Java-8 – the java8 metaspacesize flag does not work
I have a simple test code that sets - XX: metaspacesize and - XX: maxmetaspacesize to the same value I don't think Metaspace should be dynamically resized But from my test (checking the Metaspace diagram of visualvm GC and printing the log through jstat), I saw that the Metaspace increased from the low value to the maximum value I set So - XX: does metaspacesize not work properly?
My test code:
try {
while(true){
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(A.class);
enhancer.setUseCache(false);
enhancer.setCallback((MethodInterceptor) (obj,method,args1,methodProxy) -> methodProxy.invokeSuper(obj,args1));
enhancer.create();
Thread.sleep(50);
}
} catch (Throwable throwable) {
throwable.printStackTrace();
}
VM args：
-XX:MetaspaceSize=10m -XX:MaxMetaspaceSize=10m
Java version:
java version "1.8.0_45" Java(TM) SE Runtime Environment (build 1.8.0_45-b14) Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02,mixed mode)
Jstat result: (MC value continues to increase to about 10m)
C:\Users\dyu>jstat -gc 12336 1000 20 S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT GCT 8192.0 8192.0 0.0 2207.8 49152.0 43399.2 131072.0 16.0 7168.0 6777.9 768.0 677.7 1 0.015 0 0.000 0.015 8192.0 8192.0 0.0 2207.8 49152.0 48166.1 131072.0 16.0 7168.0 6777.9 768.0 677.7 1 0.015 0 0.000 0.015 8192.0 8192.0 2592.0 0.0 49152.0 3691.9 131072.0 24.0 8832.0 8403.6 896.0 795.9 2 0.020 0 0.000 0.020 8192.0 8192.0 2592.0 0.0 49152.0 7537.9 131072.0 24.0 8832.0 8403.6 896.0 795.9 2 0.020 0 0.000 0.020 8192.0 8192.0 2592.0 0.0 49152.0 11378.9 131072.0 24.0 8832.0 8403.6 896.0 795.9 2 0.020 0 0.000 0.020 8192.0 8192.0 2592.0 0.0 49152.0 16180.3 131072.0 24.0 8832.0 8403.6 896.0 795.9 2 0.020 0 0.000 0.020 8192.0 8192.0 2592.0 0.0 49152.0 20021.3 131072.0 24.0 8832.0 8403.6 896.0 795.9 2 0.020 0 0.000 0.020 8192.0 8192.0 2592.0 0.0 49152.0 24822.5 131072.0 24.0 8832.0 8403.6 896.0 795.9 2 0.020 0 0.000 0.020 8192.0 8192.0 2592.0 0.0 49152.0 28663.5 131072.0 24.0 8832.0 8403.6 896.0 795.9 2 0.020 0 0.000 0.020 8192.0 8192.0 2592.0 0.0 49152.0 33466.8 131072.0 24.0 8832.0 8403.6 896.0 795.9 2 0.020 0 0.000 0.020 8192.0 8192.0 2592.0 0.0 49152.0 37312.8 131072.0 24.0 8832.0 8403.6 896.0 795.9 2 0.020 0 0.000 0.020 8192.0 8192.0 2592.0 0.0 49152.0 42114.1 131072.0 24.0 8832.0 8403.6 896.0 795.9 2 0.020 0 0.000 0.020 8192.0 8192.0 2592.0 0.0 49152.0 45955.1 131072.0 24.0 8832.0 8403.6 896.0 795.9 2 0.020 0 0.000 0.020 8192.0 8192.0 0.0 3488.0 49152.0 1925.1 131072.0 32.0 10752.0 10225.1 1024.0 934.2 3 0.026 0 0.000 0.026 8192.0 8192.0 0.0 3488.0 49152.0 6737.6 131072.0 32.0 10752.0 10225.1 1024.0 934.2 3 0.026 0 0.000 0.026 8192.0 8192.0 0.0 3488.0 49152.0 11758.5 131072.0 32.0 10752.0 10225.1 1024.0 934.2 3 0.026 0 0.000 0.026 8192.0 8192.0 0.0 3488.0 49152.0 15608.7 131072.0 32.0 10752.0 10225.1 1024.0 934.2 3 0.026 0 0.000 0.026 8192.0 8192.0 0.0 3488.0 49152.0 29056.4 131072.0 32.0 10752.0 10225.1 1024.0 934.2 3 0.026 0 0.000 0.026 8192.0 8192.0 0.0 3488.0 49152.0 34196.6 131072.0 32.0 10752.0 10225.1 1024.0 934.2 3 0.026 0 0.000 0.026 8192.0 8192.0 0.0 3488.0 49152.0 39339.7 131072.0 32.0 10752.0 10225.1 1024.0 934.2 3 0.026 0 0.000 0.026
Solution
You misunderstood the function of - XX: metaspacesize:
The name of this option can be considered misleading unless you interpret it as "expected size", so obviously it should trigger garbage collection when exceeded (while the maximum size defines a hard limit)
There is an open bug report. Jdk-8067205 requires setting the option of initial meta space size