直接内存是咋分配的

UnpooledDirectByteBuf

protected UnpooledDirectByteBuf(ByteBufAllocator alloc, int initialCapacity, int maxCapacity) {
    super(maxCapacity);
    if (alloc == null) {
        throw new NullPointerException("alloc");
    }
    if (initialCapacity < 0) {
        throw new IllegalArgumentException("initialCapacity: " + initialCapacity);
    }
    if (maxCapacity < 0) {
        throw new IllegalArgumentException("maxCapacity: " + maxCapacity);
    }
    if (initialCapacity > maxCapacity) {
        throw new IllegalArgumentException(String.format(
                "initialCapacity(%d) > maxCapacity(%d)", initialCapacity, maxCapacity));
    }

    this.alloc = alloc;
    setByteBuffer(ByteBuffer.allocateDirect(initialCapacity));
}

public static ByteBuffer allocateDirect(int capacity) {
    return new DirectByteBuffer(capacity);
}

就是这么暴力，直接内存就是new出来的