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SubjectRe: [RFC PATCH V4 1/1] mm: add last level page table numa info to /proc/pid/numa_pgtable
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On 04.08.22 10:04, haoxin wrote:
>
> 在 2022/8/1 下午9:28, David Hildenbrand 写道:
>> On 01.08.22 14:17, Xin Hao wrote:
>>> In many data center servers, the shared memory architectures is
>>> Non-Uniform Memory Access (NUMA), remote numa node data access
>>> often brings a high latency problem, but what we are easy to ignore
>>> is that the page table remote numa access, It can also leads to a
>>> performance degradation.
>> Let me try rewriting:
>>
>> "
>> Many data center servers employ Non-Uniform Memory Access (NUMA)
>> architectures. Remote numa memory access results in high latency. While
>> memory placement is one issue, sub-optimal page table placement can also
>> result in surprise performance degradation.
>> "
> Thanks,  it reads more clearly.
>
>>> So there add a new interface in /proc, This will help developers to
>>> get more info about performance issues if they are caused by cross-NUMA.
>>
>> Why do we only care about "last level page table", why not about the others?
>>
>> IMHO, we could emit something like "0, 1, 3, 0" instead for a given user
>> space address, showing the NUMA node the page table belongs to from
>> highest to lowest page table level.
>
> I have planned to implement the PTE page table in this version first, 
> and then support other page tables in the next patch later.

If there are plans, let's do it all at once, to get a good and single
interface to expose that information.

--
Thanks,

David / dhildenb

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