CPU usage with 8.3

[JSA]

Just yesterday I upgraded my NI-DAQ software to version 8.3 (on my PC I had been using 7.4).  The CPU usage of my app went from 0-10% to 40-60%.  We got a report from a customer in the field who upgraded to 8.3, and (on a slower CPU) they are seeing their CPU usage pegged at 100%.  This is disturbing.  I am aware that versions 7.0-7.3 had issues with CPU usage that were fixed in version 7.4.  I haven't done extensive testing yet to check if this really degrades the "feel" of my application, but I'm worried about performance on slightly slower CPU's which previously worked fine.  NI-DAQ driver installation is such a hassle (I mean, really, 550+ MB for a driver update?) that I hate to recommend people downgrade to 7.5 when their cards come with 8.3.

The app is written in C++ using the C API, and is continuously sampling data at 50k/s.  Thanks for any info.

[Jonathan_Brumley]

Hi JSA,

I would like to try to reproduce your issue.  What device are you using with DAQmx and how fast is your CPU/computer?

-- Jonathan

[JSA]

I just got more info from the customer, and apparently something went wrong with the version 8.3 installation and it turns out they were using some older version of the NI-DAQ software (I do not know what version)... our software automatically drops down to using Traditional NI-DAQ if NI-DAQmx doesn't load.  So the 100% CPU usage is suspect, because they may be using one of the versions that has that issue.  This was on an old E series card, but isn't worth worrying about until they can get 8.3 installed (probably by uninstalling all NI stuff first).

However, I did see the 40-60% usage on a 2.4GHz Pentium IV (non HT) CPU using the PCI-6251 card.  On version 7.5 of the drivers with the same PC and the same software the CPU usage hovers around 0-10%.  It's probably not a show stopper, everything still runs with enough headroom on our newer PC's, but it worries me when it comes to older PC's that we have out in the field if they want to upgrade.  The PC is doing 8 channels of data acquisition at 50k/s each.

Thanks for the help.

[Jonathan_Brumley]

Hi again,

No update yet.  We did a quick review of the changes since DAQmx 7.4 and we don't immediately see a change that would affect CPU utilization. 

I would like to make sure I am reproducing your application as best as possible.   Can you provide a small code snippet showing the DAQmx calls and parameters you are using to setup your acquisition and read back the data? 

Also, did you upgrade any other software (such as CVI) when you upgraded DAQmx?

[Artem ViTec]

see my message on
http://forums.ni.com/ni/board/message?board.id=170&message.id=223599