FULL PRODUCT VERSION :
java version "1.8.0_91"
Java(TM) SE Runtime Environment (build 1.8.0_91-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.91-b14, mixed mode)
ADDITIONAL OS VERSION INFORMATION :
SunOS tc-perf-026 5.11 11.2 i86pc i386 i86pc
A DESCRIPTION OF THE PROBLEM :
When I start the jvm with the following flags:
-XX:MaxDirectMemorySize=100g -Xmx2048m
I should be able to call java.nio.ByteBuffer.allocateDirect(32 * 1024 * 1024) 512 times to allocate a total of 8GB - but I get an OutOfMemoryError a bit before 2GB have been allocated.
This works fine on OS X, Windows and Linux but not on Solaris. But If I do start the solaris JVM with the following flags:
-XX:MaxDirectMemorySize=100g -Xmx2049m
then I'm able to allocate the 8GB of direct byte buffers.
STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
I've included a simple test class (Buffers.java) that reproduces the problem. You just have to make sure:
- that you're running it on a machine with enough free ram
- that you add -XX:MaxDirectMemorySize=100g and -Xmx2g on the command line
EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The above Buffers class should report that it successfully allocated the 8GB.
ACTUAL -
The above Buffers class catches OutOfMemoryError when a little below 2GB have been allocated.
REPRODUCIBILITY :
This bug can be reproduced always.
---------- BEGIN SOURCE ----------
import java.nio.*;
import java.util.*;
public class Buffers {
// 32MB * 256 == 8GB
private static final int BUFFER_SIZE = 32 * 1024 * 1024;
private static final int BUFFER_COUNT = 256;
public static void main(String[] args) throws Exception {
long counter = 0L;
try {
List<ByteBuffer> buffers = new ArrayList<ByteBuffer>();
for (int i=0 ; i<BUFFER_COUNT ; i++) {
ByteBuffer b = ByteBuffer.allocateDirect(BUFFER_SIZE);
buffers.add(b);
counter += BUFFER_SIZE;
}
} catch(Throwable t) {
t.printStackTrace();
}
System.out.println("allocated : " + (counter / 1024 / 1024 + " MB"));
}
}
---------- END SOURCE ----------
CUSTOMER SUBMITTED WORKAROUND :
I found two:
1) tell the JVM that its max heap size is over 2GB (ie: -Xmx2049m)
2) use libumem's mmap backend to start the JVM:
LD_PRELOAD=libumem.so UMEM_OPTIONS=backend=mmap java ...