SCHED_WEAK vs linux regular threads

Julien Blanc julien.blanc at sprinte.eu
Thu Aug 1 15:11:14 CEST 2019


Le jeudi 01 août 2019 à 13:25 +0200, Jan Kiszka a écrit :
> On 01.08.19 11:53, Julien Blanc via Xenomai wrote:
> > Hi,
> > 
> > Let’s say i have four threads :
> > * thread 1, RT, with SCHED_FIFO policy and a sched_param value of
> > 90
> > * thread 2, RT, with SCHED_WEAK policy and a sched_param value of 0
> > * thread 3, RT, with SCHED_WEAK policy and a sched_param value of 0
> 
> Should 2 and 3 have the same parameters in your scenario?

That is not necessary. But our kernel currently lacks OPT_SCHED_WEAK,
so i need to consider whether we need to rebuild and deploy a new one
or not (i’d like to avoid it for now).

> You can assign non-zero prios to thread 2 and 3, ordering it this
> way, but then also while both are in primary mode. For "weak"
> ordering, you could also leave their prio at 0 and play with their
> nice level. That would be a Linux-only "prio".

I’ll give that a try.

Thanks and thanks to Philippe for your detailed answers, this is much
clearer now.

Regards,

Julien




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