openjdk 11.0.14.1 2022-02-08
Consider the following simple Java program.
public static void main( String[] args ){
int i[] = new int[Integer.MAX_VALUE / 2];
}
Here int is 4 byte in size so allocating int[Integer.MAX_VALUE / 2] requires 4G of free heap size. Now let's run the program with different options.
I. -XX:+UseParallelGC -Xmx5g
Result: Crash with OutOfMemoryError.
Even in spite of the fact that heap size is large enough. It's clear since the -XX:NewSize is 1310 MB by default and the Old generation is not large enough.
II. -XX:+UseParallelGC -Xmx5g -XX:MaxNewSize=128m -XX:NewSize=128m
Result: Completed normally
The application runs fine since the Old generation is large enough to hold the array allocation.
Now let's change the collector from Parallel to G1
III. -XX:+UseG1GC -Xmx5g -XX:MaxNewSize=128m -XX:NewSize=128m
Result: Crash with OutOfMemoryError.
And this is what I have no idea about. I thought that adjusting -XX:G1HeapWastePercent would help, but it didn't.
Why can't G1 hold the allocation of the array and what options to adjust in order to fix it?
