JVM performance profiling (有待整理)

Agenda

memory model

3 parts: heap, permgen (method area) , thread stack(pointer, local var)

heap: young and old generation ?? permanent generation 

young: eden, fromspace(surviror1), tospace(surironr2)

== quoted ==

To get the clear memory diagram:http://blog.pointsoftware.ch/index.php/under-the-hood-runtime-data-areas-javas-memory-model/

http://www.yourkit.com/docs/kb/sizes.jsp

http://www.slideshare.net/gengmao/inside-the-jvm-memory-management-and-troubleshooting  

PermGen

The method area is also known as the permanent generation space (PermGen). Allclass data are loaded into this memoryspace. This includes the field and method data and the code for the methods andconstructors

Heapmemory

Sinceobjects are stored in the heap part it is worth to have a closer look. The heapspace itself is again separated into several spaces:

-Young generation  with eden and survivor space

-Old Generation with tenured space

Eachspace harbors objects with different life cycles:

-New/short-term objects are instantiated in theeden space.

-Survived/mid-term objects are copied from theeden space to the survivor space.

- Tenured/long-term objects arecopied from the survivor to the old generation space.

== unquoted ==

jvm setting

GC algorithm: serial, ... etc, MaxNewSize,  MaxSize ,  there is recommendation online, client side, server side and diff platform.

JavaOne: best heap percent :43% ??

tunning concerns

availablility  , throughput, latency and responsiveness, memory footprint (100 txn need how many mem?), startup time

real time profiling

Remote
Add JMX parameter to bootstrap script


$JAVA_HOME/bin/java ${GC_OPTS}
-Dcom.sun.management.jmxremote  
-Dcom.sun.management.jmxremote.port=9010
-Dcom.sun.management.jmxremote.local.only=false
-Dcom.sun.management.jmxremote.authenticate=false
-Dcom.sun.management.jmxremote.ssl=false
-classpath $PROJ_CLASSPATH ${BOOTSTRAPPER} ${PARAMETER}

Local 

VisualVM/Jconsole is able to detect the running JAVA application process id..

http://www.gamlor.info/wordpress/2011/09/visualvm/

Eclipse for VisualVM (https://visualvm.java.net/eclipse-launcher.html)

JMX profile ?! - linux svr profile , like shell

server port number?!  - need ask server team

Will it cause the app slowness? - yes, occupy CPU

post gc analysis

Enable the verbose:gc option in the bootstrap script

-verbose:gc

-Xms512m -Xmx1024m

-XX:+PrintGCTimestamps

-XX:+PrintGCDetails

-Xloggc:./${GC_LOG}

After the log file generated, you can use the tool to analyse. - GC Histogram Tool

All GC

Young GC - GC in young generation ?

Full GC - 

Good tips:

Eclipse plugin center - for you to goto there via company proxy, 

1. check from stackoverflow site - Add parm into eclipse.ini  ;

2. disable socket proxy port

Websphere JVM profiling on app server

Ask WAS team to install a was plugin into for monitor