1.
Elastic JVM
Automatic Vertical Scaling
of the Java Heap

2.
Java Can Be Greedy!

3.
Java Memory Consumption Problems

4.
Java Memory Consumption Problems
Difficult to Scale
Costs Too Much
Consumes a Lot

5.
Technical Reasons to
Make Java Flexible

6.
Horizontal Scaling Is Not Always a Solution

7.
Better Elasticity & Density with Containers

8.
Reducing Memory Usage to Speed Up Live Migration
https://www.youtube.com/watch?v=HfN4L6RFL10

9.
Overpayment for
Java Cloud Hosting

10.
Pay per Usage as for Electricity

11.
Reserved vs Consumed
Real statistics of defined limits and actually consumed resources
Wasted Resources Used Resources

12.
Are JVM-Based
Applications Fully
Container-Ready?

13.
Blockers for JVM Automatic Vertical Scaling
Unreleased Heap Memory Restart for Xmx Resize

14.
Garbage Collectors
Testing

15.
G1 Garbage Collector: Fast Memory Usage Growth
java -XX:+UseG1GC -Xmx2g -Xms32m -jar app.jar 0
Memory grew from 32 MB to 1 GB in 25 seconds
https://github.com/jelastic/java-vertical-scaling-test

16.
G1: Medium Memory Usage Growth
java -XX:+UseG1GC -Xmx2g -Xms32m -jar app.jar 10
Memory grew from 32 MB to 1 GB in 90 seconds during 4 cycles

17.
G1: Slow Memory Usage Growth
java -XX:+UseG1GC -Xmx2g -Xms32m -jar app.jar 100
Memory grew from 32 MB to 1 GB with delta time growth of about 300 seconds

18.
G1: Aggressive Heap = No Vertical Scaling
java -XX:+UseG1GC -Xmx2g -Xms2g
or
java -XX:+UseG1GC -Xmx2g -XX:+AggressiveHeap

19.
Parallel Garbage Collector
java -XX:+UseParallelGC -Xmx2g -Xms32m -jar app.jar 10
The unused but committed RAM is never released back to OS

20.
Serial Garbage Collector
java -XX:+UseSerialGC -Xmx2g -Xms32m -jar app.jar 10
It requires 4 Full GC cycles to release all unused resources

21.
ConcMarkSweep Garbage Collector
java -XX:+UseConcMarkSweepGC -Xmx2g -Xms32m -jar app.jar 10
It requires 4 Full GC cycles to release all unused resources

22.
Calling Full GC On-Time
https://github.com/jelastic-jps/java-memory-agent
1. Full GC is not triggered automatically and must be executed explicitly
2. Can lead to significant performance degradation
Workaround:
inject an agent which monitors the memory usage and calls System.gc()
periodically:
-javaagent:jelastic-gc-agent.jar=period=300,debug=true

23.
Shenandoah Garbage Collector
java -Xmx2g -Xms32m -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC
-XX:ShenandoahUncommitDelay=1000 -XX:ShenandoahGuaranteedGCInterval=10000 -jar app.jar 10
It releases unused RAM back to OS on the fly without Full GC calls
https://wiki.openjdk.java.net/display/shenandoah/Main

24.
The Z Garbage Collector
java -XX:+UnlockExperimentalVMOptions -XX:+UseZGC
http://cr.openjdk.java.net/~pliden/slides/ZGC-FOSDEM-2018.pdf

25.
OpenJ9
Command-line options to enable automatic vertical scaling:
● -XX:+IdleTuningGcOnIdle
● -XX:+IdleTuningCompactOnIdle
● -XX:IdleTuningMinIdleWaitTime=<secs>
● Low memory footprint
● Fast startup time
● High application throughput
● Smoother ramp-up in the cloud
https://www.eclipse.org/openj9/

26.
New Patch for
Garbage-First
Collector in
OpenJDK 9

27.
Started in 2011
● Initiated investigation (at first, worked out only with SerialGC)
● Built cloud business model on vertical scaling
● Started to promote in the community

28.
Credits To
● Ruslan Synytsky, Tetiana Fydorenchyk: Jelastic
● Rodrigo Bruno, Paulo Ferreira: INESC-ID / Instituto Superior Técnico,
University of Lisbon
● Jia Rao: The University of Texas at Arlington
● Hang Huang, Song Wu: Huazhong University of Science and Technology
● Thomas Schatzl: Oracle

29.
Timely Reduce Unused Committed Memory
Make the G1 garbage collector automatically give back Java heap memory
to the operating system when idle
● G1PeriodicGCInterval
● G1PeriodicGCSystemLoadThreshold
● G1PeriodicGCInvokesConcurrent
http://openjdk.java.net/jeps/8204089

30.
Dynamic Max Memory Limit
Allow a user to increase / decrease the amount of Java heap memory
available to the application at runtime http://openjdk.java.net/jeps/8204088
jinfo -flag CurrentMaxHeapSize=1g <java_pid>

31.
Extra Tips Not to
Lose Your Memory

32.
Improving Memory Compaction
-XX:-ShrinkHeapInSteps
● disable 4 full GC cycles
● release unused RAM resources faster
● minimize the Java heap size usage in applications with variable load

33.
Tracking Native Non-Heap Memory Usage
-XX:NativeMemoryTracking=summary
5-10% performance hit if this option is enabled
http://trustmeiamadeveloper.com/2016/03/18/where-is-my-memory-java/

34.
Java SE Support for Docker CPU and RAM Limits
CPU (Java SE 8u131+)
-XX:ParalllelGCThreads or
-XX:CICompilerCount
if not specified → Docker CPU limit
RAM
Java heap via -Xmx
if not specified →
-XX:+UnlockExperimentalVMOptions
-XX:+UseCGroupMemoryLimitForHeap
https://jelastic.com/blog/java-and-memory-li
mits-in-containers-lxc-docker-and-openvz
https://blogs.oracle.com/java-platform-group
/java-se-support-for-docker-cpu-and-memor
y-limits

35.
Make Your Java Elastic
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