JDK Tools For Performance Diagnostics

JDK tools for performance diagnostics Dror Bereznitsky Director of Technologies, AlphaCSP

Introduction Application to slow ? Image courtesy of WTL photos - flickr 2

Introduction Leaking Memory ? Image courtesy of neoliminal- flickr 3

Intoduction Suffering from deadlocks ? Image courtesy of hfb - flickr 4

Introduction The JDK has tools that can help you … Image courtesy of docman - flickr 5

JDK tools for performance diag. • JDK tools for performance diagnostics:  VisualVM  jconsole  BTrace  jstat  jhat  jinfo  jps  jmap  jstack Image courtesy of dodgechallenger1 - flickr 6

VisualVM 7

VisualVM • Java troubleshooting tool • Visual tool integrating several command line JDK tools and much more • For development and production time 8

VisualVM Features • Display local/remote Java applications • Monitor memory and threads • Take and browse heap + thread dumps • Extensible with plugins • Attach API or JMX 9

VisualVM Plugins • MBean browser • Visual GC • Memory sampler • Profiler – CPU, Memory • BTrace plugin • Direct buffers monitor (JDK 7) • Many more … 10

VisualVM Feature Matrix JDK 1.4.2 JDK 5 JDK 6 JDK 6 Local Remote Overview     System properties  Monitor     Threads    Profiler  Thread Dump  Heap Dump  Heam Dump OOME  MBean Browser    JConsole plugins    11

Supported VMs Java VM Remarks Sun JDK Open JDK Apple JDK Oracle JRockit IBM J9 Using JMX only HP-UX JDK SAP JDK Requires the VisualVM Extensions plugin 12

Getting Started • Version 1.0 ships with JDK6 since update 7 • Look for jvisualvm in your JDK bin directory • Version 1.1.1 now ships with JDK6 update 14 • Latest version can be downloaded from https://visualvm.dev.java.net 13

The Demo Application 14

VisualVM Demo VisualVM Demo 15

Working With Remote Applications • Start a jstatd daemon on the remote host • Allow remote monitoring tools to attach to running JVMs • May have security implications • Add the remote host to the ‘Remote’ node in the Applications window 16

Extending VisualVM What is VisualVM, really? Generic desktop application infrastructure for analyzing sources of data. Default data sources • Applications • Hosts • Dumps • Snapshots 17

Extending VisualVM • Why you would want to extend VisualVM: • Tool-Centric You have a monitoring or management tool that you want to make available to VisualVM • BTrace plugin • Application-Centric You have an application with specific monitoring/management needs • Glassfish plugin 18

Extending VisualVM • What Can You Create? • Tabs: Main tabs, Sub tabs • Actions: Menu items, Toolbar buttons • Application Types • Data Sources 19

Getting Started With Extending VisualVM • Install JDK 6 • Read VisualVM API Javadoc & Tutorials • Create VisualVM modules • Netbeans IDE • VisualVM samples collection 20

VisualVM Usage Scenarios • General health monitoring • Diagnose specific problems • Memory leaks • Deadlocks • Excessive use of finalizers • Hot lock contention • Hung process 21

BTrace 22

BTrace • Dynamic tracing tool for the Java platform • Safe – read, no write • Low-overhead • Tracing code is written in Java • Available as a VisualVM plugin or as a command line tool 23

Dynamic Tracing • Works by dynamically instrumenting classes of a running Java program – using ASM 3.0 • ASM is an all purpose Java bytecode manipulation and analysis framework • Inserts tracing actions by hot- swapping the traced program classes 24

BTrace HelloWorld Example import com.sun.btrace.annotations.*; import static com.sun.btrace.BTraceUtils.*; @BTrace public class HelloWorld { @OnMethod( clazz="java.lang.Thread", method="start" ) public static void func() { println("about to start a thread!"); } } 25

BTrace Terminology • Probe Point • "location" or "event" at which a set of tracing statements are executed. • Trace Actions/Actions • Trace statements that are executed whenever a probe "fires". • Action Methods • Trace statements that are executed when a probe fires • defined inside a static method • Such methods are called "action" methods. 26

BTrace HelloWorld Example import com.sun.btrace.annotations.*; import static com.sun.btrace.BTraceUtils.*; @BTrace public class HelloWorld { @OnMethod( clazz="java.lang.Thread", method="start" Probe Point ) public static void func() { println("about to start a thread!"); Action Method } } 27

Some BTrace Annotations • @OnMethod • Specify target class(es), target method(s) and "location(s)" within the method(s) • @OnLowMemory • Trace memory threshold exceed event • @OnTimer • Specify tracing actions that have to run periodically once every N milliseconds 28

BTrace Restrictions • can not create new objects. • can not create new arrays. • can not throw exceptions. • can not catch exceptions. • can not have loops (for, while, do..while) • Almost everything is restricted … 29

com.sun.btrace.BTraceUtils • Contains 270 public static methods which may be called from a BTrace script • Many useful methods: • deadlocks - prints the Java level deadlocks detected (if any) • dumpHeap - dump the snapshot of the Java heap • jstack - Prints the java stack trace of the current thread 30

Getting Started • BTrace is available as a VisualVM plugin • Requires VisualVM 1.0.1+ • Available at the BTrace plugin center - https://btrace.dev.java.net/uc/updates.xml 31

BTrace Demo Demo 32

BTrace Demo Source @BTrace public class SizeOfStatusCache { @OnMethod( clazz = "com.alphacsp.performance.seminar.twitter.Main", method = "pollForNewStatuses", location = @Location(Kind.RETURN)) public static void onNewStatuses(Object obj) { List statusCache = (List) get(field(classOf(obj), "statusCache", true), obj); println(concat("Number of cached statuses: ", str(size(statusCache)))); } } 33

BTrace Usage Scenarios • Fine grained performance analysis • Runtime profiling and monitoring • Collecting statistics • When no graphic user interface available 34

jhat jhat 35

jhat • Java Heap Analysis Tool • Parses a java heap dump and launches a web server • Basic web interface for browsing the heap dump • Useful for analyzing memory leaks 36

jhat Features • View all class instances • View class classloader • View all references to an object • View reference chains from Rootset • Use OQL (Object Query Language) to query heap dumps 37

OQL • SQL-like query language to query Java heap • Based on JavaScript expression language • Built-in objects and functions • OQL help is available from the jhat OQL screen 38

Getting Started C:jdk1.6.0_13bin>jhat -J-mx512m c:heapdump- 1245057502890.hprof Reading from c:heapdump-1245057502890.hprof... Dump file created Mon Jun 15 12:18:22 IDT 2009 Snapshot read, resolving... Resolving 120908 objects... Chasing references, expect 24 dots........................ Eliminating duplicate references........................ Snapshot resolved. Started HTTP server on port 7000 Server is ready. 39

jhat demo jhat Demo 40

jhat Usage Scenarios • When analyzing large heap dumps – can use a remote powerful server • When you do not have a graphic user interface • If you want to perform smart queries on heap content 41

Summary Summary 42

Summary • The JDK contains useful performance diagnostics tools • These tools can be used for detecting, analyzing and solving performance related issues 43

References • Monitoring and Troubleshooting Java applications using JDK tools (PDF) • VisualVM • VisualVM Sample Collection • TS-4247 Getting More Out of the Java VisualVM Tool (PDF) • btrace • ASM • jhat 44

Thank You  45

JDK Tools For Performance Diagnostics

by Baruch Sadogursky on Jun 23, 2009

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JDK Tools For Performance Diagnostics — Presentation Transcript