> On 24 Jul 2024, at 08:52, Peter Chubb via Devel <devel@sel4.systems> wrote: > >>>>>> "liam" == liam vervecken <liam.vervec...@gmail.com> writes: > > liam> Hello, I'm trying to understand MCS and how the scheduling works > liam> but I'm running into some issues. My setup: RISCV on > liam> BeagleVFire in sel4test > > liam> I have configured 2 threads: > liam> seL4_SchedControl_ConfigureFlags(info->schedcontrol.start, > liam> sched_context_thread2, 1000000, 1000000, 0, 0, 0); > liam> seL4_SchedContext_Bind(sched_context_thread2, thread2_TCB); > > liam> seL4_SchedControl_ConfigureFlags(info->schedcontrol.start, > liam> sched_context_thread3, 1000000, 1000000, 0, 0, 0); > liam> seL4_SchedContext_Bind(sched_context_thread3, thread3_TCB); > > The only times that the seL4 kernel will preempt a running thread are: > -- if a higher priority thread becomes runnable, or > -- if the running thread runs out of budget. > > Your example sets budget==period so no thread will ever run out of > budget and all threads will run until they wait on an event or call > sched_yield(). > > To get the effect you want, set period to twice the budget, so each > thread takes up half the available time.
Nope, that’s not how it’s supposed to work, and if that’s what the implementation does then that’s a bug. A thread should always be preempted if its budget is depleted. A depleted budget is replenished once the new period begins. If budget=period, then that’s immediate. After budget replenishment, the thread should be inserted back at the end of the ready queue. This means, a full budget acts like a normal time slice, with threads of equal priority scheduled round-robin. Gernot _______________________________________________ Devel mailing list -- devel@sel4.systems To unsubscribe send an email to devel-leave@sel4.systems
