Merge from projects/counters: counter(9).

  Introduce counter(9) API, that implements fast and raceless counters,
provided (but not limited to) for gathering of statistical data.

See http://lists.freebsd.org/pipermail/freebsd-arch/2013-April/014204.html
for more details.

In collaboration with:	kib
Reviewed by:		luigi
Tested by:		ae, ray
Sponsored by:		Nginx, Inc.

12 files changed, 610 insertions, 0 deletions

diff --git a/sys/amd64/include/counter.h b/sys/amd64/include/counter.h
new file mode 100644
index 0000000..3ed5f76
--- /dev/null
+++ b/sys/amd64/include/counter.h
@@ -0,0 +1,51 @@
+/*-
+ * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
+ * All rights reserved.
+ *
+ * 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 AUTHOR 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 AUTHOR 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.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef __MACHINE_COUNTER_H__
+#define __MACHINE_COUNTER_H__
+
+#include <sys/pcpu.h>
+
+extern struct pcpu __pcpu[1];
+
+#define	counter_enter()	do {} while (0)
+#define	counter_exit()	do {} while (0)
+
+#define	counter_u64_add_protected(c, i)	counter_u64_add(c, i)
+
+static inline void
+counter_u64_add(counter_u64_t c, int64_t inc)
+{
+
+	__asm __volatile("addq\t%1,%%gs:(%0)"
+	    :
+	    : "r" ((char *)c - (char *)&__pcpu[0]), "r" (inc)
+	    : "memory", "cc");
+}
+
+#endif	/* ! __MACHINE_COUNTER_H__ */
diff --git a/sys/arm/include/counter.h b/sys/arm/include/counter.h
new file mode 100644
index 0000000..68f89e2
--- /dev/null
+++ b/sys/arm/include/counter.h
@@ -0,0 +1,54 @@
+/*-
+ * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
+ * All rights reserved.
+ *
+ * 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 AUTHOR 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 AUTHOR 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.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef __MACHINE_COUNTER_H__
+#define __MACHINE_COUNTER_H__
+
+#include <sys/pcpu.h>
+#ifdef INVARIANTS
+#include <sys/proc.h>
+#endif
+
+#define	counter_enter()	critical_enter()
+#define	counter_exit()	critical_exit()
+
+#define	counter_u64_add_protected(c, inc)	do {	\
+	CRITICAL_ASSERT(curthread);			\
+	*(uint64_t *)zpcpu_get(c) += (inc);		\
+} while (0)
+
+static inline void
+counter_u64_add(counter_u64_t c, int64_t inc)
+{
+
+	counter_enter();
+	counter_u64_add_protected(c, inc);
+	counter_exit();
+}
+
+#endif	/* ! __MACHINE_COUNTER_H__ */
diff --git a/sys/conf/files b/sys/conf/files
index c83fb03..95ed2c6 100644
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -2683,6 +2683,7 @@ kern/subr_bus.c			standard
 kern/subr_bus_dma.c		standard
 kern/subr_bufring.c		standard
 kern/subr_clock.c		standard
+kern/subr_counter.c		standard
 kern/subr_devstat.c		standard
 kern/subr_disk.c		standard
 kern/subr_eventhandler.c	standard
diff --git a/sys/i386/include/counter.h b/sys/i386/include/counter.h
new file mode 100644
index 0000000..f45d953
--- /dev/null
+++ b/sys/i386/include/counter.h
@@ -0,0 +1,89 @@
+/*-
+ * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
+ * All rights reserved.
+ *
+ * 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 AUTHOR 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 AUTHOR 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.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef __MACHINE_COUNTER_H__
+#define __MACHINE_COUNTER_H__
+
+#include <sys/pcpu.h>
+#ifdef INVARIANTS
+#include <sys/proc.h>
+#endif
+#include <machine/md_var.h>
+#include <machine/specialreg.h>
+
+#define	counter_enter()	do {				\
+	if ((cpu_feature & CPUID_CX8) == 0)		\
+		critical_enter();			\
+} while (0)
+
+#define	counter_exit()	do {				\
+	if ((cpu_feature & CPUID_CX8) == 0)		\
+		critical_exit();			\
+} while (0)
+
+static inline void
+counter_64_inc_8b(uint64_t *p, int64_t inc)
+{
+
+	__asm __volatile(
+	"movl	%%fs:(%%esi),%%eax\n\t"
+	"movl	%%fs:4(%%esi),%%edx\n"
+"1:\n\t"
+	"movl	%%eax,%%ebx\n\t"
+	"movl	%%edx,%%ecx\n\t"
+	"addl	(%%edi),%%ebx\n\t"
+	"adcl	4(%%edi),%%ecx\n\t"
+	"cmpxchg8b %%fs:(%%esi)\n\t"
+	"jnz	1b"
+	:
+	: "S" (p), "D" (&inc)
+	: "memory", "cc", "eax", "edx", "ebx", "ecx");
+}
+
+#define	counter_u64_add_protected(c, inc)	do {	\
+	if ((cpu_feature & CPUID_CX8) == 0) {		\
