Stephen Wille Padnos wrote: > > If you have a chance to try out a core2duo sometime soon, then try > starting up a do-nothing CPU hog. I've found that to help latencies by > roughly an order of magnitude. It's so much better that I actually have > an embedded application (which starts up at boot time) that does a > loadusr command that runs this script: > while true ; do echo "nothing" > /dev/null ; done This is hysterically funny! Buy two CPUs, then run a program to essentially turn one of them off.
There must be some kind of flaw in the RT scheduling when there are two available processors, maybe it is trying to "spread the load" evenly, causing the RT modules to hop back and forth from one CPU to the other. Maybe that strategy works well for other environments, but EMC2 is such a small system that it backfires in our case. In a remotely related vein, I played around yesterday with upping the servo rate to 5 KHz on my minimill, and was surprised at how little of the tuning changed. I did have to pull down I and D a bit, and the 1/2 F problem was probably worse, as one would expect by reducing the encoder sampling interval by a factor of 5. There was a VERY strong 2.5 KHz tome when the motors were moving at certain speeds, and the PID output had a clear 2.5 KHz component. I am going to have to experiment with a simple filter to remove the highest frequency components from that and see how it works. I think even just averaging the last two samples will help. Jon ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
