1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 | <?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title xmlns:d="http://docbook.org/ns/docbook">5.2.4. I/O Monitoring (By Device)</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 xmlns:d="http://docbook.org/ns/docbook" name="generator" content="publican v4.0.0" /><meta xmlns:d="http://docbook.org/ns/docbook" name="package" content="SystemTap-SystemTap_Beginners_Guide-2.6-en-US-2.0-1" /><link rel="home" href="index.html" title="SystemTap Beginners Guide" /><link rel="up" href="mainsect-disk.html" title="5.2. Disk" /><link rel="prev" href="traceiosect.html" title="5.2.3. Track Cumulative IO" /><link rel="next" href="inodewatchsect.html" title="5.2.5. Monitoring Reads and Writes to a File" /></head><body><p id="title"><a class="left" href="https://fedorahosted.org/publican"><img alt="Product Site" src="Common_Content/images//image_left.png" /></a><a class="right" href="https://fedorahosted.org/publican"><img alt="Documentation Site" src="Common_Content/images//image_right.png" /></a></p><ul class="docnav top"><li class="previous"><a accesskey="p" href="traceiosect.html"><strong>Prev</strong></a></li><li class="home">SystemTap Beginners Guide</li><li class="next"><a accesskey="n" href="inodewatchsect.html"><strong>Next</strong></a></li></ul><div xml:lang="en-US" class="section" lang="en-US"><div class="titlepage"><div><div><h3 class="title"><a id="traceio2sect"></a>5.2.4. I/O Monitoring (By Device)</h3></div></div></div><a id="idm47951460871504" class="indexterm"></a><a id="idm47951475125568" class="indexterm"></a><a id="idm47951466270576" class="indexterm"></a><a id="idm47951468336480" class="indexterm"></a><a id="idm47951416383104" class="indexterm"></a><div class="para"> This section describes how to monitor I/O activity on a specific device. </div><div class="formalpara"><div xmlns:d="http://docbook.org/ns/docbook" class="title">traceio2.stp</div> <pre class="programlisting">#! /usr/bin/env stap global device_of_interest probe begin { /* The following is not the most efficient way to do this. One could directly put the result of usrdev2kerndev() into device_of_interest. However, want to test out the other device functions */ dev = usrdev2kerndev($1) device_of_interest = MKDEV(MAJOR(dev), MINOR(dev)) } probe vfs.write, vfs.read { if (dev == device_of_interest) printf ("%s(%d) %s 0x%x\n", execname(), pid(), probefunc(), dev) } </pre> </div><a id="idm47951471276752" class="indexterm"></a><a id="idm47951427975520" class="indexterm"></a><a id="idm47951424717712" class="indexterm"></a><a id="idm47951471222928" class="indexterm"></a><a id="idm47951427967808" class="indexterm"></a><a id="idm47951457641664" class="indexterm"></a><div class="para"> <a class="xref" href="traceio2sect.html#traceio2">traceio2.stp</a> takes 1 argument: the whole device number. To get this number, use <code class="command">stat -c "0x%D" <em class="replaceable"><code>directory</code></em></code>, where <code class="command"><em class="replaceable"><code>directory</code></em></code> is located in the device to be monitored. </div><a id="idm47951456527008" class="indexterm"></a><a id="idm47951421614416" class="indexterm"></a><a id="idm47951423497344" class="indexterm"></a><div class="para"> The <code class="command">usrdev2kerndev()</code> function converts the whole device number into the format understood by the kernel. The output produced by <code class="command">usrdev2kerndev()</code> is used in conjunction with the <code class="command">MKDEV()</code>, <code class="command">MINOR()</code>, and <code class="command">MAJOR()</code> functions to determine the major and minor numbers of a specific device. </div><div class="para"> The output of <a class="xref" href="traceio2sect.html#traceio2">traceio2.stp</a> includes the name and ID of any process performing a read/write, the function it is performing (that is, <code class="command">vfs_read</code> or <code class="command">vfs_write</code>), and the kernel device number. </div><div class="para"> The following example is an excerpt from the full output of <code class="command">stap traceio2.stp 0x805</code>, where <code class="literal">0x805</code> is the whole device number of <code class="filename">/home</code>. <code class="filename">/home</code> resides in <code class="filename">/dev/sda5</code>, which is the device we wish to monitor. </div><div class="example"><a id="traceio2output"></a><p class="title"><strong>Example 5.9. <a class="xref" href="traceio2sect.html#traceio2">traceio2.stp</a> Sample Output</strong></p><div class="example-contents"><pre class="screen">[...] synergyc(3722) vfs_read 0x800005 synergyc(3722) vfs_read 0x800005 cupsd(2889) vfs_write 0x800005 cupsd(2889) vfs_write 0x800005 cupsd(2889) vfs_write 0x800005 [...]</pre></div></div><br class="example-break" /></div><ul class="docnav"><li class="previous"><a accesskey="p" href="traceiosect.html"><strong>Prev</strong>5.2.3. Track Cumulative IO</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="inodewatchsect.html"><strong>Next</strong>5.2.5. Monitoring Reads and Writes to a File</a></li></ul></body></html>
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