On Sat, Mar 9, 2013 at 12:12 PM, Vin Shelton <a...@alumni.princeton.edu> wrote: > On Fri, Mar 8, 2013 at 10:28 PM, Bruce Ashfield > <bruce.ashfi...@windriver.com> wrote: >> On 13-03-08 5:36 PM, David Mulder wrote: >>> I’m running a 10us control loop by (under vxWorks) setting one thread’s >>> priority to max and not yielding ever (letting other tasks run on other >>> cores), but Linux seems to thwart that capability: Ubuntu swaps out my >>> thread occasionally for hundreds of microseconds; Yocto prints a >>> “[sched_delayed] sched: RT throttling activated” message as soon as I >>> start my thread, so it seems likely that it will swap out my thread >>> periodically (I’m not quite able to confirm that yet), and even the >>> fastest thread swap that I’ve heard of is too slow. >> >> >> You are looking for kernel functionality that doesn't exist yet. In >> any SMP system there are sources of cross cpu interference that can't >> be removed, if you do, the global state machines of the kernel will >> break and the system will eventually come to a halt. >> >> The system is trying to save you from yourself, by throttling the >> RT task from taking the entire system down. >> >> There is work in the mainline kernel and -rt communities around cpu >> and cpu isolation (some of which we'll try and make available via >> the yocto meta-virtualization or meta-realtime layer, when they are >> ready), it goes by names such as task_nohz or adaptive_nohz. It's >> a complex problem to solve (interrupts, rcu, lapic), and there's not >> likely to be anything available in the short term. > > At ELC, Steve Rostedt said that this feature is currently targeted at > the June mainline kernel release, but there's a lot of work still to > be done, so that's not a firm date.
Absolutely. There's no such thing as a firm date for anything, I (among others) are following the development closely, testing, and helping wherever possible. Cheers, Bruce > > Regards, > Vin Shelton > _______________________________________________ > yocto mailing list > yocto@yoctoproject.org > https://lists.yoctoproject.org/listinfo/yocto -- "Thou shalt not follow the NULL pointer, for chaos and madness await thee at its end" _______________________________________________ yocto mailing list yocto@yoctoproject.org https://lists.yoctoproject.org/listinfo/yocto
