Subject: Re: [PATCH v2 1/3] powerpc/numa: Introduce logical numa id

From: Srikar Dronamraju <[email-masked]>
Date: Mon, 17 Aug 2020 16:29:50 +0530

* Aneesh Kumar K.V <[email-masked]> [2020-08-17 16:02:36]:

> We use ibm,associativity and ibm,associativity-lookup-arrays to derive the numa
> node numbers. These device tree properties are firmware indicated grouping of
> resources based on their hierarchy in the platform. These numbers (group id) are
> not sequential and hypervisor/firmware can follow different numbering schemes.
> For ex: on powernv platforms, we group them in the below order.
> 
>  *     - CCM node ID
>  *     - HW card ID
>  *     - HW module ID
>  *     - Chip ID
>  *     - Core ID
> 
> Based on ibm,associativity-reference-points we use one of the above group ids as
> Linux NUMA node id. (On PowerNV platform Chip ID is used). This results
> in Linux reporting non-linear NUMA node id and which also results in Linux
> reporting empty node 0 NUMA nodes.
> 
> This can  be resolved by mapping the firmware provided group id to a logical Linux
> NUMA id. In this patch, we do this only for pseries platforms considering the
> firmware group id is a virtualized entity and users would not have drawn any
> conclusion based on the Linux Numa Node id.
> 
> On PowerNV platform since we have historically mapped Chip ID as Linux NUMA node
> id, we keep the existing Linux NUMA node id numbering.

I still dont understand how you are going to handle numa distances.
With your patch, have you tried dlpar add/remove on a sparsely noded machine?

-- 
Thanks and Regards
Srikar Dronamraju