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From:   "Huang, Ying" <ying.huang@intel.com>
To:     Qi Zheng <zhengqi.arch@bytedance.com>
Cc:     akpm@linux-foundation.org, rppt@kernel.org, david@redhat.com,
        vbabka@suse.cz, mhocko@suse.com, willy@infradead.org,
        mgorman@techsingularity.net, mingo@kernel.org,
        aneesh.kumar@linux.ibm.com, hannes@cmpxchg.org, osalvador@suse.de,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v3 2/2] mm: memory_hotplug: drop memoryless node from
 fallback lists
In-Reply-To: <9f1dbe7ee1301c7163b2770e32954ff5e3ecf2c4.1697711415.git.zhengqi.arch@bytedance.com>
        (Qi Zheng's message of "Thu, 19 Oct 2023 18:43:55 +0800")
References: <cover.1697711415.git.zhengqi.arch@bytedance.com>
        <9f1dbe7ee1301c7163b2770e32954ff5e3ecf2c4.1697711415.git.zhengqi.arch@bytedance.com>
Date:   Fri, 20 Oct 2023 15:05:03 +0800
Message-ID: <87bkctg4f4.fsf@yhuang6-desk2.ccr.corp.intel.com>
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Qi Zheng <zhengqi.arch@bytedance.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@bytedance.com>
> Acked-by: David Hildenbrand <david@redhat.com>

[snip]

--
Best Regards,
Huang, Ying