Yes, the Documentation needs to be fixed first. Setting RR slice to 0 by default could be an option to get the Documentation fixed, but I think Greg setup RR slice to 200ms to avoid mistakes, although NuttX is a RTOS most users will want to use it more like a time sharing system.
This is my supposition, I'm not 100% sure that that was the root cause. BR, Alan On Wed, Nov 26, 2025 at 3:22 PM Matteo Golin <[email protected]> wrote: > I agree with your assessment Tim, it is definitely misleading and should > be improved! > > On Wed, Nov 26, 2025 at 1:17 PM Tim Hardisty <[email protected]> > wrote: > >> OK - but see here: >> https://nuttx.apache.org/docs/latest/reference/user/02_task_scheduling.html >> >> Hardly a "default" if you have to read the help of Kconfig to see what's >> going on? >> >> I know the documentation is, um, lacking...so if it can be improved here >> let's do it! >> >> >> On 26/11/2025 18:12, Alan C. Assis wrote: >> >> There is not a checkbox to ROUND ROBIN in the menuconfig: >> >> [image: image.png] >> >> Only for Sporadic scheduling. The the <Help> for the RR timeslice >> explains it: >> >> │ The round robin timeslice will be set this number of milliseconds; >> │ >> │ Round robin scheduling (SCHED_RR) is enabled by setting this >> │ >> │ interval to a positive, non-zero value. >> >> >> On Wed, Nov 26, 2025 at 3:07 PM Matteo Golin <[email protected]> >> wrote: >> >>> I suppose I would agree, that does seem misleading if the default is RR. >>> Does the RR scheduling on NuttX have priority-based preemption/priority >>> inversion avoidance mechanisms? Maybe that could be the reasoning for >>> the wording. >>> >>> On Wed, Nov 26, 2025 at 1:00 PM Tim Hardisty <[email protected]> >>> wrote: >>> >>> > That's what I inferred (yet to try it) - so is the documentation >>> > misleading since the default CONFIG_RR_INTERVAL=200 forces RR >>> scheduling >>> > rather than the stated "strict priority scheduling"? >>> > >>> > On 26/11/2025 17:54, Alan C. Assis wrote: >>> > > CONFIG_RR_INTERVAL=0 >>> > > >>> > > On Wed, Nov 26, 2025 at 2:22 PM Tim Hardisty < >>> [email protected]> >>> > > wrote: >>> > > >>> > >> Apologies if this isn't really a NuttX question... >>> > >> >>> > >> Documentation says "By default, NuttX performs strict priority >>> > scheduling". >>> > >> >>> > >> Default CONFIG_RR_INTERVAL is 200ms. >>> > >> >>> > >> I have multiple threads, but have not set any scheduling >>> parameters, but >>> > >> it seems threads are being scheduled every 200ms rather on a >>> priority >>> > >> basis. >>> > >> >>> > >> What *should* I be doing, please, to get all my threads scheduled by >>> > >> priority? >>> > >> >>> > >> Thanks, >>> > >> >>> > >> TimH >>> > >> >>> > >> PS - yes I have thrown myself in the deep end without a life jacket >>> with >>> > >> my project. And I'm no doubt up ****-creek without a paddle. But I >>> am >>> > >> always learning! >>> > >> >>> > >>> >>
