plugins/org.eclipse.mat.ui.help/gettingstarted/basictutorial.html - mat/org.eclipse.mat - Git at Google

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE html
   PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-us" lang="en-us">
 <head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />

 <meta name="generator" content="DITA-OT" /><meta name="DC.type" content="task" />
 <meta name="DC.title" content="Basic Tutorial" />
 <meta name="DC.relation" scheme="URI" content="../concepts/dominatortree.html" />
 <meta name="DC.relation" scheme="URI" content="../concepts/gcroots.html" />
 <meta name="copyright" content="Copyright (c) 2008, 2023 SAP AG, IBM Corporation and others. All rights reserved. This program and the accompanying materials are made available under the terms of the Eclipse Public License 2.0 which accompanies this distribution, and is available at https://www.eclipse.org/legal/epl-2.0/ " type="primary" />
 <meta name="DC.rights.owner" content="Copyright (c) 2008, 2023 SAP AG, IBM Corporation and others. All rights reserved. This program and the accompanying materials are made available under the terms of the Eclipse Public License 2.0 which accompanies this distribution, and is available at https://www.eclipse.org/legal/epl-2.0/ " type="primary" />
 <meta name="DC.format" content="XHTML" />
 <meta name="DC.identifier" content="task_basictutorial" />
 <meta name="DC.language" content="en-us" />
 <link rel="stylesheet" type="text/css" href="../styles/commonltr.css" />
 <title>Basic Tutorial</title>
 </head>
 <body id="task_basictutorial">

 	<h1 class="title topictitle1" id="ariaid-title1">Basic Tutorial</h1>


 	<div class="body taskbody">
 		<div class="section prereq p">
 			<p class="p">
 				If you are using Memory Analyzer installed into Eclipse rather than
 				a stand-alone Memory Analyzer,
 				first open the 'Memory Analysis'
 				perspective using:
 				<span class="ph menucascade"><span class="ph uicontrol">Window</span><abbr title="and then"> &gt; </abbr><span class="ph uicontrol">Perspective</span><abbr title="and then"> &gt; </abbr><span class="ph uicontrol">Open Perspective</span><abbr title="and then"> &gt; </abbr><span class="ph uicontrol">Other ...</span><abbr title="and then"> &gt; </abbr><span class="ph uicontrol">Memory Analysis</span></span>
 			</p>

 		</div>

 		<div class="section context">
 			<p class="p">
 				This tutorial provides a "jumping-off place" to get familiar with
 				Memory Analyzer.
 			</p>

 		</div>

 		<ol class="ol steps"><li class="li step stepexpand">
 				<span class="ph cmd">
 					<strong class="ph b">Get a Heap Dump</strong>
 				</span>
 				<div class="itemgroup info">
 					<p class="p">
 						The Memory Analyzer works with
 						<a class="xref" href="../concepts/heapdump.html">heap dumps</a>
 						. Such a heap dump contains information about all Java objects
 						alive
 						at a given point in time. All current Java Virtual Machines
 						can
 						write heap dumps, but the exact steps depend on vendor, version
 						and
 						operation system. Find out more in the section
 						<a class="xref" href="../tasks/acquiringheapdump.html">Acquiring Heap Dumps</a>
 						.
 					</p>

 				</div>
 				<ol type="a" class="ol substeps">
 					<li class="li substep substepexpand">
 						<span class="ph cmd">
 							Open
 							<img class="image" src="../mimes/me76fc4.png" alt="" />
 							<a class="xref" href="javascript:liveAction(%22org.eclipse.mat.ui%22,%22org.eclipse.mat.ui.snapshot.actions.OpenSampleHeapDumpAction%22,%22org.eclipse.mat.ui.help/heapdump/HeapDumpSample.hprof%22)">
 								a sample heap dump
 							</a>
 							if you view this page inside the Eclipse help center.
 						</span>
 					</li>

 					<li class="li substep substepexpand">
 						<span class="ph cmd">Start your application with Java 6</span>
 						<div class="itemgroup info">
 							<p class="p">
 								For the purpose of this tutorial, we use Java 6 and JConsole
 								on
 								Windows.
 							</p>

