Startup Time Comparison - OpenJ9 vs. HotSpot

JVM Tutorials - Herong's Tutorial Examples

∟Startup Time Comparison - OpenJ9 vs. HotSpot

This section provides a tutorial example on how to compare startup time of OpenJ9 and HotSpot JVMs. My tests show that OpenJ9 total execution time is much slower than HotSpot on a CentOS Linux computer.

OpenJ9 document also claims that OpenJ9 JVM startup time is 66% faster than HotSpot. Here is what I did to verify this on my CentOS computer.

1. Verify OpenJDK/HotSpot installation:

[herong$ java -version
openjdk version "11.0.7" 2020-04-14 LTS
OpenJDK Runtime Environment 18.9 (build 11.0.7+10-LTS)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.7+10-LTS, mixed mode, sharing)

2. Verify OpenJDK/OpenJ9 installation:

herong$ ./jdk-14.0.1+7-jre/bin/java -version
openjdk version "14.0.1" 2020-04-14
OpenJDK Runtime Environment AdoptOpenJDK (build 14.0.1+7)
Eclipse OpenJ9 VM AdoptOpenJDK (build openj9-0.20.0, JRE 14 Linux ...
OpenJ9   - 05fa2d361
OMR      - d4365f371
JCL      - 5757187cae based on jdk-14.0.1+7)

3. Use a simple Java program, Hello.java, to test startup.

class Hello {
   public static void main(String[] a) {
      System.out.println("Hello world!");
   }
}

4. Run Hello.java with OpenJDK/HotSpot, and measure the total execution time, which includes startup time with a shell script

herong$ more run-HotSpot
javac Hello.java
time java Hello

herong$ ./run-HotSpot
Hello world!

real  0m0.029s
user  0m0.038s
sys   0m0.008s

5. Run Hello.java with OpenJDK/OpenJ9, and measure the total execution time, which includes startup time with a shell script

herong$ more run-OpenJ9
./jdk-14.0.1+7-jre/bin/javac Hello.java
time ./jdk-14.0.1+7-jre/bin/java Hello

herong$ ./run-OpenJ9
Hello world!

real  0m0.090s
user  0m0.071s
sys   0m0.045s

6. Run Hello.java with OpenJDK/OpenJ9 with -Xquickstart, and measure the total execution time, which includes startup time with a shell script

herong$ more run-OpenJ9-quick
./jdk-14.0.1+7-jre/bin/javac Hello.java
time ./jdk-14.0.1+7-jre/bin/java -Xquickstart Hello

herong$ ./run-OpenJ9-quick
Hello world!

real  0m0.083s
user  0m0.059s
sys   0m0.046s

6. Compare test results:

                           Real     User      Sys
                           Time     Time     Time
                       -------   ------   ------
HotSpot                 0.029s   0.038s   0.008s
OpenJ9                  0.090s   0.071s   0.045s
% Slower                  201%      87%     463%

HotSpot                 0.029s   0.038s   0.008s
OpenJ9 w/ quickstart    0.083s   0.059s   0.046s
% Slower                  186%      55%     475%

My test shows that OpenJDK/OpenJ9 is much slower than OpenJDK/HotSpot. But mu measurements are total execution times that include JVM startup time, my program execution time, and JVM shutdown time. I can not conclude that OpenJDK/OpenJ9 startup time is slower than OpenJDK/HotSpot.