bernhard.hensler.net » java http://bernhard.hensler.net/blog Mon, 28 Jun 2010 13:52:02 +0000 http://wordpress.org/?v=2.9.2 en hourly 1 how to enable and analyze verbose garbage collection http://bernhard.hensler.net/blog/how-to-enable-and-analyze-verbose-garbage-collection/ http://bernhard.hensler.net/blog/how-to-enable-and-analyze-verbose-garbage-collection/#comments Thu, 27 Aug 2009 08:16:11 +0000 bernhard http://bernhard.hensler.net/blog/?p=1474 In Web applications, memory utilization can impact system performance significantly. One of the most common memory problems is memory leak, which causes severe performance degradation. In theory, memory leaks should not happen in Java™ because it has Garbage Collection (GC). However, GC only cleans up unused objects that are not referenced anymore. Therefore, if an object is not used, but is still referenced, GC does not remove it, which leads to memory leaks. Beside memory leaks, other memory problems that you might encounter are memory fragmentation, large objects, and tuning problems. In many cases, these memory problems can cause the application server to crash. Many users first notice that application server performance gradually declines, and eventually crashes with OutOfMemory exceptions.

[SinglePic not found] Enabling verbose Garbage Collection for WebSphere based Application servers, is simple (see image). After a restart garbage collection is logged in native_stderr.log:

[SinglePic not found]

There are many tools for verbose GC log analysis, these tools can abstract useful information, and illustrate the trend of JVM heap size usage over time as the following. [SinglePic not found]

IBM Pattern Modeling and Analysis Tool for Java Garbage Collector (PMAT) parses the IBM verbose GC trace and provides a comprehensive analysis of the Java heap usage. It then recommends key configurations by first executing a diagnosis engine and then employing a pattern modeling algorithm in order to make recommendations to optimize the Java heap usage for a given JVM cycle.

source for this article
PMAT
JDK Diagnosis

see also here

]]> http://bernhard.hensler.net/blog/how-to-enable-and-analyze-verbose-garbage-collection/feed/ 1 how to generate and analyze a WebSphere heapdump http://bernhard.hensler.net/blog/how-to-generate-and-analyze-a-websphere-heapdump/ http://bernhard.hensler.net/blog/how-to-generate-and-analyze-a-websphere-heapdump/#comments Fri, 21 Aug 2009 18:32:59 +0000 bernhard http://bernhard.hensler.net/blog/?p=1298 ./was_profile/bin/wsadmin.sh -conntype SOAP -host wcl.private.lan -port 10033 -user wasadmin -password passw0rd

WASX7209I: Connected to process “WebSphere_Portal” on node wcl using SOAP connector; the type of process is: unManagedProcess; WASX7029I: For help, enter: “$Help help”

wsadmin> set jvm [$AdminControl completeObjectName type=JVM,process=WebSphere_Portal,*]

WebSphere:name=JVM,process=WebSphere_Portal,
platform=dynamicproxy,node=wcl,j2eeType=JVM,
J2EEServer=WebSphere_Portal,version=6.0.2.17,
type=JVM,mbeanIdentifier=JVM,cell=wcl

wsadmin>$AdminControl invoke $jvm generateHeapDump
wsadmin>$AdminControl invoke $jvm dumpThreads

IBM’s support assistant (ISA) is an Eclipse based tool with quite a number of plugins to analyze heapdumps – a good developerworks article can be found here (part I) and here (part II).

To analyze WebSphere Portal performance issues, although this document is applicable to isolate performance problems around Java based application servers in general , see here.

see also here

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