There are more than 600 arguments that you can pass to JVM only for garbage collection and memory. It's way too many arguments for anyone to digest and comprehend. In this session, we will highlight seven essential JVM parameters that will improve the performance of your application.

2. -Xmx
2
Maximum Heap Size

3. Young: Newly created Objects
Old: New objects that survived
minor GC promoted here
Metaspace: Classes, Methods,
metadata
Others Description
Thread Stacks Each thread has a separate memory space. Controlled by -
Xss
Garbage
Collection
Thread, Memory to store GC info
Code Generation Converting bytecode to native code
Socket Buffers TCP Connections (Receive buffer ~37k, Send Buffer ~2.5k)
JNI JNI program also allocate memory
Does Java process memory utilization go beyond –Xmx?
Young old metaspace others
3
–XX:MaxMetaspaceSize
-Xmx

4. Large heap size with less JVM instances or Small heap size with large JVM instances?
-Xmx2g
Heap size arguments for Containers: -XX:MaxRAMPercentage
Benefits of setting initial & max heap size to same value
1. -Xmx
4

5. 5
-XX:MaxMetaspaceSize
Maximum MetaSpace Size

6. -XX:MaxMetaspaceSize=256m
2. –XX:MaxMetaspaceSize
6

7. -Xss
7
Thread Stack Size

8. main( )
a( )
b( )
c( )
x=1
y*
z=2.11
public class SimpleExample {
public static void main(String args[]) {
a();
}
public static void a() {
int x = 1;
b();
}
public static void b() {
Car y = new Car();
c();
}
public static void c() {
float z = 2.11f;
}
}
Thread’s stack
Young old metaspace
car
-Xmx
-Xss
-
XX:MaxMetaspaceSiz
e
car
metada
How is Java program executed?
8

9. -Xss256k
Are Java threads – memory efficient?
JVM Version Thread stack size
Sparc 32-bit JVM 512k
Sparc 64-bit JVM 1024k
x86 Solaris/Linux 32-bit
JVM
320k
x86 Solaris/Linux 32-bit
JVM
1024k
Windows 32-bit JVM 320k
Windows 64-bit JVM 1024k
3. -Xss
9

10. 10
GC Algorithm
& it related settings

11. What is Garbage?
HTTP Request
Objects
Memory
Garbage
11

12. 3-4 Decades ago
Developer
Writes code to Manually evict Garbage
JVM
Automatically evicts Garbage
Now
How are objects Garbage Collected?
Evolution: Manual -> Automatic
12

13. Automatic GC sounds good right?
Yes, but for
GC pauses CPU consumption
Success Stories of GC tuning
13

14. Case study: Large Automobile Manufacturer
GC Tuning improves entire app’s response
time
https://blog.gceasy.io/2022/08/25/automobile-company-optimizes-performance-using-
gceasy/
Avg response time (secs) Transactions > 25 secs
(%)
Baseline 1.88 0.7
GC settings #2 1.36 0.12
GC settings #3 1.7 0.11
GC settings #4 1.48 0.08
GC settings #5 2.045 0.14
GC settings #6 1.087 0.24
GC settings #7 1.03 0.14
GC settings #8 0.95 0.31
14

15. Case study:
Uber
Uber Saved 70K Cores
Across 30 Mission-Critical
Services
https://blog.gceasy.io/2022/08/25/automobile-company-optimizes-performance-using-
gceasy/
15

16. 4. GC Algorithm
GC Algorithm JVM argument
Serial GC -XX:+UseSerialGC
Parallel GC -XX:+UseParallelGC
CMS GC -XX:+UseConcMarkSweepGC
G1 GC -XX:+UseG1GC
Shenandoah GC -XX:+UseShenandoahGC
Z GC -XX:+UseZGC
GC Tuning & Troubleshooting Crash course
https://www.youtube.com/watch?v=6G0E4O5yxks
16

17. 17
GC Logging

18. 18
Healthy Application

19. 19
Acute Memory Leak

20. 20
Memory Leak

21. 5. GC Logging
-XX:+PrintGCDetails -XX:+PrintGCDateStamps -Xloggc:<file-path>
Till Java 8
-Xlog:gc*:file=<file-path>
From Java 9
yCrash, GCeasy, HP Jmeter, Garbage cat, IBM GC visualizer
Tools
Overhead added by Garbage Collection Logging
Almost Zero overhead
21

22. -Dsun.net.client.defaultConnectTimeout,
-Dsun.net.client.defaultReadTimeout
22
Network Timeout settings

23. Application Architecture
JDBC
SOAP
MainFrame
REST
Server Thread Pool
Application Server
HTTP(S) request
23

24. Application Architecture
JDBC
SOAP
REST
Server Thread Pool
Application Server
HTTP(S) request
24
MainFrame

25. -Dsun.net.client.defaultConnectTimeout,
-Dsun.net.client.defaultReadTimeout
6.
-Dsun.net.client.defaultConnectTimeout=2000
-Dsun.net.client.defaultReadTimeout=2000
sun.net.client.defaultConnectTimeout specifies the timeout (in milliseconds)
to establish the connection to the host. For example, for HTTP connections, it
is the timeout when establishing the connection to the HTTP server.
sun.net.client.defaultReadTimeout specifies the timeout (in milliseconds)
when reading from the input stream when a connection is established to a
resource
25

26. 26
-XX:+HeapDumpOnOutOfMemoryError,
-XX:HeapDumpPath
Facilitates to debug OutOfMemoryErrors

27. -XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath
7.
-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath={heap-dump-file-path}
Learn more OutOfMemoryError related JVM arguments
Tools
HeapHero, yCrash, Eclipse MAT
27

28. 28
Ram Lakshmanan ram@tier1app.com
@tier1app
This deck will be published in:
https://blog.ycrash.io
Learn to troubleshoot like a pro with my online training program
https://www.linkedin.com/company/ycrash