well this was interesting. Looks like these unusual delay is happening only with your APU. I have seen numbers better than nvidia's at my end, for discrete GPUs.
Also I checked http://www.fit-pc.com/web/fit-pc/fit-pc3-info/#Specifications, and it looks something in the lines of raspberry pi processors. I am not sure, if i will be able to arrange it here. Anyways will try.
You can probably check with the fit-pc, in case they can help. Another suggestion can be to try the performance with a older driver (probably 12.10). Note these are just guesses.
Thank you again for your assistance. I would expect numbers better than my nvidia results as my nvidia card is about the worst card nvidia makes that supports OpenCL. I tried several previous drivers including 12.10 and there was no difference at all in the delay. I have asked fit-pc to see if they can help.
I am interested to find out if this is a problem with some AMD APUs in general or if it is something specific about the fit-pc hardware that is causing it.
Just to confirm that APU A6-4455M with HD 7500G GPU integrated observed the same phenomenon.
The delay between submit->start is extremely high, even longer than the kernel execution time itself under Kubuntu 12.10.
However, I have a windows port of my OpenCL kernel, I also test it under windows, and find that this large delay is greatly mitigated under windows 7.
Inserted Image is the codeXL snapshot under windows.
The submit->start delay for my kernel(green part) is almost 2 ms, which is also a lot. While the equivalence delay under kubuntu can increase to 7 ms.
Another thing confused me is that the same kernel has around 2 times performance difference between kubuntu and windows7. the kernel execution time in the figure is 10 ms
while the one under kubuntu is only 6ms.
I check the frequency of my GPU running under kubuntu and windows 7, both of them will boost to 423MHz. The driver of these two systems differ so much?
I will try to connect to some people. But IMHO such complaints should actually reach AMD from the manufacturer (fit-pc). Anyways, will let you know if i hear something useful. Thanks