 						</div>
 					</li>

 					<li class="li substep substepexpand">
 						<span class="ph cmd">
 							Start
 							<code class="ph codeph">&lt;jre6&gt;/bin/jconsole.exe</code>
 							and select the running application (in this case Eclipse):
 						</span>
 						<div class="itemgroup stepresult">
 							<img class="image" src="basictutorial_jconsole_open.png" alt="JConsole dialog to open a connection to a Virtual Machine." />
 						</div>
 					</li>

 					<li class="li substep substepexpand">
 						<span class="ph cmd">
 							Select the operation
 							<em class="ph i">dumpHeap</em>
 							from the
 							<em class="ph i">com.sun.management.HotSpotDiagnostic</em>
 							MBean.
 						</span>
 						<div class="itemgroup info">
 							The first parameter
 							<em class="ph i">p0</em>
 							is the full path to the heap dump file. Make sure you give it the
 							file extension .hprof. The second parameter
 							<em class="ph i">p1</em>
 							should be left at true as we are only interested in live objects.
 						</div>
 						<div class="itemgroup stepresult">
 							<img class="image" src="basictutorial_jconsole_mbean.png" alt="Select the dumpHeap method of the HotspotDiagnostics mbean." />
 						</div>
 					</li>

 					<li class="li substep substepexpand">
 						<span class="ph cmd">
 							Select the operation
 							<em class="ph i">triggerDumpToFile</em>
 							from the
 							<em class="ph i">openj9.lang.management=OpenJ9Diagnostics</em>
 							MBean.
 						</span>
 						<div class="itemgroup info">
 							<ul class="ul">
 							<li class="li">For OpenJ9/Semeru based JVMs (build openj9-0.18.0 and later), the parameters are:
 							<dl class="dl parml">

 							<dt class="dt pt dlterm">p0</dt>

 							<dd class="dd pd">
 							is the dump type and should be one of <kbd class="ph userinput">java</kbd>, <kbd class="ph userinput">heap</kbd> or <kbd class="ph userinput">system</kbd>.
 							</dd>


 							<dt class="dt pt dlterm">p1</dt>

 							<dd class="dd pd">
 							is the full path to the dump file or directory. Make sure you give it the
 							appropriate file extension <kbd class="ph userinput">.txt</kbd>, <kbd class="ph userinput">.phd</kbd> or <kbd class="ph userinput">.dmp</kbd>.
 							</dd>


 							</dl>

 							See <a class="xref" href="https://eclipse.dev/openj9/docs/api/jdk17/jdk.management/openj9/lang/management/OpenJ9DiagnosticsMXBean.html" target="_blank">API documentation for <code class="ph codeph">Interface OpenJ9DiagnosticsMXBean</code></a>
 							</li>

 							</ul>

 						</div>
 						<div class="itemgroup stepresult">
 							Note the name of the file.
 						</div>
 					</li>

 					<li class="li substep substepexpand">
 						<span class="ph cmd">Acquire a heap dump directly using Eclipse Memory Analyzer
 						</span>
 						<div class="itemgroup info">
 							<p class="p">
 								See
 								<a class="xref" href="../tasks/acquiringheapdump.html#task_acquiringheapdump__acquire">
 									Acquire Heap Dump from Memory Analyzer
 								</a>
 								to acquire a heap dump from a locally running Java process
 								directly using Eclipse Memory Analyzer.
 								The actual Eclipse Memory
 								Analyzer process could be used as a
 								example Java process to
 								generate a example heap dump.
 							</p>

 						</div>
 					</li>

 				</ol>

 			</li>
 <li class="li step stepexpand" id="task_basictutorial__overview">
 				<span class="ph cmd">
 					<strong class="ph b">Examine the Overview</strong>
 				</span>
 				<div class="itemgroup info">
 					Open the heap dump via
 					<span class="ph menucascade"><span class="ph uicontrol">File</span><abbr title="and then"> &gt; </abbr><span class="ph uicontrol">
 							<img class="image" src="../mimes/i-openhd.png" alt="" />
 							Open Heap Dump...
 						</span></span>
 					to see the overview page.
 					If you have a heap dump available, try <a class="xref" href="javascript:executeCommand(%22org.eclipse.mat.ui.actions.openHeapDump%22)">
 					<strong class="ph b">Open Heap Dump</strong></a> now.
 				</div>
 				<div class="itemgroup stepresult">
 					<img class="image" src="basictutorial_overview.png" alt="Memory Analyzer's overview page for a heap dump" />

