Youtube slows down GPU clock

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Youtube slows down GPU clock

Postby Bobcat » Sat Dec 11, 2010 2:47 pm

I was switching between Youtube videos while running the GPU client and got a NaN error. This got me to investigate what was going on, and to make a long story short:

I have a Sapphire 5670. It has three clock rates (aka Performance States):
    GPU 157 MHz / Mem 300 MHz / VDDC 0.9 V
    GPU 400 MHz / Mem 900 MHz / VDDC 1.0 V
    GPU 775 MHz / Mem 1000 MHz / VDDC 1.1 V

It idles at 157 MHz. When running the folding GPU client, the 775 MHz setting is used automatically. But if I start up a Youtube video, it switches to the 400 MHz setting, even when folding. To make matters worse, I believe the clock switch interrupts the GPU processing and may have caused the NaN error.

The solution is to disable hardware acceleration (start a Youtube video, go into the Flash settings, and disable hardware acceleration). This results in the card using the 775 MHz clock when folding, even when watching Youtube videos. It also avoids the hiccup that occurs when switching clock rates.
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Re: Youtube slows down GPU clock

Postby codysluder » Sat Dec 11, 2010 4:44 pm

Welcome to the FAH help forum Bobcat.

Thanks for the tip. I've seen a similar suggestion regarding disabling or reducing hardware acceleration for Windows although nobody reported NaN errors. I never knew that you could disable Flash acceleration.

Bobcat wrote:The solution is to disable hardware acceleration (start a Youtube video, go into the Flash settings, and disable hardware acceleration).
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Re: Youtube slows down GPU clock

Postby Bobcat » Sat Dec 11, 2010 6:59 pm

I don't know the cause of the NaN error, but Occam's Razor would suggest the cause was related to Youtube and/or the clock rate switching. I'm not overclocked and the GPU temperature was only 55 C. I was reassigned the same WU and completed it without errors.

Hardware acceleration is something relatively new for Flash. It sounds like something that would have been useful at least 10 years ago, but CPUs are so fast now, I don't see why it's needed. The real problem isn't the hardware acceleration itself, but that it requires the GPU clock to slow down. It's too bad they don't run it at full clock speed.
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Re: Youtube slows down GPU clock

Postby codysluder » Sat Dec 11, 2010 7:39 pm

Changes in clock-rates have been known to disrupt FAH. If a GPU is being used for graphics and the clock-rate change causes errors, the screen will soon refresh with the correct data and nobody will care. FAH will continue on using the incorrect data until one of the error-checking routines catches the error.
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Re: Youtube slows down GPU clock

Postby Bobcat » Sat Dec 11, 2010 8:08 pm

What's the current state of Fast User Switching on Win7 with the systray 6.32 client and core 11 on an ATI card? Does that work, or do I have to pause the client when switching users?
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Re: Youtube slows down GPU clock

Postby bruce » Sat Dec 11, 2010 8:23 pm

Last I heard, GPU processing cannot handle switching users or connecting with Microsoft's Remote Desktop or processing as a service. Anything that disturbs the connection between the FahCore and the GPU is going to create errors and will probably abort the current WU.
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Re: Youtube slows down GPU clock

Postby mhouston » Sat Dec 11, 2010 10:35 pm

Driver initiated switching, like running HW accelerated video, shouldn't be causing errors. Obviously something is going on so we could have a race somewhere in the old Brook code or the driver handoff between CAL and the multimedia driver is causing a hiccup. Hopefully the CL version will smooth things out since one of the common usage cases of OpenCL is to decode video using the HW video engine while processing the frames in OpenCL.
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Re: Youtube slows down GPU clock

Postby Ivoshiee » Sat Dec 11, 2010 11:49 pm

mhouston wrote:Driver initiated switching, like running HW accelerated video, shouldn't be causing errors. Obviously something is going on so we could have a race somewhere in the old Brook code or the driver handoff between CAL and the multimedia driver is causing a hiccup. Hopefully the CL version will smooth things out since one of the common usage cases of OpenCL is to decode video using the HW video engine while processing the frames in OpenCL.

