Add a DTrace script to show the frequency and latency of NFS client calls.

Submitted by:	rwatson

share/dtrace/nfsclienttime

@@ -0,0 +1,74 @@
+#!/bin/sh
+#
+# Copyright (c) 2012 Robert N. M. Watson
+# All rights reserved.
+#
+# This software was developed at the University of Cambridge Computer
+# Laboratory with support from a grant from 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 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.
+#
+# $FreeBSD$
+#
+# This script measures all time spent waiting on RPC replies for each
+# system call, and then generates a histogram of those times sorted by
+# system call name.
+#
+# Currently only supports NFSv3
+#
+# Usage: nfsclienttime
+#
+# Press Ctrl-C to exit and display statistics.
+#
+
+/usr/sbin/dtrace -n '
+#pragma D option quiet
+
+dtrace:::BEGIN
+{
+	printf("Collecting data...press Ctrl-C to exit.\n");
+}
+
+syscall:::entry
+{
+
+        self->count = 0;
+}
+
+nfsclient:nfs3::start
+{
+
+        self->timestamp = timestamp;
+}
+
+nfsclient:nfs3::done
+{
+
+        self->count += (timestamp - self->timestamp);
+}
+
+syscall:::return
+/self->count != 0/  {
+
+        @syscalls[probefunc] = quantize(self->count);
+}
+'