 					<p class="p">
 						On the right, you'll find the size of the dump and the number of
 						classes, objects and class loaders.
 					</p>

 					<p class="p">
 						If the total size of the dump is much smaller than the size of the
 						file it is possible
 						that the heap dump contained many 'garbage'
 						objects which would be
 						discarded at the next garbage
 						collection. See
 						the
 						<a class="xref" href="../reference/inspections/unreachable_objects.html" title="Find out more about objects that could or should be garbage collected.">unreachable objects</a>
 						query to examine these 'garbage' objects.
 					</p>

 					<p class="p">
 						Right below, the pie chart gives an impression on the biggest
 						objects in the dump. Move your mouse over a slice to see the
 						details
 						of the objects in the object inspector on the left. Click
 						on any
 						slice to drill down and follow for example the outgoing
 						references.
 					</p>

 				</div>
 			</li>
 <li class="li step stepexpand" id="task_basictutorial__histogram">
 				<span class="ph cmd">
 					<strong class="ph b">Get the Histogram</strong>
 				</span>
 				<div class="itemgroup info">
 					Select the
 					<a class="xref" href="javascript:executeCommand(%22org.eclipse.mat.ui.actions.executeInspection(org.eclipse.mat.ui.actions.executeInspection.commandName=histogram)%22)">
 						<span class="ph uicontrol">
 							<img class="image" src="../mimes/i-histogram.png" alt="histogram icon" />
 							histogram
 						</span>
 					icon
 					</a>
 					from the tool bar to list the number of instances per class,
 					the
 					<a class="xref" href="../concepts/shallowretainedheap.html">shallow size</a>
 					and the
 					<a class="xref" href="../concepts/shallowretainedheap.html">retained size</a>
 					.
 				</div>
 				<div class="itemgroup stepresult">
 					<img class="image" src="basictutorial_histogram.png" alt="Histogram" />

 					<p class="p">
 						The Memory Analyzer displays by default the retained size of
 						individual objects. However, the retained size of a set of objects
 						-
 						in this case all instances of a particular class - needs to be
 						calculated.
 					</p>


 					<p class="p">
 						To approximate the retained sizes for all rows, pick
 						<img class="image" src="../mimes/i-calcrs.png" alt="Calculate retained size" />
 						icon
 						from the tool bar. Alternatively, select a couple rows and use
 						the
 						context menu.
 					</p>


 					<img class="image" src="basictutorial_calc_retained.png" alt="Select calculate retained sizes from the tool bar" />

 					<p class="p">
 						Using the
 						<strong class="ph b">context menu</strong>
 						, you can drill-down into the set of objects
 						which the selected row
 						represents. For example, you can list the
 						objects with outgoing or
 						incoming references. Or group the objects
 						by the value of an
 						attribute. Or group the collections by their
 						size. Or or or...
 					</p>


 					<p class="p">
 						One thing that makes the Memory Analyzer so powerful is the fact
 						that one can run any action on any set of objects. Just drill down
 						and slice your objects the way you need them.
 					</p>


 					<img class="image" src="basictutorial_context_menu.png" alt="Drill down via the context menu" />

 					<p class="p">
 						Another important feature is the facility to
 						<strong class="ph b">group any histogram by class loader, packages or superclass</strong>
 						.
 					</p>


 					<img class="image" src="basictutorial_group_by.png" alt="Group the histogram by class loader or package via the tool bar" />

 					<p class="p">
 						Any decent application loads different components by different
 						class loaders. The Memory Analyzer attaches a meaningful label to
 						the class loader - in the case of OSGi bundles it is the bundle
 						id.
 						Therefore it becomes a lot easier to divide the heap dump into
 						smaller parts.
 					</p>


 					<p class="p">
 						More:
 						<a class="xref" href="../tasks/analyzingclassloader.html" title="Class loaders load classes into the memory of the JVM. When analyzing the heap, class loaders are very important for two reasons: First, applications typically load components using separate class loaders. Second, the loaded classes are usually stored in a separate space (e.g. the perm space) which can also be depleted.">Analyze Class Loader</a>
 					</p>


