kern_pmc.c

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/*-
 * 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("$BSDSUniX$");

#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);