Am 23.09.2012 um 18:22 schrieb Kent A. Reed: > On 9/23/2012 3:34 AM, Michael Haberler wrote: >> I just stumbled upon an idea (yet untested) to improve latency with >> RT_PREEMPT on multicore cpu's like the atom >> >> this assumes that rtapi_app in sim mode (plus hal_parport in usermode) will >> be the time-critical component >> it borrows from the isolcpus=1 idea for RTAI where CPU1 would be reserved >> for the base thread >> the idea is to do something similar for rtapi_app: >> >> quote from: Max Krasnyansky's post in >> http://www.digipedia.pl/usenet/thread/19080/11385/ >> >>> Actually this is kind of available right now with vanilla 2.6 kernel. >>> I'm talking about CPU reservation. Here is an example. >>> Let's say we have dual CPU box and we want to dedicate CPU 1 to >>> our application: >>> - Configure the kernel with following boot options: >>> isolcpus=1 acpi_irq_nobalance noirqbalance >>> >>> This excludes CPU 1 from the scheduler balancing logic. And disables >>> ACPI and SW irq balancing. >>> Make sure that you don't run user-space IRQ balancer. >>> >>> - Redirect all interrupts to CPU 0 >>> for i in /proc/irq/*; do >>> echo 1 > $i/smp_affinity; >>> done >>> >>> - Your app call now migrate to CPU 1 >>> int cpu = 1; >>> uint32_t mask = (1 << cpu); >>> sched_setaffinity(0, sizeof(mask), (cpu_set_t *) &mask); >>> >>> That's it. CPU 1 is yours. There will be almost zero activity on it, besides >>> your task of course. >>> >>> Max >> what would needed to be done is to add the sched_setaffinity() code fragment >> to rtapi_app and do the boot/setup incantations before starting linuxcnc >> >> - Michael >> >> > <deleted prior messages in thread> > > Thanks, Michael. > > Despite my waspish comment about custom-building my own kernel, I found > myself doing just that, mostly because I know I'll have to relearn the > process anyway to re-purpose some ARM appliances I have in my toybox. > > Nothing I've done so far in terms of turning off or deleting features > from the kernel has made any noticeable improvement over the distributed > Debian RT kernel, but of course I'm working in profound ignorance of > what's going on inside the Atom processor and the ASUS BIOS. I feel like > Rutherford trying to deduce the nature of atoms by shooting neutrons > into a metal foil. (Yes, the pun is intended; I'm a physicist after all!)
ok, in that case you probably know the famous letter Igor Kapitza had written to Rutherford who was away at a conference, and had forbidden strictly Kapitza (a bona-fide nut case) to engage in any experiments while he was away: "Sir! Our experiment was a total success. We now know how an electric arc with 130 kilo-amperes looks like..." > > Regards, > Kent > > > ------------------------------------------------------------------------------ > Everyone hates slow websites. So do we. > Make your web apps faster with AppDynamics > Download AppDynamics Lite for free today: > http://ad.doubleclick.net/clk;258768047;13503038;j? > http://info.appdynamics.com/FreeJavaPerformanceDownload.html > _______________________________________________ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://ad.doubleclick.net/clk;258768047;13503038;j? http://info.appdynamics.com/FreeJavaPerformanceDownload.html _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
