LV and multi-core, acquire data with DAQmx on dual-core

[MicheleS]

Hi all,

The affinity is set for the two CPU; if I run CPU Test.vi the CPU usage is 50% (20% of the first, 80% of the second).

For the acquisition I used timed loop; is it better put some delay or "offset/phase"? I've tried to put in one loop 5ms of offset but nothing change.
There aren't produce/consumer pattern but only the default buffer of the DAQmx; I wait for the data in "sleep mode" (1 sec).
I attach an image of the task manager: ACQ in "PAUSE" is when I got the problem and I don't received data; after, when the acquisition "restart", the "available samples" increase a lot.

I don't use USB device but two PXI card with fiber connection to the PC (8336)

[jjcimon]

I am not sure it is cause by the usb driver
the cause is may be the cpu having on other priority
and not listening,


Could you check in the task manager,

[jjcimon]

I was not finishes,
check the task manager on the processus tab and
sorted by process (greater first)
when the cpu load at 100% occurs, look to see
the process that consume cpu time
and get the result back

Jacques

[MicheleS]

Hi Jacques,

in the process list I see that Labview is the process that use much CPU, 50% of the total (100% on one core, 0% on the other)

thanks

[shoneill]

I don't know if you're investigated the possibility of USB problems, but a sudden "loss" of a USB device can also cause a program to block one core of a dual-core processor (retrying the communications).

Shane.

[MicheleS]

Hi,
finally I have try to use LV 8.2.1 to compile my application.

Probably there was a problem of synchronization and thread-switch between timed loops.

Now it works fine also with dual-core PC.

Thanks a lot for all helps.

[JordanRandall]

Hey Michele,

Thanks for the follow up! I'm glad everything is working for you. Now with the release of LabVIEW 8.5, I would encourage you to give it a test run as well!

Happy Programming!

[MicheleS]

Hi Jordo,
I'm waiting for the delivery of the 8.5 to test my appl.
I've seen that there's support for multi-core processor.

Thanx

[billings11]

I have a similar problem with dual core Athlong 64 4200 machines on ASUS AV8 mainboards.  I have PCI-6251's to acquire data.  There is definitely a timing problem in DAQmx when used with fast dual core mahcines.  This is simply continuous simultaneous acquisition and generation on ao0 and ai0. 

The 6251 is plugged into a CB-68 with nothing connected.  Normally I should just be picking up white noise and some coupling from the ao, but every so often I get those huge noise spikes.  They aren't there if I run the same code on a single core machine.  Also if I go in the BIOS and set the CPU speed to 1500MHz instead of 2100MHz the problem goes away.  The spikes are smaller if I connect the acquisition channel to a lower source impedance, but they are still there on the order of several millivolts even if I short the ai to ground.