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Java Garbage Collection

From Ever changing code

Analise GC

Enable GC

Pass following parameters to starting java process

-XX:+PrintGC -XX:+PrintGCDetails -XX:+PrintGCDateStamps -Xloggc:"$CARBON_HOME/repository/logs/gc.log" -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=100 -XX:GCLogFileSize=1024K

Analise

Use GCViewer

git clone https://github.com/chewiebug/GCViewer
cd GCViewer
mvn clean install
java -jar ./target/gcviewer-1.36-SNAPSHOT.jar&  #run in a background
java -jar gcviewer-1.3x.jar gc.log.0;gc.log.1;gc.log.2;gc.log.current summary.csv [chart.png] [-t PLAIN|CSV|CSV_TS|SIMPLE|SUMMARY]

Recommended Throughput should be within 99% range.

Thread Dump

#!/bin/bash

# GIST: bsenduran/thread-analyze.sh 
# https://gist.github.com/bsenduran/02e8bf024fcaaa7707a6bb2321e097a8

# If you get Permission Denied to connecto to process
# try to run just usr/lib/jvm/jdk-oracle/bin/jstack -F <javaPID>
# then rerun this script

# Other sources say you need to disable if you wish to use PTRACE()
# echo 0 > /proc/sys/kernel/yama/ptrace_scope #disables temporarly, default is "1"

# '-l' provides richer info, does not work on all OS, depends on Kernel config


if [ "$#" -ne 3 ]; then
        echo "usage: sh thread-analyze.sh <pid> <number-of-dumps> <interval>"
        echo "   eg: sudo ./thread-analyze.sh 1632 3 10s"
        echo "Avaialble units: s seconds, m for minutes, h for hours, d for days"
        exit
fi

count=$2
for i in `seq 1 $count`;
do
        /usr/lib/jvm/jdk-oracle/bin/jstack -F    $1 > thread_dump_`date "+%F-%T"`.txt &
#       /usr/lib/jvm/jdk-oracle/bin/jstack -F -l $1 > thread_dump_`date "+%F-%T"`.txt &
        ps --pid $1 -Lo pid,tid,%cpu,time,nlwp,c > thread_usage_`date "+%F-%T"`.txt &
if [ $i -ne $count ]; then
        echo "sleeping for $3 [$i]"
        sleep $3
fi
done