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 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 | <?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. Disk</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="not publican" /><meta xmlns:d="http://docbook.org/ns/docbook" name="package" content="" /><link rel="home" href="index.html" title="SystemTap Beginners Guide" /><link rel="up" href="useful-systemtap-scripts.html" title="Chapter 5. Useful SystemTap Scripts" /><link rel="prev" href="useful-systemtap-scripts.html" title="Chapter 5. Useful SystemTap Scripts" /><link rel="next" href="iotimesect.html" title="5.2.2. Tracking I/O Time For Each File Read or Write" /></head><body><p id="title"></p><ul class="docnav top"><li class="previous"><a accesskey="p" href="useful-systemtap-scripts.html"><strong>Prev</strong></a></li><li class="home">SystemTap Beginners Guide</li><li class="next"><a accesskey="n" href="iotimesect.html"><strong>Next</strong></a></li></ul><div class="section"><div class="titlepage"><div><div><h2 class="title"><a id="mainsect-disk"> </a>5.2. Disk</h2></div></div></div><div class="para">The following sections showcase scripts that monitor disk and I/O activity.</div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="disktop"> </a>5.2.1. Summarizing Disk Read/Write Traffic</h3></div></div></div><a id="idm140174743033280" class="indexterm"></a><a id="idm140174735018528" class="indexterm"></a><a id="idm140174731928464" class="indexterm"></a><a id="idm140174732298512" class="indexterm"></a><a id="idm140174732172000" class="indexterm"></a><a id="idm140174743478544" class="indexterm"></a><a id="idm140174742047120" class="indexterm"></a><a id="idm140174740560848" class="indexterm"></a><div class="para">This section describes how to identify which processes are performing the heaviest disk reads/writes to the system.</div><div class="para"><div xmlns:d="http://docbook.org/ns/docbook" class="title">disktop.stp</div> <pre class="programlisting">#!/usr/bin/env stap # # Copyright (C) 2007 Oracle Corp. # # Get the status of reading/writing disk every 5 seconds, # output top ten entries # # This is free software,GNU General Public License (GPL); # either version 2, or (at your option) any later version. # # Usage: # ./disktop.stp # global io_stat,device global read_bytes,write_bytes probe vfs.read.return { if ($return>0) { if (devname!="N/A") {/*skip read from cache*/ io_stat[pid(),execname(),uid(),ppid(),"R"] += $return device[pid(),execname(),uid(),ppid(),"R"] = devname read_bytes += $return } } } probe vfs.write.return { if ($return>0) { if (devname!="N/A") { /*skip update cache*/ io_stat[pid(),execname(),uid(),ppid(),"W"] += $return device[pid(),execname(),uid(),ppid(),"W"] = devname write_bytes += $return } } } probe timer.ms(5000) { /* skip non-read/write disk */ if (read_bytes+write_bytes) { printf("\n%-25s, %-8s%4dKb/sec, %-7s%6dKb, %-7s%6dKb\n\n", ctime(gettimeofday_s()), "Average:", ((read_bytes+write_bytes)/1024)/5, "Read:",read_bytes/1024, "Write:",write_bytes/1024) /* print header */ printf("%8s %8s %8s %25s %8s %4s %12s\n", "UID","PID","PPID","CMD","DEVICE","T","BYTES") } /* print top ten I/O */ foreach ([process,cmd,userid,parent,action] in io_stat- limit 10) printf("%8d %8d %8d %25s %8s %4s %12d\n", userid,process,parent,cmd, device[process,cmd,userid,parent,action], action,io_stat[process,cmd,userid,parent,action]) /* clear data */ delete io_stat delete device read_bytes = 0 write_bytes = 0 } probe end{ delete io_stat delete device delete read_bytes delete write_bytes } </pre> </div><div class="para"><a class="xref" href="mainsect-disk.html#scriptdisktop">disktop.stp</a> outputs the top ten processes responsible for the heaviest reads/writes to disk. <a class="xref" href="mainsect-disk.html#disktopoutput">Example 5.6, “disktop.stp Sample Output”</a> displays a sample output for this script, and includes the following data per listed process:</div><div xmlns:d="http://docbook.org/ns/docbook" class="itemizedlist"><ul><li class="listitem"><div class="para"><code class="computeroutput">UID</code> — user ID. A user ID of <code class="computeroutput">0</code> refers to the root user.</div></li><li class="listitem"><div class="para"><code class="computeroutput">PID</code> — the ID of the listed process.</div></li><li class="listitem"><div class="para"><code class="computeroutput">PPID</code> — the process ID of the listed process's <span class="emphasis"><em>parent process</em></span>.</div></li><li class="listitem"><div class="para"><code class="computeroutput">CMD</code> — the name of the listed process.</div></li><li class="listitem"><div class="para"><code class="computeroutput">DEVICE</code> — which storage device the listed process is reading from or writing to.</div></li><li class="listitem"><div class="para"><code class="computeroutput">T</code> — the type of action performed by the listed process; <code class="computeroutput">W</code> refers to write, while <code class="computeroutput">R</code> refers to read.</div></li><li class="listitem"><div class="para"><code class="computeroutput">BYTES</code> — the amount of data read to or written from disk.</div></li></ul></div><a id="idm140174732302992" class="indexterm"></a><a id="idm140174733566608" class="indexterm"></a><a id="idm140174735961104" class="indexterm"></a><div class="para">The time and date in the output of <a class="xref" href="mainsect-disk.html#scriptdisktop">disktop.stp</a> is returned by the functions <code class="command">ctime()</code> and <code class="command">gettimeofday_s()</code>. <code class="command">ctime()</code> derives calendar time in terms of seconds passed since the Unix epoch (January 1, 1970). <code class="command">gettimeofday_s()</code> counts the <span class="emphasis"><em>actual</em></span> number of seconds since Unix epoch, which gives a fairly accurate human-readable timestamp for the output.</div><a id="idm140174736349152" class="indexterm"></a><a id="idm140174732592192" class="indexterm"></a><a id="idm140174736673552" class="indexterm"></a><div class="para"> In this script, the <code class="command">$return</code> is a local variable that stores the actual number of bytes each process reads or writes from the virtual file system. <code class="command">$return</code> can only be used in return probes (for example, <code class="command">vfs.read.return</code> and <code class="command">vfs.read.return</code>). </div><div class="example"><a id="disktopoutput"> </a><p class="title"><strong>Example 5.6. <a class="xref" href="mainsect-disk.html#scriptdisktop">disktop.stp</a> Sample Output</strong></p><div class="example-contents"><pre class="screen">[...] Mon Sep 29 03:38:28 2008 , Average: 19Kb/sec, Read: 7Kb, Write: 89Kb UID PID PPID CMD DEVICE T BYTES 0 26319 26294 firefox sda5 W 90229 0 2758 2757 pam_timestamp_c sda5 R 8064 0 2885 1 cupsd sda5 W 1678 Mon Sep 29 03:38:38 2008 , Average: 1Kb/sec, Read: 7Kb, Write: 1Kb UID PID PPID CMD DEVICE T BYTES 0 2758 2757 pam_timestamp_c sda5 R 8064 0 2885 1 cupsd sda5 W 1678</pre></div></div></div></div><ul class="docnav"><li class="previous"><a accesskey="p" href="useful-systemtap-scripts.html"><strong>Prev</strong>Chapter 5. Useful SystemTap Scripts</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="iotimesect.html"><strong>Next</strong>5.2.2. Tracking I/O Time For Each File Read or Wr...</a></li></ul></body></html>
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