presto-main/src/main/java/io/prestosql/execution/buffer/ArbitraryOutputBuffer.java/ArbitraryOutputBuffer/isOverutilized
class ArbitraryOutputBuffer:    @Override
    public boolean isOverutilized()
    {
        return (memoryManager.getUtilization() >= 0.5) || !state.get().canAddPages();
    }