+		CRITICAL_ASSERT(curthread);		\
+		*(uint64_t *)zpcpu_get(c) += (inc);	\
+	} else						\
+		counter_64_inc_8b((c), (inc));		\
+} while (0)
+
+static inline void
+counter_u64_add(counter_u64_t c, int64_t inc)
+{
+
+	if ((cpu_feature & CPUID_CX8) == 0) {
+		critical_enter();
+		*(uint64_t *)zpcpu_get(c) += inc;
+		critical_exit();
+	} else {
+		counter_64_inc_8b(c, inc);
+	}
+}
+
+#endif	/* ! __MACHINE_COUNTER_H__ */
diff --git a/sys/ia64/include/counter.h b/sys/ia64/include/counter.h
new file mode 100644
index 0000000..68f89e2
--- /dev/null
+++ b/sys/ia64/include/counter.h
@@ -0,0 +1,54 @@
+/*-
+ * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
+ * All rights reserved.
+ *
+ * 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 AUTHOR 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 AUTHOR 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.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef __MACHINE_COUNTER_H__
+#define __MACHINE_COUNTER_H__
+
+#include <sys/pcpu.h>
+#ifdef INVARIANTS
+#include <sys/proc.h>
+#endif
+
+#define	counter_enter()	critical_enter()
+#define	counter_exit()	critical_exit()
+
+#define	counter_u64_add_protected(c, inc)	do {	\
+	CRITICAL_ASSERT(curthread);			\
+	*(uint64_t *)zpcpu_get(c) += (inc);		\
+} while (0)
+
+static inline void
+counter_u64_add(counter_u64_t c, int64_t inc)
+{
+
+	counter_enter();
+	counter_u64_add_protected(c, inc);
+	counter_exit();
+}
+
+#endif	/* ! __MACHINE_COUNTER_H__ */
diff --git a/sys/kern/subr_counter.c b/sys/kern/subr_counter.c
new file mode 100644
index 0000000..5856cf0
--- /dev/null
+++ b/sys/kern/subr_counter.c
@@ -0,0 +1,109 @@
+/*-
+ * Copyright (c) 2012 Gleb Smirnoff <glebius@FreeBSD.org>
+ * All rights reserved.
+ *
+ * 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 AUTHOR 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 AUTHOR 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 <sys/param.h>
+#include <sys/systm.h>
+#include <sys/counter.h>
+#include <sys/kernel.h>
+#include <sys/smp.h>
+#include <sys/sysctl.h>
+#include <vm/uma.h>
+ 
+static uma_zone_t uint64_pcpu_zone;
+
+void
+counter_u64_zero(counter_u64_t c)
+{
+	int i;
+
+	for (i = 0; i < mp_ncpus; i++)
+		*(uint64_t *)((char *)c + sizeof(struct pcpu) * i) = 0;
+}
+
+uint64_t
+counter_u64_fetch(counter_u64_t c)
+{
+	uint64_t r;
+	int i;
+
+	r = 0;
+	for (i = 0; i < mp_ncpus; i++)
+		r += *(uint64_t *)((char *)c + sizeof(struct pcpu) * i);
+
+	return (r);
+}
+
+counter_u64_t
+counter_u64_alloc(int flags)
+{
+	counter_u64_t r;
+
+	r = uma_zalloc(uint64_pcpu_zone, flags);
+	if (r != NULL)
+		counter_u64_zero(r);
+
+	return (r);
+}
+
+void
+counter_u64_free(counter_u64_t c)
+{
+
+	uma_zfree(uint64_pcpu_zone, c);
+}
+
+int
+sysctl_handle_counter_u64(SYSCTL_HANDLER_ARGS)
+{
+	uint64_t out;
+	int error;
+
+	out = counter_u64_fetch(*(counter_u64_t *)arg1);
+
+	error = SYSCTL_OUT(req, &out, sizeof(uint64_t));
+
+	if (error || !req->newptr)
+		return (error);
+
+	/*
+	 * Any write attempt to a counter zeroes it.
+	 */
+	counter_u64_zero(*(counter_u64_t *)arg1);
+
+	return (0);
+}
+
+static void
+counter_startup(void)
+{
+
+	uint64_pcpu_zone = uma_zcreate("uint64 pcpu", sizeof(uint64_t),
+	    NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_PCPU);
+}
+SYSINIT(counter, SI_SUB_KMEM, SI_ORDER_ANY, counter_startup, NULL);
diff --git a/sys/mips/include/counter.h b/sys/mips/include/counter.h
new file mode 100644
index 0000000..68f89e2
--- /dev/null
+++ b/sys/mips/include/counter.h
@@ -0,0 +1,54 @@
+/*-
+ * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
+ * All rights reserved.
+ *
+ * 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 AUTHOR 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 AUTHOR 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.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef __MACHINE_COUNTER_H__
+#define __MACHINE_COUNTER_H__
+
+#include <sys/pcpu.h>
+#ifdef INVARIANTS
+#include <sys/proc.h>
+#endif
+
+#define	counter_enter()	critical_enter()
+#define	counter_exit()	critical_exit()
+
+#define	counter_u64_add_protected(c, inc)	do {	\
+	CRITICAL_ASSERT(curthread);			\
+	*(uint64_t *)zpcpu_get(c) += (inc);		\
+} while (0)
+
+static inline void
+counter_u64_add(counter_u64_t c, int64_t inc)
+{
+
+	counter_enter();
