并发内核执行和OpenCL设备分区

Question

Recently I needed to do some experiments which need run multiple different kernel on AMD hardware. But I have several questions before starting to coding hence I really need your help.

First, I am not quite sure whether AMD HW can support concurrent kernel execution on one device. Because when I refer to the OpenCL specs, they said the command queue can be created as in-order and out-of-order. But I don't "out-of-order" mean "concurrent execution". Is there anyone know info about this? My hardware is AMD APU A8 3870k. If this processor does not support, any other AMD products support?

Second, I know there is an extension "device fission" which can be used to partition one device into two devices. This works only on CPU now. But in OpenCL specs, I saw something, ie "clcreatesubdevice", which is also used to partition one device into two? So my question is is there any difference between these two techniques? My understanding is: device fission can only be used on CPU, clcreatesubdevice can be used on both the CPU and the GPU. Is that correct?

Thanks for any kind reply!

Answer 1

Real concurrent kernels is not a needed feature and causes so much troubles to driver developers. As far as I know, AMD does not support this feature without the subdevice split. As you mentioned, "out-of-order" is not cuncurrent, is just a out of order execution of the queue.

But what is the point in running both of them in parallel at half the speed instead of sequentially at full speed? You will probably loose overall performance if you do it in such a way.

I recomend you to use more GPU devices (or GPU + CPU) if you run out of resources in one of the GPUs. Optimizing could be a good option too. But splitting is never a good option for real scenario, only for academic purposes or testing.