 					<img class="image" src="basictutorail_by_classloader.png" alt="Histogram grouped by class loader" />

 					<p class="p">
 						Grouping the histogram by packages allows to drill-down along
 						the
 						Java package hierarchy.
 					</p>


 					<img class="image" src="basictutorail_by_package.png" alt="Histogram grouped by packages" />

 					<p class="p">
 						Grouping the histogram by superclass provides an easy way to
 						find for
 						example all the subclasses of java.util.AbstractMap,
 						etc...
 					</p>


 					<img class="image" src="basictutorial_by_superclass.png" alt="Histogram grouped by superclass" />
 				</div>
 			</li>
 <li class="li step stepexpand">
 				<span class="ph cmd">
 					<strong class="ph b">View the Dominator Tree</strong>
 				</span>
 				<div class="itemgroup info">
 					<p class="p">
 						Select the
 						<a class="xref" href="javascript:executeCommand(%22org.eclipse.mat.ui.actions.executeInspection(org.eclipse.mat.ui.actions.executeInspection.commandName=dominator_tree)%22)">
 							<span class="ph uicontrol">
 							<img class="image" src="../mimes/i-dominatortree.png" alt="dominator tree icon" />
 							dominator tree
 							</span>
 							icon
 						</a>
 						from the tool bar to display the dominator tree.
 						The
 						<a class="xref" href="../concepts/dominatortree.html">dominator tree</a>
 						displays the biggest objects in the heap dump. The next level of
 						the
 						tree lists those objects that would be garbage collected if all
 						incoming references to the parent node were removed.
 					</p>


 					<p class="p">
 						The dominator tree is a powerful tool to investigate which
 						objects
 						keep which other objects alive. Again, the tree can be
 						grouped by
 						class loader (e.g. components) and packages to ease the
 						analysis.
 					</p>

 				</div>
 				<div class="itemgroup stepresult">
 					<img class="image" src="basictutorial_dominator_tree.png" alt="Dominator Tree" />
 				</div>
 			</li>
 <li class="li step stepexpand">
 				<span class="ph cmd">
 					<strong class="ph b">Path to GC Roots</strong>
 				</span>
 				<div class="itemgroup info">
 					<p class="p">
 						<a class="xref" href="../concepts/gcroots.html">Garbage Collections Roots (GC roots)</a>
 						are objects that are kept alive by the Virtual Machines itself.
 						These include for example the thread objects of the threads
 						currently running, objects currently on the call stack and classes
 						loaded by the system class loader.
 					</p>


 					<p class="p">
 						The (reverse) reference chain from an object to a GC root - the
 						so
 						called path to GC roots - explains why the object cannot be
 						garbage
 						collected. The path helps solving the classical memory leak
 						in
 						Java:
 						those leaks exist because an object is still referenced
 						even though
 						the program logic will not access the object anymore.
 					</p>


 					<img class="image" src="basictutorial_path_menu.png" alt="Select path to GC roots from the context menu" />
 				</div>
 				<div class="itemgroup stepresult">

 					<p class="p">
 						Initially, the GC root reached by the shortest path is selected.
 					</p>


 					<img class="image" src="basictutorial_path.png" alt="Path to GC roots" />
 				</div>
 			</li>
 <li class="li step stepexpand">
 				<span class="ph cmd">
 					<strong class="ph b">Generate the Leak Report</strong>
 				</span>
 				<div class="itemgroup info">
 					<p class="p">
 						The Memory Analyzer can inspect the heap dump for leak suspects,
 						e.g. objects or set of objects which are suspiciously big.
 					</p>

 					<img class="image" src="basictutorial_run_leak_suspects.png" alt="Run the leak report" />

 					<p class="p">
 						Learn more in this blog posting:
 						<a class="xref" href="https://memoryanalyzer.blogspot.com/2008/05/automated-heap-dump-analysis-finding.html" target="_blank">Automated Heap Dump Analysis: Finding Memory Leaks with One
 							Click
 						</a>
 						.
 					</p>

 				</div>
 				<div class="itemgroup stepresult">
 					See
 					<a class="xref" href="../tasks/runningleaksuspectreport.html">running leak suspect report</a>
 					for information about the report.
 				</div>
 			</li>
 </ol>