+	counter_u64_add_protected(c, inc);
+	counter_exit();
+}
+
+#endif	/* ! __MACHINE_COUNTER_H__ */
diff --git a/sys/pc98/include/counter.h b/sys/pc98/include/counter.h
new file mode 100644
index 0000000..7b2bbad
--- /dev/null
+++ b/sys/pc98/include/counter.h
@@ -0,0 +1,6 @@
+/*-
+ * This file is in the public domain.
+ */
+/* $FreeBSD$ */
+
+#include <i386/counter.h>
diff --git a/sys/powerpc/include/counter.h b/sys/powerpc/include/counter.h
new file mode 100644
index 0000000..94a7df6
--- /dev/null
+++ b/sys/powerpc/include/counter.h
@@ -0,0 +1,82 @@
+/*-
+ * Copyright (c) 2012, 2013 Konstantin Belousov <kib@FreeBSD.org>
+ * All rights reserved.
+ *
+ * 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 AUTHOR 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 AUTHOR 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.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef __MACHINE_COUNTER_H__
+#define __MACHINE_COUNTER_H__
+
+#include <sys/pcpu.h>
+#ifdef INVARIANTS
+#include <sys/proc.h>
+#endif
+
+#if defined(AIM) && defined(__powerpc64__)
+
+#define	counter_enter()	do {} while (0)
+#define	counter_exit()	do {} while (0)
+
+#define	counter_u64_add_protected(c, i)	counter_u64_add(c, i)
+
+static inline void
+counter_u64_add(counter_u64_t c, int64_t inc)
+{
+	uint64_t ccpu, old;
+
+	__asm __volatile("\n"
+      "1:\n\t"
+	    "mfsprg	%0, 0\n\t"
+	    "ldarx	%1, %0, %2\n\t"
+	    "add	%1, %1, %3\n\t"
+	    "stdcx.	%1, %0, %2\n\t"
+	    "bne-	1b"
+	    : "=&b" (ccpu), "=&r" (old)
+	    : "r" ((char *)c - (char *)&__pcpu[0]), "r" (inc)
+	    : "cc", "memory");
+}
+
+#else	/* !AIM || !64bit */
+
+#define	counter_enter()	critical_enter()
+#define	counter_exit()	critical_exit()
+
+#define	counter_u64_add_protected(c, inc)	do {	\
+	CRITICAL_ASSERT(curthread);			\
+	*(uint64_t *)zpcpu_get(c) += (inc);		\
+} while (0)
+
+static inline void
+counter_u64_add(counter_u64_t c, int64_t inc)
+{
+
+	counter_enter();
+	counter_u64_add_protected(c, inc);
+	counter_exit();
+}
+
+#endif	/* AIM 64bit */
+
+#endif	/* ! __MACHINE_COUNTER_H__ */
diff --git a/sys/sparc64/include/counter.h b/sys/sparc64/include/counter.h
new file mode 100644
index 0000000..68f89e2
--- /dev/null
+++ b/sys/sparc64/include/counter.h
@@ -0,0 +1,54 @@
+/*-
+ * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
+ * All rights reserved.
+ *
+ * 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 AUTHOR 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 AUTHOR 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.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef __MACHINE_COUNTER_H__
+#define __MACHINE_COUNTER_H__
+
+#include <sys/pcpu.h>
+#ifdef INVARIANTS
+#include <sys/proc.h>
+#endif
+
+#define	counter_enter()	critical_enter()
+#define	counter_exit()	critical_exit()
+
+#define	counter_u64_add_protected(c, inc)	do {	\
+	CRITICAL_ASSERT(curthread);			\
+	*(uint64_t *)zpcpu_get(c) += (inc);		\
+} while (0)
+
+static inline void
+counter_u64_add(counter_u64_t c, int64_t inc)
+{
+
+	counter_enter();
+	counter_u64_add_protected(c, inc);
+	counter_exit();
+}
+
+#endif	/* ! __MACHINE_COUNTER_H__ */
diff --git a/sys/sys/counter.h b/sys/sys/counter.h
new file mode 100644
index 0000000..ee500b5
--- /dev/null
+++ b/sys/sys/counter.h
@@ -0,0 +1,42 @@
+/*-
+ * Copyright (c) 2012 Gleb Smirnoff <glebius@FreeBSD.org>
+ * All rights reserved.
+ *
+ * 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 AUTHOR 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 AUTHOR 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.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef __SYS_COUNTER_H__
+#define __SYS_COUNTER_H__
+
+typedef uint64_t *counter_u64_t;
+
+#include <machine/counter.h>
+
+counter_u64_t	counter_u64_alloc(int);
+void		counter_u64_free(counter_u64_t);
+
+void		counter_u64_zero(counter_u64_t);
+uint64_t	counter_u64_fetch(counter_u64_t);
+
+#endif	/* ! __SYS_COUNTER_H__ */
diff --git a/sys/sys/sysctl.h b/sys/sys/sysctl.h
index e575f22..2fdeed2 100644
--- a/sys/sys/sysctl.h
+++ b/sys/sys/sysctl.h
@@ -184,6 +184,7 @@ int sysctl_handle_long(SYSCTL_HANDLER_ARGS);
 int sysctl_handle_64(SYSCTL_HANDLER_ARGS);
 int sysctl_handle_string(SYSCTL_HANDLER_ARGS);
 int sysctl_handle_opaque(SYSCTL_HANDLER_ARGS);
+int sysctl_handle_counter_u64(SYSCTL_HANDLER_ARGS);
 
