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haydent
Journeyman III

Bug- 100% CPU usage when >1 GPU installed & used

normally: 1 gpu installed & used = 1% cpu usage

This is very commonly talked about so its not just me and you likely already know about it.

during opencl activity (btc mining) when i had 1 card installed (6950) i would get 1% cpu usage, but now i have 2 installed i get 100% cpu usage on the core i set their affinity to.

i had the same problem with various driver and sdk versions not being able to fix it.

it creates alot of extra heat and power usage for apparently no good reason as the cpu shouldnt be used at all....

we really appreciate the flash video lockup fix in 11.7, that was very annoying.

a fix to this also would be the last widespread problem ive heard of...

 

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60 Replies
haydent
Journeyman III

Bug- 100% CPU usage when >1 GPU installed & used

here are a selection of threads discussing the issue:

http://forum.bitcoin.org/?topic=6188.0

http://forum.bitcoin.org/index.php?topic=6948.0

http://forum.bitcoin.org/?topic=4446.0

http://forum.bitcoin.org/index.php?topic=5954.0

http://forum.bitcoin.org/index.php?topic=26605.0

http://forum.bitcoin.org/index.php?topic=7991.0

http://forum.bitcoin.org/index.php?topic=27322.0

http://forum.bitcoin.org/index.php?topic=17767.0

http://forum.bitcoin.org/index.php?topic=18719.0

http://forum.bitcoin.org/index.php?topic=24786.0

http://forum.bitcoin.org/index.php?topic=19951.0

http://forum.bitcoin.org/index.php?topic=30818.new#new

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simonk83
Journeyman III

Bug- 100% CPU usage when >1 GPU installed & used

Signed up to add my support for this.  Very annoying bug that we were all hoping would be fixed with 11.7.  Unfortunately not (and neither in 11.8, so far at least).

If this could be looked at that would be great.


Thanks.

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dishwara
Journeyman III

Bug- 100% CPU usage when >1 GPU installed & used

I too faced this problem. The programs are written in OpenCL to use ONLY GPU's. But besides GPU's the programs also uses some CPU. The CPU usage varies from 10% to even some times 100%. This is really annoying as CPU getting used, it doesn't allow other programs, background programs to work properly. Besides why should a program written in OpenCL to use ONLY GPU use CPU also?

OpenCL development team took this matter serious & give some solution to reduce CPU usage to 0

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rorirub
Journeyman III

Bug- 100% CPU usage when >1 GPU installed & used

I can confirm that with a 6950 on win7 x64, using Catalyst 11.7 or 11.8 preview, I get 100% cpu usage on any OpenCL app. Not just bitcoin, but OCLHashCat and ighashgpu as well.

When using 11.6, the cpu usage is as minimal as it needs to be. But, 11.6 still has the UVD crash bug.

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quadboon
Journeyman III

Bug- 100% CPU usage when >1 GPU installed & used

i can also confirm this bug. i tried with oclHashcat-lite and the SDK example programs on ubuntu linux, 64 bit. with catalyst 11.6 i had 0% cpu load while with catalyst 11.7 i have 100% cpu load.

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MicahVillmow
Staff
Staff

Bug- 100% CPU usage when >1 GPU installed & used

Thanks for reporting this, this is a known issue with multi-gpu configurations and we are working on a solution.
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quadboon
Journeyman III

Bug- 100% CPU usage when >1 GPU installed & used

sorry, but let me correct this. it is not a multi-gpu problem. it is a general problem.

and the base of the problem is the gpu synchronization. for example, the command clFinish() which is used for wait till all commands in the queue are finished is told to be blocking and thereby creating 0% cpu.

and this worked fine on linux till cat 11.7. means with 11.6 and older it works and with 11.7 the behavior is more like now its doing a cpu burning loop to wait for the commands finish.

on windows its diffrent. the cat 11.7 behavior was seen since some time. with cat 11.6 it already was present and i guess some older versions, too. but i remember some time in 2010 (cat 10.x) where it worked good.

if you want to reproduce (this works on a single gpu as well):

on linux: install cat 11.6 and SDK 2.4, download oclHashcat-lite, run the example script and watch cpu activity -> 0%

now switch to cat 11.7. cpu activity -> 100%

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haydent
Journeyman III

Bug- 100% CPU usage when >1 GPU installed & used

Originally posted by: MicahVillmow Thanks for reporting this, this is a known issue with multi-gpu configurations and we are working on a solution.


 

this is very good to hear, thankyou for the news. 🙂

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rorirub
Journeyman III

Bug- 100% CPU usage when >1 GPU installed & used

Originally posted by: MicahVillmow Thanks for reporting this, this is a known issue with multi-gpu configurations and we are working on a solution.


By that, do you mean that it's a bug in multi-gpu configuration that affect single gpu configuration? Because I get the bug with a single gpu.

When can we expect this problem fixed? Is it a far cry for it to be fixed in the final 11.8 (the UVD fix came a month earlier than estimated)?

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