On Tuesday, January 31, 2012 07:22:16 PM Kent A. Reed did opine: > <I'm backtracking a bit> > > On 1/31/2012 10:49 AM, gene heskett wrote: > > On Tuesday, January 31, 2012 09:53:43 AM andy pugh did opine: > >> > On 31 January 2012 16:36, gene heskett<ghesk...@wdtv.com> wrote: > >>> > > In grub, if the rtai kernel line has "isolcpus=1" appended, > >>> > > which takes cpu1 out of the scheduler, then after the boot in > >>> > > completed, everything is running on cpu0. > >>> > > > >>> > > Then, using taskset, put emc/linuxcnc to running on the now > >>> > > forcibly idled cpu1. > >> > > >> > I thought LinuxCNC did this automatically if isolcpus was set? > > > > Apparently it does not, at least not on my box, Andy. There is a line > > in the dmsg output that seems to indicate it is aware of isolcpus, > > but IMO its wrong. In fact I'll look and see if taskset's use fixes > > that right now. No, that line: > > > > RTAI[hal]: mounted (IPIPE-NOTHREADS, IMMEDIATE (INTERNAL IRQs > > DISPATCHED), ISOL_CPUS_MASK: 0). > > Gene: > > I haven't spent enough time in the RTAI source code to know just what > ISOL_CPUS_MASK means and what it causes to happen or not happen. Perhaps > this will turn out to be a vital clue but I don't know how to interpret > it. > > As for Andy's reply, what LinuxCNC does automatically is start up the > *realtime* processes on the isolated cpu1, not all of LinuxCNC. Many > processes are started on cpu0 as you can see using, e.g., htop. These > might include axis, milltask, etc. My copy of htop from the repo's doesn't report which core a process is running on. Is there some option switch I can set?
> On my ASUS board right now, running 2.6.32-122-rtai kernel with > isolcpus=1, I started htop. I started the do-nothing, loop-forever "cpu > hog", which drove the cpu0 usage to 100.0% and keeps it there. I started > LinuxCNC 2.4.6 with the 3-axis mill simulation. I started Firefox for > good measure. According to htop, I'm consuming about 430MB out of 2003MB > of RAM, while the cpu hog accounts for roughly 50% of cpu usage, axis > roughly 25% and everything else is less. cpu1 usage, of course, is > registering 0.0% (except for a sub-1% perturbation once in a while). > (Incidently, I also see the "ISOL_CPUS_MASK: 0" message). > > Response to the PS/2 mouse and keyboard remains satisfactory. I can move > windows, surf the internet, click buttons in axis, etc. No problem. > > If I kill LinuxCNC and invoke the latency-test instead, memory usage > drops about 30MB while cpu0 usage remains at 100.0% as expected. Now the > lion's share is consumed by the cpu hog because there's nothing to > compete with it. The reported latency jitter numbers are excellent, > slightly less than 2000 nanoseconds. > > I'm thinking about your remark that the behavior (on your system) of the > two pre-release builds has changed recently. > > Did this change of behavior occur after you brought up your two-way NFS > services? I'm wondering if you're sacrificing cycles to an angry NFS > god. What does htop say? No, it continued to run well, albeit at a 65 u-sec base-thread, for at least a day after I had the 2nd, back path running too. > I'll try later to pull down a pre-release 2.6.0 build and see if that > changes the picture for me, but so far I haven't been able to replicate > the isolcpus-related portion of your original problem statement. The > probing problem is a different kettle of fish. Fortunately you've got > really good folk looking after that one. > > Regards, > Kent > Thanks Kent. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> A wise person makes his own decisions, a weak one obeys public opinion. -- Chinese proverb ------------------------------------------------------------------------------ Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
