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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>5.3.2. Call Graph Tracing</title><link rel="stylesheet" type="text/css" href="Common_Content/css/default.css" /><link rel="stylesheet" media="print" href="Common_Content/css/print.css" type="text/css" /><meta name="generator" content="publican 2.8" /><meta name="package" content="Systemtap-SystemTap_Beginners_Guide-2.1-en-US-2.1-2" /><link rel="home" href="index.html" title="SystemTap Beginners Guide" /><link rel="up" href="mainsect-profiling.html" title="5.3. Profiling" /><link rel="prev" href="mainsect-profiling.html" title="5.3. Profiling" /><link rel="next" href="threadtimessect.html" title="5.3.3. Determining Time Spent in Kernel and User Space" /></head><body><p id="title"><a class="left" href="http://www.fedoraproject.org"><img src="Common_Content/images/image_left.png" alt="Product Site" /></a><a class="right" href="http://docs.fedoraproject.org"><img src="Common_Content/images/image_right.png" alt="Documentation Site" /></a></p><ul class="docnav"><li class="previous"><a accesskey="p" href="mainsect-profiling.html"><strong>Prev</strong></a></li><li class="next"><a accesskey="n" href="threadtimessect.html"><strong>Next</strong></a></li></ul><div xml:lang="en-US" class="section" id="paracallgraph" lang="en-US"><div class="titlepage"><div><div keep-together.within-column="always"><h3 class="title" id="paracallgraph">5.3.2. Call Graph Tracing</h3></div></div></div><a id="idp5241192" class="indexterm"></a><a id="idp5348520" class="indexterm"></a><a id="idm2005488" class="indexterm"></a><a id="idp8243144" class="indexterm"></a><a id="idm17942920" class="indexterm"></a><a id="idm3772760" class="indexterm"></a><a id="idp7680928" class="indexterm"></a><div class="para">
This section describes how to trace incoming and outgoing function calls.
</div><div class="formalpara" id="scriptcallgraph"><h5 class="formalpara">para-callgraph.stp</h5>
<pre class="programlisting">#! /usr/bin/env stap
function trace(entry_p, extra) {
%( $# > 1 %? if (tid() in trace) %)
printf("%s%s%s %s\n",
thread_indent (entry_p),
(entry_p>0?"->":"<-"),
ppfunc (),
extra)
}
%( $# > 1 %?
global trace
probe $2.call {
trace[tid()] = 1
}
probe $2.return {
delete trace[tid()]
}
%)
probe $1.call { trace(1, $$parms) }
probe $1.return { trace(-1, $$return) }
</pre>
</div><a id="idm2279312" class="indexterm"></a><a id="idm20110120" class="indexterm"></a><a id="idp8399536" class="indexterm"></a><a id="idp5391200" class="indexterm"></a><div class="para">
<a class="xref" href="paracallgraph.html#scriptcallgraph">para-callgraph.stp</a> takes two command-line arguments:
</div><a id="idp37636048" class="indexterm"></a><a id="idp13197080" class="indexterm"></a><a id="idp5421344" class="indexterm"></a><div class="itemizedlist"><ul><li class="listitem"><div class="para">
The function/s whose entry/exit call you'd like to trace (<code class="command">$1</code>).
</div></li><li class="listitem"><div class="para">
A second optional <em class="firstterm">trigger function</em> (<code class="command">$2</code>), 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.
</div></li></ul></div><a id="idp38206408" class="indexterm"></a><a id="idp30482496" class="indexterm"></a><a id="idp8395336" class="indexterm"></a><div class="para">
<a class="xref" href="paracallgraph.html#scriptcallgraph">para-callgraph.stp</a> uses <code class="command">thread_indent()</code>; as such, its output contains the timestamp, process name, and thread ID of <code class="command">$1</code> (i.e. the probe function you are tracing). For more information about <code class="command">thread_indent()</code>, refer to its entry in <a class="xref" href="systemtapscript-handler.html#systemtapscript-functions">SystemTap Functions</a>.
</div><div class="para">
The following example contains an excerpt from the output for <code class="command">stap para-callgraph.stp 'kernel.function("*@fs/*.c")' 'kernel.function("sys_read")'</code>:
</div><div class="example" id="paracallgraphoutput"><h6>Example 5.14. <a class="xref" href="paracallgraph.html#scriptcallgraph">para-callgraph.stp</a> Sample Output</h6><div class="example-contents"><pre class="screen">[...]
267 gnome-terminal(2921): <-do_sync_read return=0xfffffffffffffff5
269 gnome-terminal(2921):<-vfs_read return=0xfffffffffffffff5
0 gnome-terminal(2921):->fput file=0xffff880111eebbc0
2 gnome-terminal(2921):<-fput
0 gnome-terminal(2921):->fget_light fd=0x3 fput_needed=0xffff88010544df54
3 gnome-terminal(2921):<-fget_light return=0xffff8801116ce980
0 gnome-terminal(2921):->vfs_read file=0xffff8801116ce980 buf=0xc86504 count=0x1000 pos=0xffff88010544df48
4 gnome-terminal(2921): ->rw_verify_area read_write=0x0 file=0xffff8801116ce980 ppos=0xffff88010544df48 count=0x1000
7 gnome-terminal(2921): <-rw_verify_area return=0x1000
12 gnome-terminal(2921): ->do_sync_read filp=0xffff8801116ce980 buf=0xc86504 len=0x1000 ppos=0xffff88010544df48
15 gnome-terminal(2921): <-do_sync_read return=0xfffffffffffffff5
18 gnome-terminal(2921):<-vfs_read return=0xfffffffffffffff5
0 gnome-terminal(2921):->fput file=0xffff8801116ce980</pre></div></div><br class="example-break" /></div><ul class="docnav"><li class="previous"><a accesskey="p" href="mainsect-profiling.html"><strong>Prev</strong>5.3. Profiling</a></li><li class="up"><a accesskey="u" href="#"><strong>Up</strong></a></li><li class="home"><a accesskey="h" href="index.html"><strong>Home</strong></a></li><li class="next"><a accesskey="n" href="threadtimessect.html"><strong>Next</strong>5.3.3. Determining Time Spent in Kernel and User ...</a></li></ul></body></html>
