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Sender: Ingo Molnar <mingo.kernel.org@gmail.com>
Date:   Fri, 20 Oct 2023 10:31:08 +0200
From:   Ingo Molnar <mingo@kernel.org>
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, aneesh.kumar@linux.ibm.com,
        ying.huang@intel.com, hannes@cmpxchg.org, osalvador@suse.de,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v3 1/2] mm: page_alloc: skip memoryless nodes entirely
Message-ID: <ZTI6zM0MUlfglkD+@gmail.com>
References: <cover.1697711415.git.zhengqi.arch@bytedance.com>
 <157013e978468241de4a4c05d5337a44638ecb0e.1697711415.git.zhengqi.arch@bytedance.com>
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* Qi Zheng <zhengqi.arch@bytedance.com> wrote:

> In find_next_best_node(), We skipped the memoryless nodes

s/We
 /we

s/the memoryless nodes
 /memoryless nodes

> when building the zonelists of other normal nodes (N_NORMAL),
> but did not skip the memoryless node itself when building
> the zonelist. This will cause it to be traversed at runtime.
> 
> For example, say we have node0 and node1, node0 is memoryless
> node, then the fallback order of node0 and node1 as follows:
> 
> [    0.153005] Fallback order for Node 0: 0 1
> [    0.153564] Fallback order for Node 1: 1
> 
> After this patch, we skip memoryless node0 entirely, then
> the fallback order of node0 and node1 as follows:

s/fallback
 /fall back

> 
> [    0.155236] Fallback order for Node 0: 1
> [    0.155806] Fallback order for Node 1: 1
> 
> So it becomes completely invisible, which will reduce runtime
> overhead.
> 
> And in this way, we will not try to allocate pages from memoryless
> node0, then the panic mentioned in [1] will also be fixed. Even though
> this problem has been solved by dropping the NODE_MIN_SIZE constrain
> in x86 [2], it would be better to fix it in core MM as well.

s/in core MM
 /in the core MM

> [1]. https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/
> [2]. https://lore.kernel.org/all/20231017062215.171670-1-rppt@kernel.org/
> 
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
> Acked-by: David Hildenbrand <david@redhat.com>

> +	/*
> +	 * Use the local node if we haven't already. But for memoryless local
> +	 * node, we should skip it and fallback to other nodes.

s/fallback
 /fall back

s/already. But
 /already, but

Acked-by: Ingo Molnar <mingo@kernel.org>

Thanks,

	Ingo