Is it tuning the garbage collector? Writing clean(er) code? No, the first step is understanding what’s going on in your application! Performance tuning starts with analysis, and JDK tools can help you gain insights on classes and threads and can perform live GC analysis or heap dump postprocessing: jcmd, jconsole, jstat, jmap and jfr. We’ll examine the functional visibility areas essential to Java and how these tools provide that information. Moreover, will discuss options on how to integrate information gathered from these tools with widespread monitoring systems like Prometheus. After this talk, you will be ready to understand what your application spends time on and why so you can start improving its perform

1. A Glance at
The Java Performance
Toolbox

3. Java Champion Alumni, Certified Architect
Senior Developer Advocate at Oracle
Passionate about solving complex scenarios involving
Java and Kubernetes.
ammbra1508 ammbra1508.mastondon.social

4. What does application
performance mean?

5. Performance experienced by end-
users
Computational resources used by
the application

6. Performance Metrics
CPU Usage
Memory Usage
Error rates
User satisfaction (Apdex scores)
Average response time
Request rates
Latency and uptime
Throughput

8. More Questions Using Java Applications in
Containers
• Which JDK tools help you create container images with only what is needed at
runtime?
• How to run the JDK tools in containers and proxy their output?
• Which tools help you fine tune the JVM flags and keep application overhead at
minimum?
• How to capture performance relevant JVM and application events?
• How to correlate data from JVM monitoring tools with the one from tools like
Prometheus, Grafana?

9. Which tools help you create
container images with only what
is needed at runtime?

11. Tools to build an OCI Compliant Image
• Docker build
• Buildpacks
• Jib
• kaniko
• buildah
• s2i
• And many more J

12. The Good Old Dockerfile

13. The Good Old Dockerfile
Use a small base image

14. The Good Old Dockerfile
Use a small base image
Create images with common layers

15. The Good Old Dockerfile
Use a small base image
Install only what is strictly needed
Create images with common layers

16. JDK tools that shape
efficient Java Runtimes for
Container Images

17. jlink
JEP 282 “Link time is an opportunity to do whole-world optimizations that are
otherwise difficult at compile time or costly at run-time”
jlink: Command Line Tool to Link Modules
• Modules in a jimage file
• Generate runtime images

18. Jlink packaging
Legacy JDK image
JDK > 9 generated image
bin jre lib
bin conf ……..
Modular runtime image
jlink

19. Maintain The Good Old Dockerfile with jlink
The runtime stage build
• From a JDK base image
• Create your own custom JRE with jlink

20. Maintain The Good Old Dockerfile with JLink
The runtime stage build
• From a JDK base image
• Create your own custom JRE with jlink
The application stage build
• From an OS base image
• Copy the custom JRE from the runtime stage build
• Copy the artifacts needed by your application
• Run the application

21. The Runtime Stage Build

22. The Runtime Stage Build
jdeps --ignore-missing-deps -q -recursive
--multi-release 21 --print-module-deps
--class-path 'target/libs/*'
target/spring-todo-app.jar

23. The Runtime Stage Build
Exclude man pages and header files

24. The Runtime Stage Build
Enable compression of resources:
0: No compression
1: Constant string sharing
2: ZIP

25. The Application Stage Build
Copy the custom JRE

26. The Application Stage Build
Copy the artifacts needed by your application

27. The Application Stage Build
Run the application

28. How about fine tuning
JVM Flags?

29. Conserving Dynamic Footprint by
Minimizing Java Heap Size
Start by looking at the JVM ergonomics

30. Conserving Dynamic Footprint by
Minimizing Java Heap Size
Start by looking at the JVM ergonomics
At initialization of the virtual machine, the entire space for the heap is reserved.
Eg: setting for minimum and maximum heap size: -Xms768m -Xmx768m

31. Conserving Dynamic Footprint by
Minimizing Java Heap Size
Start by looking at the JVM ergonomics
At initialization of the virtual machine, the entire space for the heap is reserved.
Eg: setting for minimum and maximum heap size: -Xms768m -Xmx768m
Minimize Java heap size by lowering the values of the options:
• -XX:MaxHeapFreeRatio (default value is 70%)
-XX:MinHeapFreeRatio (default value is 40%)
• Eg:-XX:MinHeapFreeRatio=10 -XX:MaxHeapFreeRatio=70

32. What if the problem is not
the amount of resources
allocated to/by the JVM?

33. Tracking Native Memory With Jcmd
Add jdk.jcmd module

34. Tracking Native Memory With Jcmd
Overusing jcmd to send diagnostic commands can affect the performance of the VM.

35. Tracking Native Memory With Jcmd
Overusing jcmd to send diagnostic commands can affect the performance of the VM.
-XX:NativeMemoryTracking={off|summary|detail}
• kubectl set env deployment/app JDK_JAVA_OPTIONS=“-XX:NativeMemoryTracking=summary”
• Please consider that having NMT enabled can add application performance overhead.

