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Infering the GPU Active cycles in Mali T-628

maasa

Hi ,

I have the following questions regarding Mali T-628 GPU.

 I am running a 3D convolution OpenCL kernel in Mali T-628 GPU (set of 4 cores device).  I obtain the GPU cycles counter using Streamline

The GPU Vertex-Tiling-Compute:Activity counter shows 100% utilization . So this translates to 100% GPU utilization.

Then the GPU active cycles should match the runtime right?

In a sampling interval of 1s , the GPU active cycles should be 600*10^6 whereas the GPU active cycles reported by streamline is 3141810

Why this discrepancy?

Please help me understand this.

Thanks

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  • +1 Arm Employee Badge in reply to maasa

    Hi massa, 

    I'm not sure I can give you a better answer. 

    The "Activity" counter is a software metric reported by the kernel driver; i.e. how busy does the driver think the hardware is.

    The other counters are hardware counters reported by the GPU while work is running; i.e. how busy does the hardware think it is.

    The only conclusion I can draw is that your platform BSP is down-clocking the GPU to ~300Mhz for some reason. The frequency management is outside of the Mali driver / hardware and is provided by the chipset manufacturer, so I can't explain why it's decided to do this.

    HTH, 
    Pete

Reply
  • +1 Arm Employee Badge in reply to maasa

    Hi massa, 

    I'm not sure I can give you a better answer. 

    The "Activity" counter is a software metric reported by the kernel driver; i.e. how busy does the driver think the hardware is.

    The other counters are hardware counters reported by the GPU while work is running; i.e. how busy does the hardware think it is.

    The only conclusion I can draw is that your platform BSP is down-clocking the GPU to ~300Mhz for some reason. The frequency management is outside of the Mali driver / hardware and is provided by the chipset manufacturer, so I can't explain why it's decided to do this.

    HTH, 
    Pete

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