Re: [RFC PATCH v4 08/28] sched: Set up LLC indexing

[Chen, Yu C]

On 9/29/2025 6:43 PM, Adam Li wrote:
> On 9/26/2025 9:51 PM, Chen, Yu C wrote:
> > Hi Adam,
> >
> > On 9/26/2025 2:14 PM, Adam Li wrote:

[snip]
> > >    #ifdef CONFIG_SCHED_CACHE
> > > -       if (llc_has_parent_sd && multi_llcs_node && !sched_asym_cpucap_active())
> > > +       if (has_llc && llc_has_parent_sd && multi_llcs_node &&
> >
> > multi_llcs_node will be false if there is no SD_SHARE_LLC domain on the
> > platform, so I suppose we don’t have to introduce has_llc?
> > multi_llcs is set to true iff there are more than 1 SD_SHARE_LLC domains under its
> > SD_SHARE_LLC parent domain.
>
> If there is *no* SD_SHARE_LLC domain, my test shows 'multi_llcs_node' is still 1 (true).
>
> Looks it is because the default value of 'multi_llcs_node' is 1.
>
> build_sched_domains():
> 	unsigned int multi_llcs_node = 1;
>
> And this condition is always false since we have no SD_SHARE_LLC domain,
> therefore 'multi_llcs_node' will not be changed:
>
>                          if (!(sd->flags & SD_SHARE_LLC) && child &&
>                              (child->flags & SD_SHARE_LLC))

I see. I was looking at the v5 internal version where
multi_llcs was initialized to 0. Let me double check
and refine the logic. Thanks!

Chenyu


> Thanks,
> -adam