Latency questions

Hi all,
I am running Linux CNC compiled from the main git repo using the master branch (current as of today, 29 April 2019). I am running this on a Gentoo Linux kernel 4.19.10-rt8. The computer is a Dell Precision 390 with 6Gb RAM wuth the 82801GR/GH/GHM (ICH7 Family) chipset. I use isolcpus to reduce it to one CPU. I have been using Linux CNC on Gentoo for quite a while so far and it's working well. I have a couple of questions on latency:

1) my latency is about 60,000us which I understand is high. Regardless, I am not seeing this causing any issues when machining. My machine is a homemade 500x600mm 3-Axis made from the Solsylva plans. It runs NEMA23 steppers with lead screws. I run it at about 1800mm/min. The question is: what issues should the high latency be causing? How will it manifest itself as a problem? I suppose the real question is, what benefit will lowering the latency give me?

2) It is usual for the latency to spike after about 5 minutes of the computer running and then settle down? I get 3 60,000us spikes within 5 minutes and then no matter how hard I work the computer it never goes beyond 20,000. Is this common? Does this help me identify the cause of the spikes?

Thanks,
Allistar.

That all is good and well, so no worried there.
Do you get a warning saying latency error while using Linuxcnc ? If not, forget about it, but if you do just edit the inin file and set the base period to something a bit bigger.

If I run LinuxCNC within a few minutes of the computer starting I always get the error. I ignore it and never have any issues with the machining.

What would you expect issues of latency being too high be? Is this about the machine losing steps and therefore not being positioned where the software thinks it is?

That depends on many things, but basically it would be expected to loose some steps. That could range from not noticeable even after a week of heavy use, to missing it's position by a mm after an hour or two of work.
If you home the axis at the start of every new job, you may not notice it ever.
Did you try editing the INI file of your config ? Set it to 100.000 without the dot.

I always rehome the axes when I turn it on. I have run 14 hour programmes before and it X0Y0 is always spot on at the end.

Will setting it to 100000 force LinuxCNC to run slower? That is, can I still get 2000mm/min out of it with the same acceleration? Or will this high base period limit the speed?

no problem to set it that high on your numbers
you shoudt see 3600mm/min at latency 200000
we are talking on nanoseconds
so it is enoph time for you to get a clear step signal
you can also increase the numbers of LETS say Parport reset or the signal length
to a good always stable working mashine
if you see no steploss over hoourers of movement it is perfect
if you like you can go faster and test out the edges of the mashine