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Date:   Mon, 12 Oct 2020 15:22:42 +0000 (UTC)
From:   Christopher Lameter <cl@linux.com>
To:     Xianting Tian <tian.xianting@h3c.com>
cc:     penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com,
        akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, kuba@kernel.org,
        alexei.starovoitov@gmail.com
Subject: Re: [PATCH] mm: Make allocator take care of memoryless numa node
In-Reply-To: <20201012082739.15661-1-tian.xianting@h3c.com>
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References: <20201012082739.15661-1-tian.xianting@h3c.com>
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On Mon, 12 Oct 2020, Xianting Tian wrote:

> In architecture like powerpc, we can have cpus without any local memory
> attached to it. In such cases the node does not have real memory.
>
> In many places of current kernel code, it doesn't judge whether the node is
> memoryless numa node before calling allocator interface.

That is intentional. SLUB relies on the page allocator to pick a node.

> This patch is to use local_memory_node(), which is guaranteed to have
> memory, in allocator interface. local_memory_node() is a noop in other
> architectures that don't support memoryless nodes.

The patch would destroy the support for memory policies in the
SLUB allocator and likely in the other ones as well.