On Thu, Sep 15, 2016 at 9:35 AM, Joshua Glenn <joshgle...@gmail.com> wrote:

> .....You run it by opening Terminal then copy/paste this command into the
> command line (then press enter):
> while true ; do echo "nothing" > /dev/null ; done
> That will start the cpu hog running, then run the latency test. You should
> see your numbers come down.

I tried it.  I place something a lot like the above command in a script and
run it while testing.  The improvement was dramatic and when I killed the
running script the latency number instantly went way up and back down when
I restarted it.

One refinement I would suggest is placing the command "nice" in front of
your "cpu hog".  This will run it at a lower scheduler priority.  So that
rather then sharing the CPU with your real tasks you need to run it will
run only when those others don't need to use the CPU.  Another works it
will suck up all the "left over" CPU time.

It appears that what is happening is that the CPU will go into a slow-down
states when there is nothing to do but your command ensured there is always
something to be done (stuffing nothing in the bit buckets while using an
interprocess communications pipe" to send the nothing.)   But if you add
the "nice" command in front then it become s "nice cpu hog" that only hogs
the CPU when other software does not need the CPU.    I think THAT can be
run along side LinuxCNC.

All that said I think Gene has sold me on a Mesa FPGA board.  I'll use in
for LunixCNC but also, I've always wanted to learn to program an FPGA.
It's a generally useful skill to have.

I'll get the parallel port too.   Use it on a second development system.


Chris Albertson
Redondo Beach, California
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