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, 109 insertions, 0 deletions

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);