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.

1 files changed, 89 insertions, 0 deletions

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__ */