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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>4.3.5. Tracking Most Frequently Used System Calls</title><link rel="stylesheet" href="./Common_Content/css/default.css" type="text/css" /><meta name="generator" content="publican 1.6" /><meta name="package" content="Systemtap-SystemTap_Beginners_Guide-1.0-en-US-2.0-2" /><link rel="home" href="index.html" title="SystemTap Beginners Guide" /><link rel="up" href="mainsect-profiling.html" title="4.3. Profiling" /><link rel="prev" href="timeoutssect.html" title="4.3.4. Monitoring Polling Applications" /><link rel="next" href="syscallsbyprocpidsect.html" title="4.3.6. Tracking System Call Volume Per Process" /></head><body class=""><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="timeoutssect.html"><strong>Prev</strong></a></li><li class="next"><a accesskey="n" href="syscallsbyprocpidsect.html"><strong>Next</strong></a></li></ul><div xml:lang="en-US" class="section" title="4.3.5. Tracking Most Frequently Used System Calls" lang="en-US"><div class="titlepage"><div><div><h3 class="title" id="topsyssect">4.3.5. Tracking Most Frequently Used System Calls</h3></div></div></div><a id="id3081189" class="indexterm"></a><a id="id3422695" class="indexterm"></a><a id="id2971483" class="indexterm"></a><a id="id2764578" class="indexterm"></a><div class="para">
<a class="xref" href="timeoutssect.html#timeouts" title="timeout.stp">timeout.stp</a> from <a class="xref" href="timeoutssect.html" title="4.3.4. Monitoring Polling Applications">Section 4.3.4, “Monitoring Polling Applications”</a> helps you identify which applications are polling by pointing out which ones used the following system calls most frequently:
</div><div class="itemizedlist"><ul><li class="listitem"><div class="para">
<code class="command">poll</code>
</div></li><li class="listitem"><div class="para">
<code class="command">select</code>
</div></li><li class="listitem"><div class="para">
<code class="command">epoll</code>
</div></li><li class="listitem"><div class="para">
<code class="command">itimer</code>
</div></li><li class="listitem"><div class="para">
<code class="command">futex</code>
</div></li><li class="listitem"><div class="para">
<code class="command">nanosleep</code>
</div></li><li class="listitem"><div class="para">
<code class="command">signal</code>
</div></li></ul></div><div class="para">
However, in some systems, a different system call might be responsible for excessive polling. If you suspect that a polling application might is using a different system call to poll, you need to identify first the top system calls used by the system. To do this, use <a class="xref" href="topsyssect.html#topsys" title="topsys.stp">topsys.stp</a>.
</div><div class="formalpara"><h5 class="formalpara" id="topsys">topsys.stp</h5>
<pre class="programlisting">
#! /usr/bin/env stap
#
# This script continuously lists the top 20 systemcalls in the interval
# 5 seconds
#
global syscalls_count
probe syscall.* {
syscalls_count[name]++
}
function print_systop () {
printf ("%25s %10s\n", "SYSCALL", "COUNT")
foreach (syscall in syscalls_count- limit 20) {
printf("%25s %10d\n", syscall, syscalls_count[syscall])
}
delete syscalls_count
}
probe timer.s(5) {
print_systop ()
printf("--------------------------------------------------------------\n")
}
</pre>
</div><div class="para">
<a class="xref" href="topsyssect.html#topsys" title="topsys.stp">topsys.stp</a> lists the top 20 system calls used by the system per 5-second interval. It also lists how many times each system call was used during that period. Refer to <a class="xref" href="topsyssect.html#topsysoutput" title="Example 4.17. topsys.stp Sample Output">Example 4.17, “topsys.stp Sample Output”</a> for a sample output.
</div><a id="id2767085" class="indexterm"></a><a id="id2994028" class="indexterm"></a><a id="id2715971" class="indexterm"></a><div class="example" id="topsysoutput"><div class="example-contents"><pre class="screen">
--------------------------------------------------------------
SYSCALL COUNT
gettimeofday 1857
read 1821
ioctl 1568
poll 1033
close 638
open 503
select 455
write 391
writev 335
futex 303
recvmsg 251
socket 137
clock_gettime 124
rt_sigprocmask 121
sendto 120
setitimer 106
stat 90
time 81
sigreturn 72
fstat 66
--------------------------------------------------------------
</pre></div><h6>Example 4.17. <a class="xref" href="topsyssect.html#topsys" title="topsys.stp">topsys.stp</a> Sample Output</h6></div><br class="example-break" /></div><ul class="docnav"><li class="previous"><a accesskey="p" href="timeoutssect.html"><strong>Prev</strong>4.3.4. Monitoring Polling Applications</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="syscallsbyprocpidsect.html"><strong>Next</strong>4.3.6. Tracking System Call Volume Per Process</a></li></ul></body></html>
