linux-kernel - Re: [PATCH v3 2/2] mm: memory_hotplug: drop memoryless node from fallback lists

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Message-ID: <87bkctg4f4.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date:   Fri, 20 Oct 2023 15:05:03 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Qi Zheng <zhengqi.arch@...edance.com>
Cc:     akpm@...ux-foundation.org, rppt@...nel.org, david@...hat.com,
        vbabka@...e.cz, mhocko@...e.com, willy@...radead.org,
        mgorman@...hsingularity.net, mingo@...nel.org,
        aneesh.kumar@...ux.ibm.com, hannes@...xchg.org, osalvador@...e.de,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 2/2] mm: memory_hotplug: drop memoryless node from
 fallback lists

Qi Zheng <zhengqi.arch@...edance.com> writes:

> In offline_pages(), if a node becomes memoryless, we
> will clear its N_MEMORY state by calling node_states_clear_node().
> But we do this after rebuilding the zonelists by calling
> build_all_zonelists(), which will cause this memoryless node to
> still be in the fallback list of other nodes.

For fallback list, do you mean pgdat->node_zonelists[]?  If so, in

build_all_zonelists
  __build_all_zonelists
    build_zonelists
      build_zonelists_in_node_order
        build_zonerefs_node

populated_zone() will be checked before adding zone into zonelist.

So, IIUC, we will not try to allocate from the memory less node.

--
Best Regards,
Huang, Ying


> This will incur
> some runtime overhead.
>
> To drop memoryless node from fallback lists in this case, just
> call node_states_clear_node() before calling build_all_zonelists().
>
> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
> Acked-by: David Hildenbrand <david@...hat.com>

[snip]

--
Best Regards,
Huang, Ying