Basic Steps and Features Walk-through

Transcription

1 Welcome to the SAP Memory Analyzer SAP Memory Analyzer: Basic Steps and Features Walk-through SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 1

2 Basic Steps with SAP Memory Analyzer (1) Get Heap Dump IOIOII IOIIOI OIOIO IIOIIOI (2) Parse Heap Dump (3) Analyze Heap Dump SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 2

3 (1) Get Heap Dump Available for which JDKs? Sun, SAP and HP JDK >= 1.4.2_12 and >= 1.5.0_7 Therefore applies to SAP: 640, 04s, 710, CE Windows, Solaris, HP-UX IBM JDK has its own proprietary format. You need to use IBM s own tools. HPROF Binary Heap Dump IOIOII IOIIOI OIOIO IIOIIOI Heap dump contains a snapshot of all objects that are alive at one point in time. All Objects Class, fields, primitive values and references All Classes ClassLoader, name, super class, static fields All ClassLoaders Defined classes Garbage Collection Roots Objects defined to be reachable by the JVM t How to get an heap dump? On Out Of Memory -XX:+HeapDumpOnOutOfMemoryError On Ctrl-Break -XX:+HeapDumpOnCtrlBreak AGENT LIB JMAP JCONSOLE JVMMON SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 3

4 (2) Parse Heap Dump A1S Size: S Objects SAP Memory Analyzer parses heap dumps on first open. Preprocessing allows faster analysis on smaller machines. IOIOII IOIIOI OIOIO IIOIIOI 64 bit machines only needed for dumps with > 20 million objects or sizes > 2 GB. Once parsed, analyze the dump on 32 bit developer machines it opens instantly. t SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 4

5 (3) Analyze Heap Dump Get Heap Dump t IOIOII IOIIOI OIOIO IIOIIOI Parse Heap Dump Analyze Heap Dump Get an Overview Find Big Chunks Check Content Identify Holder total number of objects total heap size class histogram SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 5

6 (3) Analyze Heap Dump Get an Overview t IOIOII IOIIOI OIOIO IIOIIOI Get an Overview total number of objects total heap size class histogram SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 6

7 Snapshot Info and Class Histogram Number of objects The histogram lists per class the number of objects and their total shallow size. Anything but char[] is usually suspicious. Number of classes Number of class loaders Look out for accumulation of classes from the same package. Total heap size SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 7

8 Class Histogram Grouping Group classes by class loader SAP Memory Analyzer extracts the names of the deployment units SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 8

9 (3) Analyze Heap Dump Find Big Chunks t IOIOII IOIIOI OIOIO IIOIIOI Get an Overview Find Big Chunks total number of objects total heap size class histogram SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 9

10 Find Big Single Objects See Object Inspector for object details and field values. Open the Dominator Tree to see the biggest distinct single objects Retained size = memory freed if this object would be garbage collected This one HashMap keeps ~160MB alive, which are 6% of the total heap! Look out for instances of the same class! Even better: group by classes (see next slide). SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 10

11 Find Big Groups of Objects Group by classes to find big chunks kept alive by instances of one class 398 instances retain ~430MB, i.e. 15%! 4 classes in the.*sushi.* and.*sashimi.* packages consume 1.1 GB, i.e. 40%! SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 11

12 (3) Analyze Heap Dump Check Content t IOIOII IOIIOI OIOIO IIOIIOI Get an Overview total number of objects total heap size class histogram Find Big Chunks Check Content SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 12

13 Looking Into Big Memory Chunks Drill down in the dominator tree: What is kept alive by the objects? Using the context menu to show the histogram of the retained set, i.e. all objects kept alive grouped by classes. Check outbound references to understand the data structures. SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 13

14 (3) Analyze Heap Dump Identify Holder t IOIOII IOIIOI OIOIO IIOIIOI Get an Overview Find Big Chunks Check Content Identify Holder total number of objects total heap size class histogram SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 14

15 Paths From GC Roots The orange dot indicates a garbage collection root. At the end of the line you see the reason, e.g. it could have been used as local variable. For all GC Roots associated with a thread (Local Variable, Busy Monitor, JNI Local), we also show the thread. SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 15

16 (3) Analyze Heap Dump Get Heap Dump t IOIOII IOIIOI OIOIO IIOIIOI Parse Heap Dump Analyze Heap Dump Get an Overview Find Big Chunks Check Content Identify Holder total number of objects total heap size class histogram SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 16

17 Advanced Features Execute SQL-like queries on the objects in the heap dump with the build-in OQL. Use the console to run special purpose queries implemented in commands. SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 17

18 SAP NetWeaver Features SAP Memory Analyzer extracts 640, NW04s and 710 sessions and displays domains, ids and size in one view. The Cache view shows the content of all cache regions. SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 18

19 Feature Overview Overview Total heap size Total number of objects/classes Class histogram Histogram by ClassLoader Single object Finding big chunks of memory Check the Dominator Tree TOP_CONSUMERS Groups of objects Finding big chunks of memory Grouping in Dominator Tree TOP_CONSUMERS ARR_SZ_HISTOGRAM LOCAL_VARS OQL Content Analysis Expand/explore the Dominator Tree Analyze the retained set Object outbound references/object inspector OQL Content Analysis Object lists/histograms Analyze the retained set Class-level outbound references OQL Holder Analysis Object inbound references Paths from the GC roots Holder Analysis Class-level inbound references Multiple paths from the GC roots Immediate Dominators SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 19

20 Resources SAP SDN Wiki SAP AG 2007, Memory Analysis with SAP Memory Analyzer / 20