[nmglug] odd IO-Wait conditions

Andrew Farnsworth farnsaw at stonedoor.com
Mon Jan 24 12:31:39 PST 2011


You are probably monopolizing the processing power of the graphics card
while the code is running.  When you step through the code, it runs only one
cycle (not cpu cycle, one computation) and then leaves the GPU alone while
waiting for you to click "next step".

Andy

On Mon, Jan 24, 2011 at 3:16 PM, Aaron Birenboim <aaron at boim.com> wrote:

> I am working on a scientific computing problem (using the GPU -- OpenGL)
> where when I try to do my test runs, I get into a state where any
> graphics response of my computer comes nearly to a halt,
> the machine becomes sluggish, and it spends most of it's time
> reporting a "wait" state.
>
> I cannot reproduce this behavior while stepping through in
> a debugger.  It only happens several seconds into
> a longer full-speed run.
>
> This test routine is dumping many tens (perhaps hundreds)
> of MB of disk writes per second.  Scores of files,
> each of size 1 to 8 MB.
>
> How can I find out what is causing this near lock-up?
> How can I avoid it?
>
> Is this kind of thing often seen with many mid
> sized files being generated?
> Could it be ab OpenGL thing, where something is not
> cleanly flushed, and the GPU is doing something odd?
>
> (I am writing to floating point FBO's, and retrieving
>   results with glReadPixels())
>
> Thanks for any advice:
>
>          aaron
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