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Date:   Wed, 29 Nov 2017 20:41:25 +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 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.

  menawhile,  the parsed node is meaningless when numa_add_memblk fails and return 0.
 so we should bail out in time.
 
is it a little clearer ?

 Thanks
 zhongjiang
>> Signed-off-by: zhong jiang <zhongjiang@...wei.com>
>> ---
>>  arch/x86/mm/amdtopology.c | 1 -
>>  arch/x86/mm/numa.c        | 3 ++-
>>  drivers/acpi/numa.c       | 5 ++++-
>>  3 files changed, 6 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/mm/amdtopology.c b/arch/x86/mm/amdtopology.c
>> index 91f501b..7657042 100644
>> --- a/arch/x86/mm/amdtopology.c
>> +++ b/arch/x86/mm/amdtopology.c
>> @@ -151,7 +151,6 @@ int __init amd_numa_init(void)
>>  
>>  		prevbase = base;
>>  		numa_add_memblk(nodeid, base, limit);
>> -		node_set(nodeid, numa_nodes_parsed);
>>  	}
>>  
>>  	if (!nodes_weight(numa_nodes_parsed))
>> diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
>> index 25504d5..8f87f26 100644
>> --- a/arch/x86/mm/numa.c
>> +++ b/arch/x86/mm/numa.c
>> @@ -150,6 +150,8 @@ static int __init numa_add_memblk_to(int nid, u64 start, u64 end,
>>  	mi->blk[mi->nr_blks].end = end;
>>  	mi->blk[mi->nr_blks].nid = nid;
>>  	mi->nr_blks++;
>> +
>> +	node_set(nid, numa_nodes_parsed);
>>  	return 0;
>>  }
>>  
>> @@ -693,7 +695,6 @@ static int __init dummy_numa_init(void)
>>  	printk(KERN_INFO "Faking a node at [mem %#018Lx-%#018Lx]\n",
>>  	       0LLU, PFN_PHYS(max_pfn) - 1);
>>  
>> -	node_set(0, numa_nodes_parsed);
>>  	numa_add_memblk(0, 0, PFN_PHYS(max_pfn));
>>  
>>  	return 0;
>> diff --git a/drivers/acpi/numa.c b/drivers/acpi/numa.c
>> index 917f1cc..f2e33cb 100644
>> --- a/drivers/acpi/numa.c
>> +++ b/drivers/acpi/numa.c
>> @@ -294,7 +294,9 @@ void __init acpi_numa_slit_init(struct acpi_table_slit *slit)
>>  		goto out_err_bad_srat;
>>  	}
>>  
>> -	node_set(node, numa_nodes_parsed);
>> +	/* some architecture is likely to ignore a unreasonable node */
>> +	if (!node_isset(node, numa_nodes_parsed))
>> +		goto out;
>>  
>>  	pr_info("SRAT: Node %u PXM %u [mem %#010Lx-%#010Lx]%s%s\n",
>>  		node, pxm,
>> @@ -309,6 +311,7 @@ void __init acpi_numa_slit_init(struct acpi_table_slit *slit)
>>  
>>  	max_possible_pfn = max(max_possible_pfn, PFN_UP(end - 1));
>>  
>> +out:
>>  	return 0;
>>  out_err_bad_srat:
>>  	bad_srat();
>> -- 
>> 1.8.3.1


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