 int sysctl_dpcpu_int(SYSCTL_HANDLER_ARGS);
 int sysctl_dpcpu_long(SYSCTL_HANDLER_ARGS);
@@ -379,6 +380,19 @@ SYSCTL_ALLOWED_TYPES(UINT64, uint64_t *a; unsigned long long *b; );
 	    SYSCTL_ADD_ASSERT_TYPE(UINT64, ptr), 0,			\
 	    sysctl_handle_64, "QU", __DESCR(descr))
 
+/* Oid for a 64-bin unsigned counter(9).  The pointer must be non NULL. */
+#define	SYSCTL_COUNTER_U64(parent, nbr, name, access, ptr, val, descr)	\
+	SYSCTL_ASSERT_TYPE(UINT64, ptr, parent, name);			\
+	SYSCTL_OID(parent, nbr, name,					\
+	    CTLTYPE_U64 | CTLFLAG_MPSAFE | (access),			\
+	    ptr, val, sysctl_handle_counter_u64, "QU", descr)
+
+#define	SYSCTL_ADD_COUNTER_U64(ctx, parent, nbr, name, access, ptr, descr)\
+	sysctl_add_oid(ctx, parent, nbr, name,				\
+	    CTLTYPE_U64 | CTLFLAG_MPSAFE | (access),			\
+	    SYSCTL_ADD_ASSERT_TYPE(UINT64, ptr), 0,			\
+	    sysctl_handle_counter_u64, "QU", __DESCR(descr))
+
 /* Oid for an opaque object.  Specified by a pointer and a length. */
 #define SYSCTL_OPAQUE(parent, nbr, name, access, ptr, len, fmt, descr) \
 	SYSCTL_OID(parent, nbr, name, CTLTYPE_OPAQUE|(access), \