36. Tracking Native Memory With Jcmd
Overusing jcmd to send diagnostic commands can affect the performance of the VM.
Add -XX:NativeMemoryTracking={off|summary|detail} to JDK_JAVA_OPTIONS
Create a native memory baseline
kubectl exec pod_name –it --/bin/bash -c "jcmd llvmid VM.native_memory baseline"

37. Tracking Native Memory With Jcmd
Overusing jcmd to send diagnostic commands can affect the performance of the VM.
Add -XX:NativeMemoryTracking={off|summary|detail} to JDK_JAVA_OPTIONS
Create a native memory baseline
kubectl exec pod_name –it --/bin/bash -c "jcmd llvmid VM.native_memory baseline"
Create a native memory summary diff
kubectl exec pod_name –it --/bin/bash -c "jcmd llvmid VM.native_memory summary.diff"

38. Performance and
Resource Consumption
Overview information about the Java VM and
monitored values.
Information about memory use.
Information about thread use.
Information about class loading.
Information about the Java VM.
Information about MBeans

39. Get Statistics About
Running Java Processes

40. Obtain Statistics with jstat and jmap
Obtain statistics about garbage collectors by running jstat
kubectl exec pod_name –it --/bin/bash -c "jstat -gcutil llvmid 500 50"

41. Obtain Statistics with Jstat and Jmap
Obtain statistics about garbage collectors by running jstat
kubectl exec pod_name –it --/bin/bash -c "jstat -gcutil llvmid 500 50"
Print heap summaries
kubectl exec pod_name –it --/bin/bash -c "jmap -histo llvmid"

42. Capture Performance
Relevant JVM And
Application Events

43. When to Use Profiling
“To consume the data today, a user must start a recording, stop it, dump the
contents to disk and then parse the recording file. This works well for
application profiling, where typically at least a minute of data is being
recorded at a time, but not for monitoring purposes.“
source: JEP 349

44. Add JFR To Your Container Image
Add jdk.jfr module

45. How to use JFR
Enable JFR in JDK_JAVA_OPTIONS
kubectl set env deployment/app JDK_JAVA_OPTIONS=“--XX:StartFlightRecording:..”
For example, start a time fixed recording with default profile
-XX:StartFlightRecording=delay=10s,duration=10m,name=Default,settings=default
Use the diagnostic command:
kubectl exec pod_name –it --/bin/bash -c "jcmd llvimd JFR.start…"

46. Monitor and React
…..
AppTarget 1
AppTarget 2
AppTarget n
Prometheus server
Pull metrics
Pull metrics
Pull metrics
Gathering metrics
Visualizing metrics
Alerting

47. Streaming selected metrics to your
monitoring service
Where to Use JFR
Event Streaming

48. Stream selected metrics to your
monitoring service
Send an average, min, max, etc of a metric
Where to Use JFR
Event Streaming

49. Stream selected metrics to your
monitoring service
Send an average, min, max, etc of a metric
Expose JFR data through other
management APIs
Where to Use JFR
Event Streaming

50. Make your settings by extending
jdk.jfr.SettingControl
Recording Custom
JFR Events

51. Make your settings by extending
jdk.jfr.SettingControl
Create your custom event by extending
jdk.jfr.Event
Recording Custom
JFR Events

52. Recording Custom
JFR Events
Make your settings by extending
jdk.jfr.SettingControl
Create your custom event by extending
jdk.jfr.Event
Register the custom settings in your custom
event via
@jdk.jfr.SettingsDefinition

53. Recording Custom Events in Spring Boot
(example)
Capture the custom JFR events in a dedicated filter and register it

54. Recording Custom Events in Spring Boot
(example)
Listen the custom JFR events and record their duration

55. Takeaways
Use jlink to create a
minimal custom
JRE.
Send diagnostic
commands to a
running JVM via
jcmd.
Inspect
performance
statistics
Profile your
application with jfr.
Stream preferred
JVM metrics to
your monitoring
service with JFR
Event Streaming
API.

56. Thank You!
https://github.com/ammbra/performance-glance

57. Useful Links
• Article https://www.javaadvent.com/2022/12/a-sneak-peek-at-the-java-performance-toolbox.html
• Tools https://docs.oracle.com/en/java/javase/21/docs/specs/man/index.html
• jlink https://dev.java/learn/jlink/
• Troubleshoot Memory Leaks: https://docs.oracle.com/en/java/javase/21/troubleshoot/troubleshooting-memory-
leaks.html
• JFR Runtime guide : https://docs.oracle.com/javacomponents/jmc-5-4/jfr-runtime-guide/about.htm#JFRUH170
• Innovative JFR use by @gunnarmorling: https://www.morling.dev/blog/finding-java-thread-leaks-with-jdk-flight-
recorder-and-bit-of-sql/
• @gunnarmorling article on custom JDK Flight Recorder Events
• Great intro by @BillyKorando https://www.youtube.com/watch?v=K1ApBZGiT-Y
• Stack walker episode by @BillyKorando: https://inside.java/2023/05/14/stackwalker-02/