linux-kernel - Re: [PATCH] x86/numa: move setting parse numa node to num_add

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Message-ID: <5A1EB57B.2080101@huawei.com>
Date:   Wed, 29 Nov 2017 21:26:19 +0800
From:   zhong jiang <zhongjiang@...wei.com>
To:     Michal Hocko <mhocko@...nel.org>
CC:     <tglx@...utronix.de>, <mingo@...hat.com>, <x86@...nel.org>,
        <lenb@...nel.org>, <akpm@...ux-foundation.org>, <vbabka@...e.cz>,
        <linux-mm@...ck.org>, <richard.weiyang@...il.com>,
        <pombredanne@...b.com>, <linux-kernel@...r.kernel.org>,
        <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH] x86/numa: move setting parse numa node to num_add_memblk

On 2017/11/29 21:01, Michal Hocko wrote:
> On Wed 29-11-17 20:41:25, zhong jiang wrote:
>> On 2017/11/29 20:03, Michal Hocko wrote:
>>> On Wed 29-11-17 17:13:27, zhong jiang wrote:
>>>> Currently, Arm64 and x86 use the common code wehn parsing numa node
>>>> in a acpi way. The arm64 will set the parsed node in numa_add_memblk,
>>>> but the x86 is not set in that , then it will result in the repeatly
>>>> setting. And the parsed node maybe is  unreasonable to the system.
>>>>
>>>> we would better not set it although it also still works. because the
>>>> parsed node is unresonable. so we should skip related operate in this
>>>> node. This patch just set node in various architecture individually.
>>>> it is no functional change.
>>> I really have hard time to understand what you try to say above. Could
>>> you start by the problem description and then how you are addressing it?
>>   I am so sorry for that.  I will make the issue clear.
>>  
>>   Arm64  get numa information through acpi.  The code flow is as follows.
>>
>>   arm64_acpi_numa_init
>>        acpi_parse_memory_affinity
>>           acpi_numa_memory_affinity_init
>>               numa_add_memblk(nid, start, end);      //it will set node to numa_nodes_parsed successfully.
>>               node_set(node, numa_nodes_parsed);     // numa_add_memblk had set that.  it will repeat.
>>
>>  the root cause is that X86 parse numa also  go through above code.  and  arch-related
>>  numa_add_memblk  is not set the parsed node to numa_nodes_parsed.  it need
>>  additional node_set(node, numa_parsed) to handle.  therefore,  the issue will be introduced.
>>
> No it is not much more clear. I would have to go and re-study the whole
> code flow to see what you mean here. So you could simply state what _the
> issue_ is? How can user observe it and what are the consequences?
  The patch do not fix a real issue.  it is a cleanup.
  because the acpi code  is public,  I find they are messy between
  Arch64 and X86 when parsing numa message .  therefore,  I try to
  make the code more clear between them.

  Thanks
  zhongjiang
> Sorry for my laziness, I could go and read the code but the primary
> point of the changelog is to be _clear_ about the problem and the fix.
> Call paths can help reviewers but the scope should be clear even without
> them.