linux-kernel - Re: [RFC PATCH 1/2] NUMA balancing: fix NUMA topology type for memory tiering system

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Date:   Fri, 28 Jan 2022 10:53:45 +0530
From:   Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:     Huang Ying <ying.huang@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Mel Gorman <mgorman@...e.de>, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>, Rik van Riel <riel@...riel.com>
Subject: Re: [RFC PATCH 1/2] NUMA balancing: fix NUMA topology type for
 memory tiering system

* Huang Ying <ying.huang@...el.com> [2022-01-28 10:38:41]:

> 
> One possible fix is to ignore CPU-less nodes when detecting NUMA
> topology type in init_numa_topology_type().  That works well for the
> example system.  Is it good in general for any system with CPU-less
> nodes?
> 

A CPUless node at the time online doesn't necessarily mean a CPUless node
for the entire boot. For example: On PowerVM Lpars, aka powerpc systems,
some of the nodes may start as CPUless nodes and then CPUS may get
populated/hotplugged on them.

Hence I am not sure if adding a check for CPUless nodes at node online may
work for such systems.

> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
> Suggested-by: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Rik van Riel <riel@...riel.com>
> Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> ---
>  kernel/sched/topology.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 

-- 
Thanks and Regards
Srikar Dronamraju