 	</div>

 	<div class="related-links">
 <div class="linklist relinfo relconcepts" xml:lang="en-us" lang="en-us"><strong>Related concepts</strong><br />
 <ul class="linklist">
 <li class="linklist"><a class="link" href="../concepts/dominatortree.html">Dominator Tree</a></li>
 <li class="linklist"><a class="link" href="../concepts/gcroots.html">Garbage Collection Roots</a></li></ul></div>
 </div>
 </body>
 </html>
	<?xml version="1.0" encoding="UTF-8"?>
	<!DOCTYPE html
	PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
	<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-us" lang="en-us">
	<head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />

	<meta name="generator" content="DITA-OT" /><meta name="DC.type" content="task" />
	<meta name="DC.title" content="Basic Tutorial" />
	<meta name="DC.relation" scheme="URI" content="../concepts/dominatortree.html" />
	<meta name="DC.relation" scheme="URI" content="../concepts/gcroots.html" />
	<meta name="copyright" content="Copyright (c) 2008, 2023 SAP AG, IBM Corporation and others. All rights reserved. This program and the accompanying materials are made available under the terms of the Eclipse Public License 2.0 which accompanies this distribution, and is available at https://www.eclipse.org/legal/epl-2.0/ " type="primary" />
	<meta name="DC.rights.owner" content="Copyright (c) 2008, 2023 SAP AG, IBM Corporation and others. All rights reserved. This program and the accompanying materials are made available under the terms of the Eclipse Public License 2.0 which accompanies this distribution, and is available at https://www.eclipse.org/legal/epl-2.0/ " type="primary" />
	<meta name="DC.format" content="XHTML" />
	<meta name="DC.identifier" content="task_basictutorial" />
	<meta name="DC.language" content="en-us" />
	<link rel="stylesheet" type="text/css" href="../styles/commonltr.css" />
	<title>Basic Tutorial</title>
	</head>
	<body id="task_basictutorial">

	<h1 class="title topictitle1" id="ariaid-title1">Basic Tutorial</h1>



	<div class="body taskbody">
	<div class="section prereq p">
	<p class="p">
	If you are using Memory Analyzer installed into Eclipse rather than
	a stand-alone Memory Analyzer,
	first open the 'Memory Analysis'
	perspective using:
	<span class="ph menucascade"><span class="ph uicontrol">Window</span><abbr title="and then"> > </abbr><span class="ph uicontrol">Perspective</span><abbr title="and then"> > </abbr><span class="ph uicontrol">Open Perspective</span><abbr title="and then"> > </abbr><span class="ph uicontrol">Other ...</span><abbr title="and then"> > </abbr><span class="ph uicontrol">Memory Analysis</span></span>
	</p>

	</div>

	<div class="section context">
	<p class="p">
	This tutorial provides a "jumping-off place" to get familiar with
	Memory Analyzer.
	</p>

	</div>

	<ol class="ol steps"><li class="li step stepexpand">
	<span class="ph cmd">
	<strong class="ph b">Get a Heap Dump</strong>
	</span>
	<div class="itemgroup info">
	<p class="p">
	The Memory Analyzer works with
	<a class="xref" href="../concepts/heapdump.html">heap dumps</a>
	. Such a heap dump contains information about all Java objects
	alive
	at a given point in time. All current Java Virtual Machines
	can
	write heap dumps, but the exact steps depend on vendor, version
	and
	operation system. Find out more in the section
	<a class="xref" href="../tasks/acquiringheapdump.html">Acquiring Heap Dumps</a>
	.
	</p>

	</div>
	<ol type="a" class="ol substeps">
	<li class="li substep substepexpand">
	<span class="ph cmd">
	Open
	<img class="image" src="../mimes/me76fc4.png" alt="" />
	<a class="xref" href="javascript:liveAction(%22org.eclipse.mat.ui%22,%22org.eclipse.mat.ui.snapshot.actions.OpenSampleHeapDumpAction%22,%22org.eclipse.mat.ui.help/heapdump/HeapDumpSample.hprof%22)">
	a sample heap dump
	</a>
	if you view this page inside the Eclipse help center.
	</span>
	</li>

