#linuxcnc-devel Logs

Sep 16 2017

04:02 PM memfrob: I got RTAI working with NO_HZ_FULL finally! Latency is much, much better. 23120ns tops even launching firefox which would usually make it spike to around 40k ns on the same system
04:03 PM memfrob: I still get overruns though with RTAI 5 for no apparent reason which makes it jump to 100k ns but other people are having the same issue according to the RTAI mailing list
04:05 PM memfrob: Polluting the kernel hacking section with enabling all the debug options have no impact, I've tried countless combinations including several RCU and PREEMPT options.
04:06 PM memfrob: On average though, 500-2000 ns
04:07 PM memfrob: Lowest I ever seen on my end, this NO_HZ option is sweet!
07:03 PM KimK: memfrob: Thanks to you and CaptHindsight for working on this! I'll look forward to trying it, but not immediately, as I am frying other fish right now. Besides, maybe it's not quite ripe yet?
07:06 PM * KimK "plunks" RTAI 5: ..Plunk, plunk, plunk... Hmmm, no, not ripe yet. (What, that's not how you do it?)
07:25 PM memfrob: KimK, currently backporting about a hundred patches from the 4.4 series to fix all the issues with NO_HZ right now
07:26 PM memfrob: overflows are completely unrelated but it doesn't hurt to backport fixes for the timer/timekeeping stuff
07:26 PM memfrob: the latency spikes are an issue with RTAI 5(0.1) mainline
07:27 PM memfrob: After kernel 4.1 is all fixed up and patched up, (it's already countless times more stable than the hal-linux patch included with the official RTAI 5.0.1 tarball) I'll move on to 4.4 and 4.9
07:28 PM KimK: Well, it's really excellent that you're working on this. RTAI has been trusted a long time. If it needs to evolve, fine, but I hate to see it go away altogether. So, thanks for working on it.
07:28 PM memfrob: To my knowledge (the CVS repo is down because gna is dead) there is no 4.9 support for RTAI but I'm keeping RTAI as close as I can to the real IPIPE code.
07:29 PM memfrob: Keeping it in-line with Xenomai/IPIPE does two things. Makes it cleaner and easier to work with, and fixes whatever bugs that are introduced into the official RTAI tree.
07:29 PM KimK: gna?
07:29 PM memfrob: https://en.wikipedia.org/wiki/Gna!
07:29 PM KimK: Thanks.
07:31 PM memfrob: I must have more free-time than the Xenomai developers because even the official patches are a bit wonky, hence all the backporting. WIth git cherry-pick and git.kernel it's pretty easy to build on it though.
07:31 PM memfrob: git.kernel.org ^
07:32 PM memfrob: I'm glad someone is interested because a lot of my RTAI work, as good as it is, is often completely ignored. It's for my own use but if it helps someone else out too, that's great!
07:33 PM KimK: I suppose it would have been against the Gnu charter to just move Gna everything to Github? Oh, well.
07:35 PM memfrob: I'm just glad I get advice here otherwise it wouldn't be possible. For many years, the issue with RTAI was issues with math handling and it was all a mystery until jepler was able to pin-point it down to SSE/SSE2. Now I just force -msse -msse2 in the CFLAGS and issues with sincos no longer _sometimes_ depend on the phase of the moon.
07:35 PM KimK: "Hope you've been keeping your local git repo updated, because you're on your own now! Bye! (click)." Sheesh, what a deal.
07:36 PM memfrob: Yeah I have no idea how long until the RTAI repo is back online. They used CVS up until Gna went down and nobody has been able to grab code except for the tarballs.
07:37 PM memfrob: Github's API is open source though, not sure if it's GPL'd or not.
07:38 PM KimK: Well, maybe not all bad news then. (From the "take your lemons and make lemonade" department?) At least with a tarball (and a git tag) everybody's got a good re-starting point.
07:39 PM memfrob: Indeed, that's what I'm doing.
07:39 PM memfrob: As long as there's no drastic changes in whitespace all the sudden. It's been a kludge of tabs and spaces since the beginning.
07:40 PM memfrob: Who codes with tabs _and_ spaces.. -_-
07:40 PM memfrob: That's almost as bad as using Notepad in Wine to do all your work.
07:40 PM KimK: Hah!
07:41 PM memfrob: You seen this? https://www.youtube.com/watch?v=SsoOG6ZeyUI
07:50 PM KimK: Ha, I have now. And their argument continues in the comments. Funny.
07:52 PM KimK: Oops, got to go, but keep us posted on your progress. I always scroll back and catch up.
08:02 PM memfrob: Whelp I just finished cherry-picking stuff from 4.4.88 (latest) synced these files from 4.1.43 to that release: include/linux/tick.h kernel/time/hrtimer.c kernel/time/tick-sched.c kernel/time/tick-sched.h
08:05 PM memfrob: and now kernel/time/time.c
08:39 PM memfrob: kernel/time/timekeeping.c synced
08:40 PM memfrob: and kernel/time/ntp.c -- now to build and test
09:44 PM memfrob: Just needs some include fixes but all the sched/tick/time stuff is sorted out. break time!