Debugging the New Java. Topics. Introduction Overview of the new Virtual Machine IBM i extras Cross-platform debug capabilities Interactive debug

Transcription

1 Agenda Key: Session Number: 26MJ Debugging the New Java Tim Rowe Web Integration on i T/L timmr@us.ibm.com 8 Copyright IBM Corporation, All Rights Reserved. This publication may refer to products that are not currently available in your country. IBM makes no commitment to make available any products referred to herein. Topics Introduction Overview of the new Virtual Machine IBM i extras Cross-platform debug capabilities Interactive debug

2 Introduction IBM i is embracing IBM s new VM for Java. This new VM is called the IBM Technology for Java Virtual Machine (IT4J). IT4J will ultimately replace the Classic VM, which runs only in 64-bit mode. IT4J has both 32-bit and 64-bit versions Introduction (con t) Key terms/abbreviations: IT4J: IBM Technology for Java JVM: Java Virtual Machine VM: Virtual Machine GC: Garbage Collection GCMV: Garbage Collection and Memory Visualizer JIT: Just-in-Time compiler ISA: IBM Support Assistant

3 Agenda Key: Session Number: Overview of the new Virtual Machine 8 Copyright IBM Corporation, All Rights Reserved. This publication may refer to products that are not currently available in your country. IBM makes no commitment to make available any products referred to herein. Why would I try the new VM? Better Performance Usually a 20% (or more) improvement found in real applications Smaller Memory Footprint Usually 50% or more reduction in heap size with 32-bit version. Best of IBM Research and Development The JVM that runs on all IBM Systems This is the future of Java running on IBM i Positioning of the new JVM Should provide a great fit for small applications on small systems Small to Medium Business (SMB) market on IBM i ripe for small JVM Classic VM support will go away IT4J is default VM in V6R1 IT4J is the only VM in V7R1+

4 Things you will no longer have ANZJVM Replaced with WRKJVMJOB DMPJVM Replaced with GENJVMDMP Detailed PEX information PEX still available but with slightly less Java information Java leak analysis via PTDV IBM Support Assistant has tools for debugging Java leaks Classic native macros in Advanced Analysis Replaced with jvminfo Java frames in processinfo macro from Advanced Analysis Still have frames of native methods that are running in PASE Java (4300) VLOG s Now have 4700 VLOG s in crash scenarios Things you ll still have Collection Services JobWatcher Green Screen Debug Java Debug Wire Protocol (JDWP) DSPJVMJOB Java stacks in WRKJOB

5 New things you ll be getting!!! All the industry-standard Java debug tools available for the VM on other platforms. PLUS: jvminfo Advanced Analysis macro, and new CL commands (V6R1+) that make it easy to: Display live statistics and information Generate dumps Enable/Disable Verbose GC (live!) Agenda Key: Session Number: IBM i Extras 8 Copyright IBM Corporation, All Rights Reserved. This publication may refer to products that are not currently available in your country. IBM makes no commitment to make available any products referred to herein.

6 IBM i Extras WRKJVMJOB (V6R1+) PRTJVMJOB (V6R1+) GENJVMDMP (V6R1+) Advanced Analysis WRKJVMJOB Allows you to: Display a list of VM s Display JVM arguments (used to create the VM) Display ILE/PASE environment variables Display Java lock information Display garbage collection information Display initial/current Java system properties Display Java threads Invoke PRTJVMJOB or GENJVMDMP

7 Default is *ALL to identify the job. This will give you a list of active VM s on the system (next slide) All jobs running a JVM All jobs on the system running an active JVM

8 Options shown when you work with a single job.. Display live information Display JVM Arguments Ensure the correct JVM arguments are used for the JVM

9 Display Environment Variables Example use: Ensure your app is running in the proper environment Display Java Lock Information Example use: Inspect a hung job for deadlocks!

10 Display Java Lock Information (Displaying object locks) Display Garbage Collection Information Example use: See how much heap (Java and native) your app is using

11 Display Garbage Collection Information Also, see other basic GC info. F7 prints GC cycle tables (next slides) Printed GC Cycle tables GC data sent to a spooled file.

