Re: [PATCH v4 1/7] sched/fair: default to false in test_idle_cores

[Abel Wu]

Hi Josh, thanks for your comments!

On 6/28/22 6:53 AM, Josh Don Wrote:
> On Sun, Jun 19, 2022 at 5:05 AM Abel Wu <wuyun.abel@xxxxxxxxxxxxx> wrote:
> > It's uncertain whether idle cores exist or not if shared sched-domains
> > are not ready, so returning "no idle cores" usually makes sense.
> >
> > While __update_idle_core() is an exception, it checks status of this
> > core and set to shared sched-domain if necessary. So the whole logic
> > depends on the existence of shared domain, and can bail out early if
> > it isn't available. Modern compilers seems capable of handling such
> > cases, so remove the tricky self-defined default return value.
>
> I don't think the compiler will be able to bail out of the smt
> iteration early, since it'll have to do another rcu dereference for
> the sd_llc in set(). But I also don't think this case needs
> optimization, since it should be transient while the domain isn't
> ready.
>
> Reviewed-by: Josh Don <joshdon@xxxxxxxxxx>

Obviously I failed to comprehend the difference between the changed
assembly code, my bad..

Thanks,
Abel