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

[Peter Zijlstra]

On Tue, Feb 10, 2026 at 02:18:44PM -0800, Tim Chen wrote:
> From: Chen Yu <yu.c.chen@xxxxxxxxx>
> 
> Introduce an index mapping between CPUs and their LLCs. This provides
> a continuous per LLC index needed for cache-aware load balancing in
> later patches.
> 
> The existing per_cpu llc_id usually points to the first CPU of the
> LLC domain, which is sparse and unsuitable as an array index. Using
> llc_id directly would waste memory.
> 
> With the new mapping, CPUs in the same LLC share a continuous id:
> 
>   per_cpu(llc_id, CPU=0...15)  = 0
>   per_cpu(llc_id, CPU=16...31) = 1
>   per_cpu(llc_id, CPU=32...47) = 2
>   ...
> 
> Once a CPU has been assigned an llc_id, this ID persists even when
> the CPU is taken offline and brought back online, which can facilitate
> the management of the ID.
> 
> Co-developed-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
> Signed-off-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
> Co-developed-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
> Signed-off-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
> Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>

Note that Tim is the one sending this email, so his SOB should be last.
It is also fine to have a SOB occur multiple times in a chain.

Please double check all these SOB chains, because I think this isn't the
first one that isn't right (possibly the very first patch already has
problems).