# windows xp 64 causing gpu idling?

**URL:** <https://forums.developer.nvidia.com/t/windows-xp-64-causing-gpu-idling/15179>\
**Category:** CUDA Programming and Performance\
**Created:** [February 26, 2010, 5:29pm UTC](https://forums.developer.nvidia.com/t/windows-xp-64-causing-gpu-idling/15179 "2010-02-26T17:29:11Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![mwd8932](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@mwd8932](https://forums.developer.nvidia.com/u/mwd8932)\
**Post date:** [February 26, 2010, 5:29pm UTC](https://forums.developer.nvidia.com/t/windows-xp-64-causing-gpu-idling/15179/1 "2010-02-26T17:29:11Z")

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I’ve run into a problem that is killing my program execution speed. Mainly, my GPU seems to go idle for approximately 15 to 16 milliseconds after running 500 iterations in a single program. Essentially, prior to 500 iterations, my kernels each run in under 1 ms. After 500, it will run two or three iterations at sub millisecond timeframes then do a single iteration at about 15 to 16 ms.

The timeframe looks like this if its confusing

1st 500 iterations: 0 in terms of milliseconds.  
501st iter: 0  
502nd iter: 0  
503rd: 15  
504th:0  
505th:0  
506th:0  
507th:16

and so on until my program ends. I have confirmed that even calling a kernel with nothing in it also results in the same amount of idle time, albeit far more spread apart. The only thing I can think of that this can be is another process/thread preempting my program while its running on the CPU. Has anyone else run into this problem?

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**Author:** ![mr\_gui](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@mr\_gui](https://forums.developer.nvidia.com/u/mr_gui)\
**Post date:** [April 20, 2010, 3:13pm UTC](https://forums.developer.nvidia.com/t/windows-xp-64-causing-gpu-idling/15179/2 "2010-04-20T15:13:00Z")

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> [@](#):
>
> I’ve run into a problem that is killing my program execution speed. Mainly, my GPU seems to go idle for approximately 15 to 16 milliseconds after running 500 iterations in a single program. Essentially, prior to 500 iterations, my kernels each run in under 1 ms. After 500, it will run two or three iterations at sub millisecond timeframes then do a single iteration at about 15 to 16 ms.
> 
> The timeframe looks like this if its confusing
> 
> 1st 500 iterations: 0 in terms of milliseconds.
> 
> 501st iter: 0
> 
> 502nd iter: 0
> 
> 503rd: 15
> 
> 504th:0
> 
> 505th:0
> 
> 506th:0
> 
> 507th:16
> 
> and so on until my program ends. I have confirmed that even calling a kernel with nothing in it also results in the same amount of idle time, albeit far more spread apart. The only thing I can think of that this can be is another process/thread preempting my program while its running on the CPU. Has anyone else run into this problem?

what is your timing method? cuda or sth. else?

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**Author:** ![Cygnus\_X1](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/cygnus_x1/32/9784_2.png) [@Cygnus\_X1](https://forums.developer.nvidia.com/u/Cygnus_X1)\
**Post date:** [April 30, 2010, 7:41am UTC](https://forums.developer.nvidia.com/t/windows-xp-64-causing-gpu-idling/15179/3 "2010-04-30T07:41:46Z")

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Noticed it too.  
when running my code in cuda profiler I have this “white spots” where - for no reason - GPU is idling, although my host code isn’t doing anything special.

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**Author:** ![Lev](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@Lev](https://forums.developer.nvidia.com/u/Lev)\
**Post date:** [April 30, 2010, 11:56am UTC](https://forums.developer.nvidia.com/t/windows-xp-64-causing-gpu-idling/15179/4 "2010-04-30T11:56:32Z")

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Maybe it is screen display drivver? Try gpu as physX device, use other gpu to display. Also check other os, winxp for example.