	<li class="li substep substepexpand">
	<span class="ph cmd">Start your application with Java 6</span>
	<div class="itemgroup info">
	<p class="p">
	For the purpose of this tutorial, we use Java 6 and JConsole
	on
	Windows.
	</p>

	</div>
	</li>

	<li class="li substep substepexpand">
	<span class="ph cmd">
	Start
	<code class="ph codeph"><jre6>/bin/jconsole.exe</code>
	and select the running application (in this case Eclipse):
	</span>
	<div class="itemgroup stepresult">
	<img class="image" src="basictutorial_jconsole_open.png" alt="JConsole dialog to open a connection to a Virtual Machine." />
	</div>
	</li>

	<li class="li substep substepexpand">
	<span class="ph cmd">
	Select the operation
	<em class="ph i">dumpHeap</em>
	from the
	<em class="ph i">com.sun.management.HotSpotDiagnostic</em>
	MBean.
	</span>
	<div class="itemgroup info">
	The first parameter
	<em class="ph i">p0</em>
	is the full path to the heap dump file. Make sure you give it the
	file extension .hprof. The second parameter
	<em class="ph i">p1</em>
	should be left at true as we are only interested in live objects.
	</div>
	<div class="itemgroup stepresult">
	<img class="image" src="basictutorial_jconsole_mbean.png" alt="Select the dumpHeap method of the HotspotDiagnostics mbean." />
	</div>
	</li>

	<li class="li substep substepexpand">
	<span class="ph cmd">
	Select the operation
	<em class="ph i">triggerDumpToFile</em>
	from the
	<em class="ph i">openj9.lang.management=OpenJ9Diagnostics</em>
	MBean.
	</span>
	<div class="itemgroup info">
	<ul class="ul">
	<li class="li">For OpenJ9/Semeru based JVMs (build openj9-0.18.0 and later), the parameters are:
	<dl class="dl parml">

	<dt class="dt pt dlterm">p0</dt>

	<dd class="dd pd">
	is the dump type and should be one of <kbd class="ph userinput">java</kbd>, <kbd class="ph userinput">heap</kbd> or <kbd class="ph userinput">system</kbd>.
	</dd>



	<dt class="dt pt dlterm">p1</dt>

	<dd class="dd pd">
	is the full path to the dump file or directory. Make sure you give it the
	appropriate file extension <kbd class="ph userinput">.txt</kbd>, <kbd class="ph userinput">.phd</kbd> or <kbd class="ph userinput">.dmp</kbd>.
	</dd>


	</dl>

	See <a class="xref" href="https://eclipse.dev/openj9/docs/api/jdk17/jdk.management/openj9/lang/management/OpenJ9DiagnosticsMXBean.html" target="_blank">API documentation for <code class="ph codeph">Interface OpenJ9DiagnosticsMXBean</code></a>
	</li>

	</ul>

	</div>
	<div class="itemgroup stepresult">
	Note the name of the file.
	</div>
	</li>

	<li class="li substep substepexpand">
	<span class="ph cmd">Acquire a heap dump directly using Eclipse Memory Analyzer
	</span>
	<div class="itemgroup info">
	<p class="p">
	See
	<a class="xref" href="../tasks/acquiringheapdump.html#task_acquiringheapdump__acquire">
	Acquire Heap Dump from Memory Analyzer
	</a>
	to acquire a heap dump from a locally running Java process
	directly using Eclipse Memory Analyzer.
	The actual Eclipse Memory
	Analyzer process could be used as a
	example Java process to
	generate a example heap dump.
	</p>

	</div>
	</li>

	</ol>

	</li>
	<li class="li step stepexpand" id="task_basictutorial__overview">
	<span class="ph cmd">
	<strong class="ph b">Examine the Overview</strong>
	</span>
	<div class="itemgroup info">
	Open the heap dump via
	<span class="ph menucascade"><span class="ph uicontrol">File</span><abbr title="and then"> > </abbr><span class="ph uicontrol">
	<img class="image" src="../mimes/i-openhd.png" alt="" />
	Open Heap Dump...
	</span></span>
	to see the overview page.
	If you have a heap dump available, try <a class="xref" href="javascript:executeCommand(%22org.eclipse.mat.ui.actions.openHeapDump%22)">
	<strong class="ph b">Open Heap Dump</strong></a> now.
	</div>
	<div class="itemgroup stepresult">
	<img class="image" src="basictutorial_overview.png" alt="Memory Analyzer's overview page for a heap dump" />