Good to know, but when will the OpenCL core be among us?
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Re: Youtube slows down GPU clock

Postby mhouston » Sun Dec 12, 2010 12:15 am

That is up to the folks at Stanford.
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Re: Youtube slows down GPU clock

Postby P5-133XL » Sun Dec 12, 2010 7:36 am

Mr. Houston,

Just a simple question and I will understand if you choose not to answer but is anyone (Nvidia or ATI/AMD working on a priority system for GPU's? Once they start being shared by applications rather than being dedicated just to video, it seems to me that there will invariably be a conflict between different applications striving for their attention/resources.
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Re: Youtube slows down GPU clock

Postby Bobcat » Tue Dec 14, 2010 1:57 am

I just found another Flash application that forces the GPU clock to 400 MHz, even though 'hardware acceleration' is turned off. Oh well. At least the Youtube problem can be avoided. When I use these other flash applications, I'll just pause the GPU client first.
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Re: Youtube slows down GPU clock

Postby mhouston » Tue Dec 14, 2010 5:42 am

P5-133XL wrote:Mr. Houston,

Just a simple question and I will understand if you choose not to answer but is anyone (Nvidia or ATI/AMD working on a priority system for GPU's? Once they start being shared by applications rather than being dedicated just to video, it seems to me that there will invariably be a conflict between different applications striving for their attention/resources.


The main issue is that GPUs are an asynchronous offload and most OSs don't understand the GPU as a compute resource to be managed, so massive batches of work can be sent to the GPU all at once without the OS understanding it. There are actually software ways to make the GPU play a little nicer and more closely follow the priority of the main process (the CPU side of the process), but they can also increase the overhead of dispatching to the GPU. It's a balancing act that is being researched. The Brook+ based client attempted to implement a backoff mechanism with mixed success in that it could backoff of the GPU some of the time and ramp back up when the GPU was available, but it would burn a CPU core much of the time and/or had stability problems. I'd like to take another pass at trying some tricks in the OpenCL client once testing is complete.
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Re: Youtube slows down GPU clock

Postby P5-133XL » Tue Dec 14, 2010 8:04 am

Thanks for addressing my question.
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Re: Youtube slows down GPU clock

Postby Bobcat » Fri Dec 17, 2010 11:58 am

bruce wrote:Last I heard, GPU processing cannot handle switching users or connecting with Microsoft's Remote Desktop or processing as a service. Anything that disturbs the connection between the FahCore and the GPU is going to create errors and will probably abort the current WU.

Looks like Fast User Switching is OK. From http://folding.stanford.edu/English/FAQ-ATI2 -

A major upside to using CAL and CUDA is that DirectX context switches no longer affect the client. Actions such as fast-user switching, or locking your computer have no effect on GPU processing. Remote desktop does still affect the GPU client and will cause the FahCore to fail when a connection is initiated; VNC does not have the same problem and can be used as an alternative (this needs to be tested on NVIDIA hardware).
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Re: Youtube slows down GPU clock

Postby bruce » Fri Dec 17, 2010 1:31 pm

Bobcat wrote:
bruce wrote:Last I heard, GPU processing cannot handle switching users or connecting with Microsoft's Remote Desktop or processing as a service. Anything that disturbs the connection between the FahCore and the GPU is going to create errors and will probably abort the current WU.

Looks like Fast User Switching is OK. From http://folding.stanford.edu/English/FAQ-ATI2 -

A major upside to using CAL and CUDA is that DirectX context switches no longer affect the client. Actions such as fast-user switching, or locking your computer have no effect on GPU processing. Remote desktop does still affect the GPU client and will cause the FahCore to fail when a connection is initiated; VNC does not have the same problem and can be used as an alternative (this needs to be tested on NVIDIA hardware).


This seems to be a battle between Microsoft and NVidia/ATi. At the time the FAQ was written, that was true. Microsoft had designed DirectX and was happy with the design. NVidia/ATi did not design CUDA/CAL the same way. SInce then, Microsoft has been making changes to Win7 and apparently have decided that there's a security risk so they've changed the rules for CUDA/CAL. We can update the FAQ, but I'm not sure what the final word is going to be.
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