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freebsd/sys/kern/kern_pmc.c
Fabien Thomas f5f9340b98 Add software PMC support.
New kernel events can be added at various location for sampling or counting.
This will for example allow easy system profiling whatever the processor is
with known tools like pmcstat(8).

Simultaneous usage of software PMC and hardware PMC is possible, for example
looking at the lock acquire failure, page fault while sampling on
instructions.

Sponsored by: NETASQ
MFC after:	1 month
2012-03-28 20:58:30 +00:00

346 lines
8.3 KiB
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);