I am using Netty 4.1.17-Final.
I wrote the code to send and receive 100 MB random ASCII. Decoder does not read until ByteBuf becomes 100 MB.
@Override
public void decode(ByteBuffer _in, List<Object> _out) {
if (_in.remaining() == size) { // size = 100 * 1024 * 1024
_in.get(new byte[size]);
}
}
Therefore, Netty buffers 100 MB, but it was not found even by monitoring Direct Memory.
System.out.println(sun.misc.SharedSecrets.getJavaNioAccess().getDirectBufferPool().getMemoryUsed());
ManagementFactory.getPlatformMXBeans(BufferPoolMXBean.class).forEach(buf -> {
System.out.printf("%s: Used=%d, TotalCap=%d%n", buf.getName(), buf.getMemoryUsed(), buf.getTotalCapacity());
});
// Result
// 10
// direct: Used=9, TotalCap=8
// mapped: Used=0, TotalCap=0
Netty used PooledUnsafeDirectByteBuf, but where do you buffer the received data? Or is the direct buffer monitoring method incorrect?
You can tell Netty to not use Unsafe for the direct buffers and so have it show up in JMX again. Unfortunally this also will have some performance impact.
Just use -Dio.netty.maxDirectMemory=0.