12 Printed GC Cycle tables Example use: Inspect a hung job for deadlocks! Printed GC Cycle tables

13 Printed GC Cycle tables Printed GC Cycle tables

14 Display Java Threads Thread status, total CPU, AUX I/O Display Java Threads Thread group, Run priority

15 Display Java Threads Thread name Display Java Threads For any thread, you can display it s integrated stack! (next slide)

16 Display Thread Stack Same stack available via WRKJOB PRTJVMJOB/GENJVMDMP PRTJVMJOB Allows you to print information available via WRKACTJOB (and GC cycle tables) GENJVMDMP Allows you request a Java, System, or Heap dump

17 Advanced Analysis jvminfo Gives the user all the capabilities of WRKJVMJOB, PRTJVMJOB, and GENJVMDMP, but without the Green Screen interface. Run jvminfo help for usage information Unlike WRKJVMJOB, PRTJVMJOB, and GENJVMDMP, this is available in V5R4 Agenda Key: Session Number: Cross-platform debug capabilities 8 Copyright IBM Corporation, All Rights Reserved. This publication may refer to products that are not currently available in your country. IBM makes no commitment to make available any products referred to herein.

18 Cross-platform debug capabilities Verbose options VM-generated dumps Java dump System Dump Heap Dump Dump agents Trace engine jextract IBM Support Assistant (ISA) Search GC and Memory Visualizer (GCMV) DumpAnalyzer Verbose options -Xcheck:jni (usually -Xcheck:jni:pedantic) Does checking for correctness and safety with use of Java Native Interface (JNI) function calls -verbose Logs when classes are loaded -verbose:dynload Logs when classes are loaded (more information than -verbose ) -verbose:gc Verbose garbage collection information (can also be turned on on the fly with WRKJVMJOB (V6R1+) or Advanced Analysis. -Xshareclasses:verbose Logs information about the use of shared class cache.

19 VM-generated dumps: Java Dump Human-readable information about the attached threads, loaded classes, startup options, and other useful data. Example name: javacore txt Also known as a javacore or thread dump Generated by: GENJVMDMP in V6R1+ (*JAVA) Advanced analysis jvminfo macro kill quit (by default) uncaught java/lang/outofmemoryerror cases (by default) User-defined dump agent Analyzed with: IBM Support Assistant (ISA) Text editor (human eye). Somewhat complex VM-generated dumps: Java Dump Why you d want it: Inspect suspected deadlocks Use ISA tools like ThreadAnalyzer or IBM Thread and Monitor Dump Analuzer for Java Gain a better understanding of loaded classes and classloaders Inspect basic thread information (Java stacks, state, etc) Inspect input arguments to the VM

20 VM-generated dumps: System Dump Binary format raw memory image of the job. It contains everything in the PASE environment Example name: core dmp Also known as a core file or process dump Generated by: GENJVMDMP in V6R1+ (*SYSTEM) Advanced analysis jvminfo macro Crash scenarios (by default) User-defined dump agent Analyzed with: IBM Support Assistant (ISA) jextract dbx (expert users) VM-generated dumps: System Dump Why you d want it: After running jextract, use ISA tools (like DumpAnalyzier) to: Perform crash analysis See environment variables, thread stacks, etc. Much more! (covered later) After running jextract, submit problem to IBM service Perform advanced debug with the dbx debugger (expert users only) (jextract will be covered later)

21 VM-generated dumps: Heap Dump A dump of all the allocations in the Java object heap. Example name: heapdump phd Portable Heap Dump format Generated by: GENJVMDMP in V6R1+ (*HEAP) Advanced analysis jvminfo macro uncaught java/lang/outofmemoryerror cases (by default) User-defined dump agent Analyzed with: IBM Support Assistant (ISA) Several tools available elsewhere VM-generated dumps: Heap Dump Why you d want it: Analyze your Java heap for things like: Large objects Object leaks Determining consumers of Java space

22 Dump Agents You can set up your own dump agents by using the Xdump option. -Xdump enables you to determine what type of dump(s) you want, and when you want them. Dump Agents (con t): -Xdump syntax >>--Xdump: > >--+-help >< +-none events request tokens dynamic what V '---<agent> ' '-:-+-help ' +-none defaults , V V '---+-events=-----<event> ' +-exec=<command> file=<filename> filter=<filter> opts=<options> priority=<0-999> range=<ranges> '-request=<requests>------'

