Re: [PATCH v3 04/21] sched/cache: Make LLC id continuous

[Chen, Yu C]

Hi Peter,

On 2/19/2026 11:40 PM, Peter Zijlstra wrote:
> On Mon, Feb 16, 2026 at 01:14:20PM +0530, K Prateek Nayak wrote:

[ ... ]

> > +static int __sched_domains_alloc_llc_id(void)
> > +{
> > +	int lid;
> > +
> > +	lockdep_assert_held(&sched_domains_mutex);
> > +
> > +	lid = cpumask_first_zero(sched_domains_llc_id_allocmask);
> > +	if (lid >= tl_max_llcs)
> > +		tl_max_llcs++;
>
> Urgh,. should we not rather track the max lid?

Do you mean we should not always increment the max lid,
but instead decrease it when an llc_id is released?
I think Tim has adjusted the code to shrink tl_max_llcs
when an llc_id is released:
https://lore.kernel.org/all/acc7a5c96e8235bf11af640798ce1b60bcaa8196.camel@xxxxxxxxxxxxxxx/

> Also, we allocate max_llc sized data structures, if this thing is
> 'variable' we must also always store a copy of the 'lid' size of the
> time of allocation.

Do you mean we should save the latest llc_max in the sched_domain
and publish it during sd attachment, as suggested at:

https://lore.kernel.org/all/20260220104533.GO1395266@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/

thanks,
Chenyu