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OpenCL

tgreen
Journeyman III

Kernel on AMD "dies" after being idle 100ms

I am doing the following test

0 : compile kernel for GPU

1 : start timing

2 : Launch kernel solving a problem returning a result

3 : stop timing

4 : Sleep(100ms)

5 : show timing

6 : goto 1

I have experienced that using a NVidia card the time measured is in my case always 25ms with or without the sleep in line 4.

Using an AMD card I see the time as 32ms when sleeping and 16 ms when not sleeping.

If I change the sleep to some value less than 100ms, then it does not affect the gpu kernel time.

For both NVidia and AMD I see the first launch as taking longer and for both the following  times are lower.

Is there a well described flushing/pausing/something of the kernel on AMD devices which I should know about?

Amd timing with Sleep inbetween calls

GPU:55

GPU:35

GPU:35

GPU:35

GPU:35

GPU:32

GPU:32

GPU:32

GPU:32

GPU:32

Amd timing without sleep between calls

GPU:49

GPU:16

GPU:15

GPU:15

GPU:16

GPU:16

GPU:16

GPU:16

GPU:15

GPU:16

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himanshu_gautam
Grandmaster

Re: Kernel on AMD "dies" after being idle 100ms

Hi Thomas,

Nice problem. Lets get to the bottom of it.

But just to remind everyone, a thread can be solved by many people, so better give full details on every new thread.

CPU, GPU(s), Driver Versions, SDK Version, OS , Bitness (32 or 64).

It will also help to resolve the issue quickly if you can attach a zip file, for easy reproduction. If required use the kernel launch testcase i attached in your previous thread, or use other SDK Samples.

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