	<p class="p">
	On the right, you'll find the size of the dump and the number of
	classes, objects and class loaders.
	</p>

	<p class="p">
	If the total size of the dump is much smaller than the size of the
	file it is possible
	that the heap dump contained many 'garbage'
	objects which would be
	discarded at the next garbage
	collection. See
	the
	<a class="xref" href="../reference/inspections/unreachable_objects.html" title="Find out more about objects that could or should be garbage collected.">unreachable objects</a>
	query to examine these 'garbage' objects.
	</p>

	<p class="p">
	Right below, the pie chart gives an impression on the biggest
	objects in the dump. Move your mouse over a slice to see the
	details
	of the objects in the object inspector on the left. Click
	on any
	slice to drill down and follow for example the outgoing
	references.
	</p>

	</div>
	</li>
	<li class="li step stepexpand" id="task_basictutorial__histogram">
	<span class="ph cmd">
	<strong class="ph b">Get the Histogram</strong>
	</span>
	<div class="itemgroup info">
	Select the
	<a class="xref" href="javascript:executeCommand(%22org.eclipse.mat.ui.actions.executeInspection(org.eclipse.mat.ui.actions.executeInspection.commandName=histogram)%22)">
	<span class="ph uicontrol">
	<img class="image" src="../mimes/i-histogram.png" alt="histogram icon" />
	histogram
	</span>
	icon
	</a>
	from the tool bar to list the number of instances per class,
	the
	<a class="xref" href="../concepts/shallowretainedheap.html">shallow size</a>
	and the
	<a class="xref" href="../concepts/shallowretainedheap.html">retained size</a>
	.
	</div>
	<div class="itemgroup stepresult">
	<img class="image" src="basictutorial_histogram.png" alt="Histogram" />

	<p class="p">
	The Memory Analyzer displays by default the retained size of
	individual objects. However, the retained size of a set of objects
	-
	in this case all instances of a particular class - needs to be
	calculated.
	</p>


	<p class="p">
	To approximate the retained sizes for all rows, pick
	<img class="image" src="../mimes/i-calcrs.png" alt="Calculate retained size" />
	icon
	from the tool bar. Alternatively, select a couple rows and use
	the
	context menu.
	</p>


	<img class="image" src="basictutorial_calc_retained.png" alt="Select calculate retained sizes from the tool bar" />

	<p class="p">
	Using the
	<strong class="ph b">context menu</strong>
	, you can drill-down into the set of objects
	which the selected row
	represents. For example, you can list the
	objects with outgoing or
	incoming references. Or group the objects
	by the value of an
	attribute. Or group the collections by their
	size. Or or or...
	</p>


	<p class="p">
	One thing that makes the Memory Analyzer so powerful is the fact
	that one can run any action on any set of objects. Just drill down
	and slice your objects the way you need them.
	</p>


	<img class="image" src="basictutorial_context_menu.png" alt="Drill down via the context menu" />

	<p class="p">
	Another important feature is the facility to
	<strong class="ph b">group any histogram by class loader, packages or superclass</strong>
	.
	</p>


	<img class="image" src="basictutorial_group_by.png" alt="Group the histogram by class loader or package via the tool bar" />

	<p class="p">
	Any decent application loads different components by different
	class loaders. The Memory Analyzer attaches a meaningful label to
	the class loader - in the case of OSGi bundles it is the bundle
	id.
	Therefore it becomes a lot easier to divide the heap dump into
	smaller parts.
	</p>


	<p class="p">
	More:
	<a class="xref" href="../tasks/analyzingclassloader.html" title="Class loaders load classes into the memory of the JVM. When analyzing the heap, class loaders are very important for two reasons: First, applications typically load components using separate class loaders. Second, the loaded classes are usually stored in a separate space (e.g. the perm space) which can also be depleted.">Analyze Class Loader</a>
	</p>


	<img class="image" src="basictutorail_by_classloader.png" alt="Histogram grouped by class loader" />

	<p class="p">
	Grouping the histogram by packages allows to drill-down along
	the
	Java package hierarchy.
	</p>