23 Dump Agents (con t): Events/Filters gpf : general protection fault user: SIGQUIT signal abort: SIGABRT signal vmstart: The virtual machine is started. vmstop: The virtual machine stops. Filters on exit code. load: A class is loaded. Filters on class name. unload: A class is unloaded. Filters on class name. throw: An exception is thrown. Filters on exception class name. catch An exception is caught. Filters on exception class name. uncaught: An exception is not caught by the application. Filters on exception class name systhrow: A Java exception is about to be thrown by the JVM. This is different from the 'throw' event because it is only triggered for error conditions detected internally in the JVM. Filters on exception class name. thrstart: A new thread is started. blocked: A thread becomes blocked. thrstop: A thread stops. fullgc: A garbage collection cycle is started. slow: A thread takes longer than 5ms to respond to an internal JVM request. any: Any event is triggered. Dump Agents (con t): Examples To request a system dump when java.lang.noclassdeffounderror is thrown: -Xdump:system:events=throw,filter=java/lang/NoClassDefFoundError To request a system dump and a Java dump when any class in the com/mypackage package is loaded -Xdump:system+java:events=load,filter=com/mypackage/* For more information, see the Java Diagnostics Guide

24 Trace Engine A series of internal VM tracepoints Most used only by service Can trace Java methods To learn details, read the Diagnostics Guide jextract Zips up important files and performs some static analysis. Used for: Preparing a system dump for ISA s DumpAnalyzer Preparing dump data for service (almost always needed in crash scenarios)

25 jextract : What it does libnet.a Zip file Java dump libjava.a Heap dump libjvm.so XML file System dump libjava.a libc.a jextract: How to From QSH, <JAVA_HOME>/jre/bin/jextract <system dump> Replace <JAVA_HOME> with the appropriate value that would be JAVA_HOME for the VM that crashed. For instance, if it was JDK 6, 32bit, run: /QOpenSys/QIBM/ProdData/JavaVM/jdk60/32bit/jre/bin/jextract <system dump> <System dump> is the filename of the system dump generated with the VM crashed. Remember, the filename is going to be in the form core..dmp

26 jextract: How to MUST be run on the same machine that produced the dump (and at the same PTF level!) MUST be run with the same VM (JDK/bit-mode) that produced the dump IBM Support Assistant (ISA) IBM s mechanism for delivering the latest support/debug tools for Java and many IBM products. Tool availability may change over time. Recommended download is ISA Workbench

27 IBM Support Assistant (ISA) Launch ISA Click on First Steps to get the stuff you need IBM Support Assistant (ISA) Open Other to get at the Java related plugins

28 IBM Support Assistant (ISA) Select the plugins for Java Select the plugin for IBM System i IBM Support Assistant (ISA) Under Configuration Tools, you will find AOS. Useful if you need IBM service to get on your system

29 IBM Support Assistant (ISA) Select all the Java tools IBM Support Assistant (ISA) ISA home page! Important updates under Latest News

30 IBM Support Assistant (ISA) Find information very powerful search IBM Support Assistant (ISA) Search finds results for specific targets Click on to review details

31 IBM Support Assistant (ISA) Search Details IBM Support Assistant (ISA) Analyze Problem location of the Java toolset

32 IBM Support Assistant (ISA) Select the tool Click the Launch button (lower left) IBM Support Assistant (ISA) Specify Log name Browse to get your file system

33 IBM Support Assistant (ISA) View GC related performance info IBM Support Assistant (ISA) Click on Memory to see raw data

34 IBM Support Assistant (ISA) Click on Report tab to view recommendations IBM Support Assistant (ISA) Click on Tabbed data tab to view details

35 IBM Support Assistant (ISA) Select a row, view as a graph or raw data IBM Support Assistant (ISA) Click on Line plot tab to view heap grow.

