| <?xml version="1.0" encoding="UTF-8"?> |
| <!-- |
| Copyright (c) 2008, 2018 SAP AG and IBM Corporation |
| All rights reserved. This program and the accompanying materials |
| are made available under the terms of the Eclipse Public License v1.0 |
| which accompanies this distribution, and is available at |
| http://www.eclipse.org/legal/epl-v10.html |
| |
| Contributors: |
| SAP AG - initial API and implementation |
| Andrew Johnson/IBM Corporation - XML validation |
| --> |
| |
| <cheatsheet title="Component Report"> |
| <!-- |
| xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" |
| xsi:schemaLocation="org.eclipse.ui.cheatsheets platform:/resource/org.eclipse.mat.ui.help/schema/cheatSheetContentFileSpec.xsd" |
| xmlns="org.eclipse.ui.cheatsheets"> |
| --> |
| <intro href="/org.eclipse.mat.ui.help/reference/inspections/component_report.html"> |
| <description> |
| A heap dump contains many objects. But which of those belong to your component? |
| And what conclusions can you draw from them? This is where the <b>Component Report</b> can help. |
| <br/><br/> |
| Press the <b>Help</b> button for more detailed information. |
| </description> |
| </intro> |
| <item |
| href="/org.eclipse.mat.ui.help/tasks/acquiringheapdump.html" |
| skip="true" |
| title="Open a Heap Dump"> |
| <description> |
| The analysis is based on heap dumps. Consult the help pages on how to acquire a heap dump of |
| your application. |
| <br/><br/> |
| If you do not already have a heap dump, use the link below to open a <b>sample heap dump</b>. |
| </description> |
| <action class="org.eclipse.mat.ui.snapshot.actions.OpenSampleHeapDumpAction" |
| pluginId="org.eclipse.mat.ui" |
| confirm="false" |
| param1="org.eclipse.mat.ui.help/heapdump/HeapDumpSample.hprof"/> |
| </item> |
| <item |
| title="Run the Component Report" |
| href="/org.eclipse.mat.ui.help/reference/inspections/component_report.html#ref_inspections_component_report__run"> |
| <description> |
| Before starting, one has to decide what constitutes a component. |
| Typically, a component is either a set of classes in a <b>common root package</b> or classes loaded by the same <b>class loader</b>. |
| <br/><br/> |
| To select a set of packages: |
| <br/><br/> |
| Choose <b>Leak Identification -> Component Report</b> from the Query drop-down list in the toolbar.<br/><br/> |
| Provide a <b>class name pattern</b> (for example java.util.*) and hit Finish. |
| </description> |
| <command |
| required="false" |
| serialization="org.eclipse.mat.ui.actions.executeInspection(org.eclipse.mat.ui.actions.executeInspection.commandName=component_report)"/> |
| <onCompletion>The Component Report consists of HTML pages. It is stored in a ZIP file next to the heap dump file.</onCompletion> |
| </item> |
| <item |
| title="Getting an Overview" |
| href="/org.eclipse.mat.ui.help/reference/inspections/component_report.html#ref_inspections_component_report__overview"> |
| <description> |
| » The <b>size</b> of the component relative to the size of the whole heap.<br/> |
| » The <b>Top Consumer</b> section lists the biggest object, classes, class loader and packages.<br/> |
| » The <b>Retained Set</b> is a histogram of all objects kept alive by the component. |
| </description> |
| </item> |
| <item |
| title="Duplicate Strings" |
| href="/org.eclipse.mat.ui.help/reference/inspections/component_report.html#ref_inspections_component_report__strings"> |
| <description> |
| Duplicate Strings are a prime example for memory waste: multiple char arrays with identical content. |
| <br/><br/> |
| The content of the char arrays typically gives away ideas how to reduce the duplicates. |
| </description> |
| </item> |
| <item |
| title="Empty Collections" |
| href="/org.eclipse.mat.ui.help/reference/inspections/component_report.html#ref_inspections_component_report__emptycol"> |
| <description> |
| Empty collections take up space without storing any data. If only a few collections actually hold data, |
| think about <b>lazy initialization</b>, i.e. create the collection only when needed. |
| </description> |
| </item> |
| <item |
| title="Collection Fill Ratios" |
| href="/org.eclipse.mat.ui.help/reference/inspections/component_report.html#ref_inspections_component_report__colfillratio"> |
| <description> |
| Collections are typically created with a default initial capacity. Many collections with low fill ratios |
| indicate that the <b>initial capacity</b> could be <b>reduced</b>. |
| </description> |
| </item> |
| <item |
| title="Soft Reference Statistics" |
| href="/org.eclipse.mat.ui.help/reference/inspections/component_report.html#ref_inspections_component_report__softref"> |
| <description> |
| Softly referenced objects require more GC activity (possibly during a stop-the-world phase) |
| and should be used in small doses only. |
| </description> |
| </item> |
| <item |
| title="Finalizer Statistics" |
| href="/org.eclipse.mat.ui.help/reference/inspections/component_report.html#ref_inspections_component_report__finalizer"> |
| <description> |
| Finalizers come with a lot of drawbacks: For example, they require multiple Garbage Collections to run |
| until the objects are actually freed. Also, the time of the execution is up to the VM which makes |
| Finalizer unpredictable. |
| </description> |
| </item> |
| <item |
| title="Map Collision Ratios" |
| href="/org.eclipse.mat.ui.help/reference/inspections/component_report.html#ref_inspections_component_report__mapcollision"> |
| <description> |
| Maps place the values in different buckets based on the hash code of the keys. High collision ratios |
| can indicate sub-optimal hash codes. This is not a memory problem (a better hash code does not save |
| space) but rather performance problem because of the (usually) linear access inside the buckets. |
| </description> |
| </item> |
| </cheatsheet> |
