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<?xml version='1.0'?>
<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
]>
<section id="paracallgraph">
<title>Call Graph Tracing</title>
<indexterm>
<primary>script examples</primary>
<secondary>call graph tracing</secondary>
</indexterm>
<indexterm>
<primary>examples of SystemTap scripts</primary>
<secondary>call graph tracing</secondary>
</indexterm>
<indexterm>
<primary>call graph tracing</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<indexterm>
<primary>incoming/outgoing function calls, tracing</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<indexterm>
<primary>function calls (incoming/outgoing), tracing</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<indexterm>
<primary>tracing incoming/outgoing function calls</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<indexterm>
<primary>tracing call graph</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<remark>
WAR STORY: Call graph tracing http://sourceware.org/systemtap/wiki/WSCallGraph?highlight=((WarStories))
</remark>
<remark>
script: http://sourceware.org/systemtap/examples/general/para-callgraph.stp
</remark>
<para>This section describes how to trace incoming and outgoing function calls. </para>
<formalpara id="scriptcallgraph">
<title>para-callgraph-simple.stp</title>
<para>
<programlisting>
<xi:include parse="text" href="extras/para-callgraph-simple.stp" xmlns:xi="http://www.w3.org/2001/XInclude" />
</programlisting>
</para>
</formalpara>
<indexterm>
<primary>script examples</primary>
<secondary>multiple command-line arguments, example of</secondary>
</indexterm>
<indexterm>
<primary>examples of SystemTap scripts</primary>
<secondary>multiple command-line arguments, example of</secondary>
</indexterm>
<indexterm>
<primary>multiple command-line arguments, example of</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<indexterm>
<primary>example of multiple command-line arguments</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<para><xref linkend="scriptcallgraph"/> takes two command-line arguments:</para>
<indexterm>
<primary>script examples</primary>
<secondary>trigger function</secondary>
</indexterm>
<indexterm>
<primary>examples of SystemTap scripts</primary>
<secondary>trigger function</secondary>
</indexterm>
<indexterm>
<primary>trigger function</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<itemizedlist>
<listitem><para>
A <firstterm>trigger function</firstterm> (<command>@1</command>), which
enables or disables tracing on a per-thread basis. Tracing in each thread
will continue as long as the trigger function has not exited yet.
</para></listitem>
<listitem><para>
The kernel function/s whose entry/exit call you'd like to trace
(<command>@2</command>).
</para></listitem>
</itemizedlist>
<remark> please verify previous if correct; i'm particularly interested in finding out how to better describe "trigger function"</remark>
<indexterm>
<primary>script examples</primary>
<secondary>thread_indent(), sample usage</secondary>
</indexterm>
<indexterm>
<primary>examples of SystemTap scripts</primary>
<secondary>thread_indent(), sample usage</secondary>
</indexterm>
<indexterm>
<primary>thread_indent(), sample usage</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<para><xref linkend="scriptcallgraph"/> uses <command>thread_indent()</command>; as such, its output contains the timestamp, process name, and thread ID of <command>@2</command> (i.e. the probe function you are tracing). For more information about <command>thread_indent()</command>, refer to its entry in <xref linkend="systemtapscript-functions"/>.</para>
<para>The following example contains an excerpt from the output for <command>stap para-callgraph.stp sys_read '*@fs/*.c'</command>:</para>
<example id="paracallgraphoutput">
<title><xref linkend="scriptcallgraph"/> Sample Output</title>
<screen>
[...]
0 klogd(1391):->sys_read
14 klogd(1391): ->fget_light
22 klogd(1391): <-fget_light
27 klogd(1391): ->vfs_read
35 klogd(1391): ->rw_verify_area
43 klogd(1391): <-rw_verify_area
49 klogd(1391): ->kmsg_read
0 sendmail(1696):->sys_read
17 sendmail(1696): ->fget_light
26 sendmail(1696): <-fget_light
34 sendmail(1696): ->vfs_read
44 sendmail(1696): ->rw_verify_area
52 sendmail(1696): <-rw_verify_area
58 sendmail(1696): ->proc_file_read
70 sendmail(1696): ->loadavg_read_proc
84 sendmail(1696): ->proc_calc_metrics
92 sendmail(1696): <-proc_calc_metrics
95 sendmail(1696): <-loadavg_read_proc
101 sendmail(1696): <-proc_file_read
106 sendmail(1696): ->dnotify_parent
115 sendmail(1696): <-dnotify_parent
119 sendmail(1696): ->inotify_dentry_parent_queue_event
127 sendmail(1696): <-inotify_dentry_parent_queue_event
133 sendmail(1696): ->inotify_inode_queue_event
141 sendmail(1696): <-inotify_inode_queue_event
146 sendmail(1696): <-vfs_read
151 sendmail(1696):<-sys_read
</screen>
</example>
<!--
function trace(entry_p) {
if(tid() in trace)
printf("%s%s%s\n",thread_indent(entry_p),
(entry_p>0?"->":"<-"),
probefunc())
}
global trace
probe kernel.function(@1).call {
if (execname() == "stapio") next # skip our own helper process
trace[tid()] = 1
trace(1)
}
probe kernel.function(@1).return {
trace(-1)
delete trace[tid()]
}
probe kernel.function(@2).call { trace(1) }
probe kernel.function(@2).return { trace(-1) }
-->
</section>
|
