Latency about 7000 with Latency-Test, raises to above 100.000 with latency-plot

17 Jan 2017 14:03 #85918 by DomCa
Hi all!

I used the LinuxCNC download and installed from a USB stick. I just set up a PC (old dual core Athlon). I got it down to latencies about 7000 or lower for both threads. I deactivated everything in the bios and shifted the IRQs to the core 0.

I run 4 glxgears, buck bunny in 1080 30fps and browse on the internet.

The latencies stay low if I use the latency test. But they immediatly go up if I use the latency-plot.

Any idea?

17 Jan 2017 14:32 #85923 by PCW
No idea why you get such different results, but you might try latency-histogram as an additional data point
18 Jan 2017 06:26 #86034 by DomCa

Thanks for the tip. I tried it and get the same result. I can run for 2-3 hours with the latency-test showing under 7000 and when I start the latency-plot or - histogram after some seconds there are some realy high values 20.000 up to 100.000 or even more. Not permanently but spikes...

Which values can I trust? I hoped the PC would be good for LinuxCNC.

02 Mar 2017 18:55 #88895 by Bari
I just compared -test to -plot and -histogram and I got the highest latency test results using -test. This was tested on only one board/cpu using the latest kernel in LCNC 2.7.8 for only about 12 hours for each test.
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