Embark on a journey into the depths of java.lang.OutOfMemoryError as we unravel its complex nature. Discover the nine distinct faces of this memory-related challenge and gain valuable insights into their unique causes and solutions. This session equips you with the knowledge, tools, and techniques needed to troubleshoot and conquer OutOfMemoryError in all its forms, ensuring smoother, more efficient Java applications.

1. 1

2. Does Java process memory utilization go beyond –Xmx?
2
–XX:MaxMetaspaceSize
-Xmx
Young Old
Metaspac
e
Threads JNI misc
GC
Direct
Buff
Code
Cach
e
Heap Memory Native Memory
Java Process Memory

3. 3
Demo
OutOfMemoryError

4. 4
How to know the type of OutOfMemoryError?
java.lang.OutOfMemoryError: <type>

5. 5
Java Heap Space
Metaspac
e
Threads JNI misc
GC
Direct
Buff
Code
Cach
e
Heap Memory Native Memory
JVM Memory
Most common type

6. 6
GC Behavior of a Healthy Application
- Full Garbage Collection Event

7. 7
GC Behavior of Acute Memory Leak
- Full Garbage Collection Event

8. 8
GC Behavior when there is a Memory Leak
- Full Garbage Collection Event

9. 9
How to study GC Behavior?
-XX:+PrintGCDetails -XX:+PrintGCDateStamps -Xloggc:<file-path>
Till Java 8
-Xlog:gc*:file=<file-path>
From Java 9
Enable GC logs (always)
Almost zero overhead

10. 10
GCeasy
GC Log Analysis Demo

11. 11
How to capture Heap Dumps?
8 options: https://blog.heaphero.io/2017/10/13/how-to-capture-java-heap-dumps-7-options/

12. 1. GC Log
10. netstat
12. vmstat
2. Thread Dump
9. dmesg
3. Heap Dump
6. ps
8. Disk Usage
5. top 13. iostat
11. ping
14. Kernel Params
15. App Logs
16. metadata
4. Heap Substitute
7. top -H
12
Open-source script:
https://github.com/ycrash/yc-data-script
360° Troubleshooting artifacts

13. 13
HeapHero
Heap Dump Analysis Demo

14. 14
OutOfMemoryError: Java Heap Space
Causes
1. Increase in Traffic Volume
2. Memory leak due to
buggy code
Solutions
1. Fix Memory Leak in the
code
2. Increase heap size (-Xmx)
Artifacts
1. Garbage Collection Log
2. Heap Dump
Tools
1. GCeasy (GC log
analysis)
2. HeapHero
3. Eclipse MAT
4. JProfiler

15. 15
GC overhead limit exceeded
Metaspac
e
Threads JNI misc
GC
Direct
Buff
Code
Cach
e
Heap Memory Native Memory
JVM Memory

16. 16
OutOfMemoryError: GC overhead limit exceeded
Diagnosis: Same as ‘Java Heap Space’ 

17. 17
Requested array size exceeds VM limit
Young Old
Metaspac
e
Threads JNI misc
GC
Direct
Buff
Code
Cach
e
Heap Memory Native Memory
JVM Memory

18. 18
Demo
OutOfMemoryError: Requested array size exceeds VM
limit

19. 19
OutOfMemoryError: Requested array size exceeds VM limit
Causes
1. Allocated array larger than
heap size
Solutions
1. Fix Memory Leak code
2. Increase heap size (-Xmx)
Artifacts
1. Application Log or std error
Tools

20. 20
Metaspace
Young Old Threads JNI misc
GC
Direct
Buff
Code
Cach
e
Heap Memory Native Memory
JVM Memory

21. 21
Demo
OutOfMemoryError: Metaspace

22. 22
Metaspace Memory Leak
- Full Garbage Collection Event

23. 23
OutOfMemoryError: Metaspace
Causes
1. Creating large number of
Dynamic classes (Java
Reflection, Groovy type of script
languages)
2. Loading large number of Classes
3. Loading large number of
Classloaders
Solutions
1. Fix Memory Leak code
2. Increase -XX:MetaspaceSize
and
-XX:MaxMetaspaceSize.
Artifacts
1. Java 8 & below: java
{app_name} -verbose:class
2. Java 9 & above: java
{app_name} -
Xlog:class+load=info:<filena
me>
3. jcmd {pid} GC.class_histogram
4. Heap Dump
Tools
1. Gceasy (GC log analysis)
2. HeapHero
3. Eclipse MAT
4. JProfiler
5. JHat

24. 24
Permgen space
Young Old Threads JNI misc
GC
Direct
Buff
Code
Cach
e
Heap Memory Native Memory
JVM Memory
Happens only in Java 7 & below

25. 25
OutOfMemoryError: Permgen Space
Diagnosis: Same as ‘Metaspace’ 

26. 26
Unable to create new native threads
Young Old
Metaspac
e
JNI misc
GC
Direct
Buff
Code
Cach
e
Heap Memory Native Memory
JVM Memory

27. 27
Real Case Study
Slowdown in a Major Financial Institution’s Middleware
http://fastthread.io/my-thread-report.jsp?p=c2hhcmVkLzIwMTcvMDMvMTQvLS10aHJlYWREdW1wLTIudHh0LS0xMi0yOC0zMw==&s=t

28. 28
OutOfMemoryError: Unable to create new native
threads
Causes
1. Threads are leaking
Solutions
1. Fix thread leak
2. Increase the Thread Limits Set
at Operating System(ulimit –u)
3. Reduce Java Heap Size
4. Kills other processes
5. Increase RAM capacity
6. Reduce thread stack size (-Xss).
Note: can cause
Artifacts
1. Thread Dump
Tools
1. FastThread
2. Text Editor

29. 29
Direct buffer memory
Young Old
Metaspac
e
Threads JNI misc
GC
Code
Cach
e
Heap Memory Native Memory
JVM Memory
Becoming Prevasive in modern Spring Boot Frameworks

30. 30
OutOfMemoryError: Direct buffer memory
Causes
1. Increase(or Leak) in direct buffers
usage
a. java.nio package
b. Moving from Spring
RestTemplate to WebClient
c. Image Processing Libraries
d. Networking Libraries
e. Some JDBC Drives
Solutions
1. Fix Memory Leak code
2. Increase -
XX:MaxDirectMemorySize
3. Upgrade to Java 17 (There some
issues in Java 11)
Artifacts
1. App Log or Std error
2. Native Memory Tracking
Tools

31. 31
Kill process or sacrifice child
JVM Kernel
X

32. 32
Real Case Study
Intermittent HTTP 502 errors in AWS EBS Service

33. EBS Architecture
33

34. Clue: Nginx Error
34

35. 35

36. 36
OutOfMemoryError: Kill process or sacrifice child
Causes
1. Lack of RAM capacity
2. High Memory utilization by
other processes
3. Memory Leak in the code
Solutions
1. Kill other processes
2. Increase RAM capacity
3. Fix Memory Leak in the code
Artifacts
1. Dmesg
2. GC Log
3. Heap Dump
4. Native Memory Tracking
Tools
1. HeapHero
2. Eclipse MAT
3. yCrash

37. 37
Reason stack_trace_with_native_method
Young Old
Metaspac
e
Threads misc
GC
Direct
Buff
Code
Cach
e
Heap Memory Native Memory
JVM Memory

38. 38
OutOfMemoryError: Reason stack_trace_with_native_method
Don’t worry, if you are not using JNI 

39. Ram Lakshmanan ram@tier1app.com
@tier1app https://www.linkedin.com/company/ycrash
This deck will be published in:
https://blog.heaphero.io
If you want to learn more …
39
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FRIENDS