Add a script that traces NFS attribute cache accesses.

Submitted by:	rwatson
MFC after:	2 weeks

share/dtrace/nfsattrstats

@@ -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 creates a trace of NFS RPCs, NFS attribute cache
+# activity, and NFS access cache activity, along with the system call
+# that instigated the activity. Notice that NFS events may happen
+# outside of the context of a system call, most likely due to the VM
+# system paging from NFS, in which case the system call name is
+# reported as "-"
+
+/usr/sbin/dtrace -n '
+#pragma D option quiet
+
+dtrace:::BEGIN
+{
+	printf("probe\targ0\texecutable\tsyscall\n");
+}
+
+syscall:::entry
+{
+
+        self->syscallname = probefunc;
+}
+
+syscall:::return
+{
+
+        self->syscallname = "";
+}
+
+nfsclient:::
+/self->syscallname != 0 && self->syscallname != ""/
+{
+
+    printf("%s\t%s\t%s\t%s\n", probemod, stringof(arg0), execname, 
+	    self->syscallname);
+}
+
+nfsclient:::
+/self->syscallname == 0 || self->syscallname == ""/
+{
+
+    printf("%s\t%s\t%s\t%s\n", probemod, stringof(arg0), execname, 
+	    self->syscallname);
+}
+'