36 IBM Support Assistant (ISA) DumpAnalyzer tool IBM Support Assistant (ISA) Click Browse Specify JEXTRACT output file Create system dump anytime with WRKJVMJOB

37 IBM Support Assistant (ISA) Good stuff under com.ibm.dtfj.analyzer IBM Support Assistant (ISA) Many different tools for diagnosing deadlock and memory issues including native and Java heap

38 IBM Support Assistant (ISA) Good stuff under com.ibm.dtfj.analyzer Click Launch IBM Support Assistant (ISA) Results of the dump

39 IBM Support Assistant (ISA) JVM arguments IBM Support Assistant (ISA) Environment variables

40 IBM Support Assistant (ISA) Memory info IBM Support Assistant (ISA) Java thread info Java and native stacks

41 IBM Support Assistant (ISA) Java Monitors cross-referenced against the threads that hold the monitors IBM Support Assistant (ISA) JITed compiled methods

42 Gathering information for Service ALL java, heap, and system dumps produced!! jextract ed system dump (if a crash) job logs 4700 VLOG s Any general information about how Java is started/used/etc Agenda Key: Session Number: Overview of Interactive Debug 8 Copyright IBM Corporation, All Rights Reserved. This publication may refer to products that are not currently available in your country. IBM makes no commitment to make available any products referred to herein.

43 Finding more information The Diagnostics guide In-depth IT4J debug information. Cross-platform, but not much information on IBM i Can view it online or in PDF form. Each JDK has its own version. Much overlap Java Technology, IBM Style Five articles ew.jsp?search_by=java+technology+ibm+style: IBM Support Assistant (ISA) IBM InfoCenter Trademarks and Disclaimers 8 IBM Corporation All rights reserved. References in this document to IBM products or services do not imply that IBM intends to make them available in every country. Trademarks of International Business Machines Corporation in the United States, other countries, or both can be found on the World Wide Web at Adobe, Acrobat, PostScript and all Adobe-based trademarks are either registered trademarks or trademarks of Adobe Systems Incorporated in the United States, other countries, or both. Intel, Intel logo, Intel Inside, Intel Inside logo, Intel Centrino, Intel Centrino logo, Celeron, Intel Xeon, Intel SpeedStep, Itanium, and Pentium are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States and other countries. Linux is a registered trademark of Linus Torvalds in the United States, other countries, or both. Microsoft, Windows, Windows NT, and the Windows logo are trademarks of Microsoft Corporation in the United States, other countries, or both. IT Infrastructure Library is a registered trademark of the Central Computer and Telecommunications Agency which is now part of the Office of Government Commerce. ITIL is a registered trademark, and a registered community trademark of the Office of Government Commerce, and is registered in the U.S. Patent and Trademark Office. UNIX is a registered trademark of The Open Group in the United States and other countries. Cell Broadband Engine and Cell/B.E. are trademarks of Sony Computer Entertainment, Inc., in the United States, other countries, or both and are used under license therefrom. Java and all Java-based trademarks are trademarks of Sun Microsystems, Inc. in the United States, other countries, or both. Other company, product, or service names may be trademarks or service marks of others. Information is provided "AS IS" without warranty of any kind. The customer examples described are presented as illustrations of how those customers have used IBM products and the results they may have achieved. Actual environmental costs and performance characteristics may vary by customer. Information concerning non-ibm products was obtained from a supplier of these products, published announcement material, or other publicly available sources and does not constitute an endorsement of such products by IBM. Sources for non-ibm list prices and performance numbers are taken from publicly available information, including vendor announcements and vendor worldwide homepages. IBM has not tested these products and cannot confirm the accuracy of performance, capability, or any other claims related to non-ibm products. Questions on the capability of non-ibm products should be addressed to the supplier of those products. All statements regarding IBM future direction and intent are subject to change or withdrawal without notice, and represent goals and objectives only. Some information addresses anticipated future capabilities. Such information is not intended as a definitive statement of a commitment to specific levels of performance, function or delivery schedules with respect to any future products. Such commitments are only made in IBM product announcements. The information is presented here to communicate IBM's current investment and development activities as a good faith effort to help with our customers' future planning. Performance is based on measurements and projections using standard IBM benchmarks in a controlled environment. The actual throughput or performance that any user will experience will vary depending upon considerations such as the amount of multiprogramming in the user's job stream, the I/O configuration, the storage configuration, and the workload processed. Therefore, no assurance can be given that an individual user will achieve throughput or performance improvements equivalent to the ratios stated here. Prices are suggested U.S. list prices and are subject to change without notice. Contact your IBM representative or Business Partner for the most current pricing in your geography.