	<img class="image" src="basictutorail_by_package.png" alt="Histogram grouped by packages" />

	<p class="p">
	Grouping the histogram by superclass provides an easy way to
	find for
	example all the subclasses of java.util.AbstractMap,
	etc...
	</p>


	<img class="image" src="basictutorial_by_superclass.png" alt="Histogram grouped by superclass" />
	</div>
	</li>
	<li class="li step stepexpand">
	<span class="ph cmd">
	<strong class="ph b">View the Dominator Tree</strong>
	</span>
	<div class="itemgroup info">
	<p class="p">
	Select the
	<a class="xref" href="javascript:executeCommand(%22org.eclipse.mat.ui.actions.executeInspection(org.eclipse.mat.ui.actions.executeInspection.commandName=dominator_tree)%22)">
	<span class="ph uicontrol">
	<img class="image" src="../mimes/i-dominatortree.png" alt="dominator tree icon" />
	dominator tree
	</span>
	icon
	</a>
	from the tool bar to display the dominator tree.
	The
	<a class="xref" href="../concepts/dominatortree.html">dominator tree</a>
	displays the biggest objects in the heap dump. The next level of
	the
	tree lists those objects that would be garbage collected if all
	incoming references to the parent node were removed.
	</p>


	<p class="p">
	The dominator tree is a powerful tool to investigate which
	objects
	keep which other objects alive. Again, the tree can be
	grouped by
	class loader (e.g. components) and packages to ease the
	analysis.
	</p>

	</div>
	<div class="itemgroup stepresult">
	<img class="image" src="basictutorial_dominator_tree.png" alt="Dominator Tree" />
	</div>
	</li>
	<li class="li step stepexpand">
	<span class="ph cmd">
	<strong class="ph b">Path to GC Roots</strong>
	</span>
	<div class="itemgroup info">
	<p class="p">
	<a class="xref" href="../concepts/gcroots.html">Garbage Collections Roots (GC roots)</a>
	are objects that are kept alive by the Virtual Machines itself.
	These include for example the thread objects of the threads
	currently running, objects currently on the call stack and classes
	loaded by the system class loader.
	</p>


	<p class="p">
	The (reverse) reference chain from an object to a GC root - the
	so
	called path to GC roots - explains why the object cannot be
	garbage
	collected. The path helps solving the classical memory leak
	in
	Java:
	those leaks exist because an object is still referenced
	even though
	the program logic will not access the object anymore.
	</p>


	<img class="image" src="basictutorial_path_menu.png" alt="Select path to GC roots from the context menu" />
	</div>
	<div class="itemgroup stepresult">

	<p class="p">
	Initially, the GC root reached by the shortest path is selected.
	</p>


	<img class="image" src="basictutorial_path.png" alt="Path to GC roots" />
	</div>
	</li>
	<li class="li step stepexpand">
	<span class="ph cmd">
	<strong class="ph b">Generate the Leak Report</strong>
	</span>
	<div class="itemgroup info">
	<p class="p">
	The Memory Analyzer can inspect the heap dump for leak suspects,
	e.g. objects or set of objects which are suspiciously big.
	</p>

	<img class="image" src="basictutorial_run_leak_suspects.png" alt="Run the leak report" />

	<p class="p">
	Learn more in this blog posting:
	<a class="xref" href="https://memoryanalyzer.blogspot.com/2008/05/automated-heap-dump-analysis-finding.html" target="_blank">Automated Heap Dump Analysis: Finding Memory Leaks with One
	Click
	</a>
	.
	</p>

	</div>
	<div class="itemgroup stepresult">
	See
	<a class="xref" href="../tasks/runningleaksuspectreport.html">running leak suspect report</a>
	for information about the report.
	</div>
	</li>
	</ol>

	</div>

	<div class="related-links">
	<div class="linklist relinfo relconcepts" xml:lang="en-us" lang="en-us"><strong>Related concepts</strong><br />
	<ul class="linklist">
	<li class="linklist"><a class="link" href="../concepts/dominatortree.html">Dominator Tree</a></li>
	<li class="linklist"><a class="link" href="../concepts/gcroots.html">Garbage Collection Roots</a></li></ul></div>
	</div>
	</body>
	</html>