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Message-ID: <790a89e6-93ee-dd43-a785-495ab52a2dde@bytedance.com>
Date:   Fri, 20 Oct 2023 17:09:37 +0800
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Subject: Re: [PATCH v3 1/2] mm: page_alloc: skip memoryless nodes entirely
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To:     Ingo Molnar <mingo@kernel.org>
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
References: <cover.1697711415.git.zhengqi.arch@bytedance.com>
 <157013e978468241de4a4c05d5337a44638ecb0e.1697711415.git.zhengqi.arch@bytedance.com>
 <ZTI6zM0MUlfglkD+@gmail.com>
From:   Qi Zheng <zhengqi.arch@bytedance.com>
In-Reply-To: <ZTI6zM0MUlfglkD+@gmail.com>
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On 2023/10/20 16:31, Ingo Molnar wrote:
> 
> * 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

Will fix the typos above.

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

Thanks.

> 
> Thanks,
> 
> 	Ingo