How many WUs for a Radeon RX 580 card?

Glenn Hawley, RASC Calgary
Glenn Hawley, R...
Joined: 6 Mar 05
Posts: 27
Credit: 79,046,992
RAC: 572,232
Topic 223319

I just installed a Radeon RX 580 video card with 8Gb VRAM.

I am running two GPU units at a time right now (utilization factor= 0.5), and I see that the VRAM is only about 12% utilized, though the GPU utilization reaches up to 100%.

I have 8 CPUs, thus 16 cores, so the CPU could probably handle more units simultaneously.

So how many work units should that card be able to run at one time? 4? 8? 16???

steffen_moeller
steffen_moeller
Joined: 9 Feb 05
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Credit: 779,978,832
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The two tasks should be fine.

The two tasks should be fine. That is what I went for. I tried three but under my hands at least there was no extra to it.

If you have a bit more space in case and your power-supply scales a bit more then you could add a second card.

Best,

Steffen

archae86
archae86
Joined: 6 Dec 05
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Should be "able" to run may

Should be "able" to run may not be the right question.

Most of us prefer to set the multiplicity for either best overall production or power efficiency, not just the highest number that functions.

Even when there is enough RAM to run an extreme multiplicity, it not only may add little, it may also actually detract.  The GPU does not really run the tasks simultaneously, but switches context.  On modern GPUs the context switch is remarkably efficient, but it is not free.  The main gain in running multiplicity higher than 1X is in giving the GPU useful work to do (on another task) when it must briefly cease work on the current task while it waits for some service from the host CPU.  So as a rule of thumb, if you actually get reported GPU utilization up near 100% consistently (over the full WU time), it is very unlikely there is much to be gained from yet higher multiplicity.

Another issue is that not all WUs have the same requirements.  Currently here at Einstein the Gamma-Ray and Gravity work applications differ greatly in the way they use system resources.  And the immediate previous Gravity Wave batch of work (which ended about a month ago) had hugely varying memory requirements from WU to WU.  Staff has advised that the new batch can vary over more than a 3:1 range.

For your particular 8G GPU, 2X is safe and pretty effective for both the GRP and GW tasks.  You might get some more out of 3X.  You would be singularly unlikely to enjoy the results of running 16X.

Try it.  That is the way to tell.  Just be sure to keep cache request very low (I suggest 0.1 day) so the transitions don't go crazy.

 

Glenn Hawley, RASC Calgary
Glenn Hawley, R...
Joined: 6 Mar 05
Posts: 27
Credit: 79,046,992
RAC: 572,232

The box has only one PCI

The box has only one PCI slot, so I'm limited to one video card.

 

Glenn Hawley, RASC Calgary
Glenn Hawley, R...
Joined: 6 Mar 05
Posts: 27
Credit: 79,046,992
RAC: 572,232

Thanks for the advice. I'll

Thanks for the advice.

I'll run it with 2 WUs for now. 

The computer was putting out about 90,000 credits a day, and at the rate things are going I should end up at nearly 500,000 per day... so I'm going to be quite pleased as things stand. 

My but the box does run warm, though...

archae86
archae86
Joined: 6 Dec 05
Posts: 2,821
Credit: 3,293,970,051
RAC: 2,544,974

Glenn Hawley, RASC Calgary

Glenn Hawley, RASC Calgary wrote:

My but the box does run warm, though...

If you use Account|preferences|project|Resource settings to disallow CPU tasks, once the 174 you have already downloaded finish your box level power consumption will go down appreciably, while your credit rate will go down by much less, so your power efficiency of credit production will go up appreciably.

It is a personal choice--possibly you might prefer it that way.  I do.

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