdef  SMP
           return (mp_maxid+1);
   #else
           return (1);
   #endif
   }
   
   #ifdef  INVARIANTS
   
   /*
    * Return the count of CPUs in the `active' state in the system.
    */
   int
   pmc_cpu_max_active(void)
   {
   #ifdef  SMP
           /*
            * When support for CPU hot-plugging is added to the kernel,
            * this function would change to return the current number
            * of "active" CPUs.
            */
           return (mp_ncpus);
   #else
           return (1);
   #endif
   }
   
   #endif
   
   /*
    * Cleanup event name:
    * - remove duplicate '_'
    * - all uppercase
    */
   static void
   pmc_soft_namecleanup(char *name)
   {
           char *p, *q;
   
           p = q = name;
   
           for ( ; *p == '_' ; p++)
                   ;
           for ( ; *p ; p++) {
                   if (*p == '_' && (*(p + 1) == '_' || *(p + 1) == '\0'))
                           continue;
                   else
                           *q++ = toupper(*p);
           }
           *q = '\0';
   }
   
   void
   pmc_soft_ev_register(struct pmc_soft *ps)
   {
           static int warned = 0;
           int n;
   
           ps->ps_running  = 0;
           ps->ps_ev.pm_ev_code = 0; /* invalid */
           pmc_soft_namecleanup(ps->ps_ev.pm_ev_name);
   
           mtx_lock_spin(&pmc_softs_mtx);
   
           if (pmc_softs_count >= pmc_softevents) {
                   /*
                    * XXX Reusing events can enter a race condition where
                    * new allocated event will be used as an old one.
                    */
                   for (n = 0; n < pmc_softevents; n++)
                           if (pmc_softs[n] == NULL)
                                   break;
                   if (n == pmc_softevents) {
                           mtx_unlock_spin(&pmc_softs_mtx);
                           if (!warned) {
                                   printf("hwpmc: too many soft events, "
                                       "increase kern.hwpmc.softevents tunable\n");
                                   warned = 1;
                           }
                           return;
                   }
   
                   ps->ps_ev.pm_ev_code = PMC_EV_SOFT_FIRST + n;
                   pmc_softs[n] = ps;
           } else {
                   ps->ps_ev.pm_ev_code = PMC_EV_SOFT_FIRST + pmc_softs_count;
                   pmc_softs[pmc_softs_count++] = ps;
           }
   
           mtx_unlock_spin(&pmc_softs_mtx);
   }
   
   void
   pmc_soft_ev_deregister(struct pmc_soft *ps)
   {
   
           KASSERT(ps != NULL, ("pmc_soft_deregister: called with NULL"));
   
           mtx_lock_spin(&pmc_softs_mtx);
   
           if (ps->ps_ev.pm_ev_code != 0 &&
               (ps->ps_ev.pm_ev_code - PMC_EV_SOFT_FIRST) < pmc_softevents) {
                   KASSERT(ps->ps_ev.pm_ev_code >= PMC_EV_SOFT_FIRST &&
                       ps->ps_ev.pm_ev_code <= PMC_EV_SOFT_LAST,
                       ("pmc_soft_deregister: invalid event value"));
                   pmc_softs[ps->ps_ev.pm_ev_code - PMC_EV_SOFT_FIRST] = NULL;
           }
   
           mtx_unlock_spin(&pmc_softs_mtx);
   }
   
   struct pmc_soft *
   pmc_soft_ev_acquire(enum pmc_event ev)
   {
           struct pmc_soft *ps;
   
           if (ev == 0 || (ev - PMC_EV_SOFT_FIRST) >= pmc_softevents)
                   return NULL;
   
           KASSERT(ev >= PMC_EV_SOFT_FIRST &&
               ev <= PMC_EV_SOFT_LAST,
               ("event out of range"));
   
           mtx_lock_spin(&pmc_softs_mtx);
   
           ps = pmc_softs[ev - PMC_EV_SOFT_FIRST];
           if (ps == NULL)
                   mtx_unlock_spin(&pmc_softs_mtx);
   
           return ps;
   }
   
   void
   pmc_soft_ev_release(struct pmc_soft *ps)
   {
   
           mtx_unlock_spin(&pmc_softs_mtx);
   }
   
   /*
    *  Initialise hwpmc.
    */
   static void
   init_hwpmc(void *dummy __unused)
   {
           if (pmc_softevents <= 0 ||
               pmc_softevents > PMC_EV_DYN_COUNT) {
                   (void) printf("hwpmc: tunable \"softevents\"=%d out of "
                       "range.\n", pmc_softevents);
                   pmc_softevents = PMC_EV_DYN_COUNT;
           }
           pmc_softs = malloc(pmc_softevents * sizeof(struct pmc_soft *), M_PMCHOOKS, M_NOWAIT|M_ZERO);
           KASSERT(pmc_softs != NULL, ("cannot allocate soft events table"));
   }
   
   SYSINIT(hwpmc, SI_SUB_KDTRACE, SI_ORDER_FIRST, init_hwpmc, NULL);
   

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