On Tue, Oct 15, 2024 at 05:31:09PM +0200, Andrea Righi wrote: ... > > - For the purpose of determining whether a CPU is idle for e.g. task > > placement from ops.select_cpu(). The CPU *should* be considered idle in > > this polling state. > > > > Overall, it feels a bit contrived to generate update_idle() events > > consecutively for this. If a scheduler wants to poll in idle state, can't it > > do something like the following? > > > > - Trigger kick from update_idle(cpu, true) and remember that the CPU is in > > the polling state. > > > > - Keep kicking from ops.dispatch() until polling state is cleared. > > > > As what kick() guarnatees is at least one dispatch event after kicking, this > > is guaranteed to be correct and the control flow, while a bit more > > complicated, makes sense - it triggers dispatch on idle transition and keeps > > dispatching in the idle state. > > > > What do you think? > > That seems to work in theory, I'll run some tests to confirm that it > also works in practice. :) > > It looks definitely nicer than triggering multiple ops.update_idle() > from the kernel and we can maintain the proper semantic of triggering > update_idle() only on actual idle state changes. For the record, this seems to be working for now. Here is the implementation of the idea proposed by Tejun: https://github.com/sched-ext/scx/commit/40ccca8cbef8fc73e16bfb789c7565326b3cca62 Therefore, we can ignore the kernel patch. Thanks for the help on this! -Andrea
