linux-kernel - Re: [PATCH] mm: Make allocator take care of memoryless numa node

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Date:   Mon, 12 Oct 2020 15:22:42 +0000 (UTC)
From:   Christopher Lameter <cl@...ux.com>
To:     Xianting Tian <tian.xianting@....com>
cc:     penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kuba@...nel.org,
        alexei.starovoitov@...il.com
Subject: Re: [PATCH] mm: Make allocator take care of memoryless numa node

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.