linux-kernel - Re: [PATCH 2/2 v6] mm/mempolicy: Don't create weight sysfs for memoryless nodes

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Message-ID: <ed0004ea-c8d6-4ba9-ba40-0c9a97d98db6@sk.com>
Date: Tue, 18 Mar 2025 20:02:46 +0900
From: Honggyu Kim <honggyu.kim@...com>
To: Yunjeong Mun <yunjeong.mun@...com>, Gregory Price <gourry@...rry.net>
Cc: kernel_team@...ynix.com, Joshua Hahn <joshua.hahnjy@...il.com>,
 harry.yoo@...cle.com, ying.huang@...ux.alibaba.com,
 gregkh@...uxfoundation.org, rakie.kim@...com, akpm@...ux-foundation.org,
 rafael@...nel.org, lenb@...nel.org, dan.j.williams@...el.com,
 Jonathan.Cameron@...wei.com, dave.jiang@...el.com, horen.chuang@...ux.dev,
 hannes@...xchg.org, linux-kernel@...r.kernel.org,
 linux-acpi@...r.kernel.org, linux-mm@...ck.org, kernel-team@...a.com
Subject: Re: [PATCH 2/2 v6] mm/mempolicy: Don't create weight sysfs for
 memoryless nodes



On 3/18/2025 5:02 PM, Yunjeong Mun wrote:
> Hi Gregory, I have one more question below.
> 
> On Tue, 11 Mar 2025 00:42:49 -0400 Gregory Price <gourry@...rry.net> wrote:
>> On Tue, Mar 11, 2025 at 01:02:07PM +0900, Yunjeong Mun wrote:
>>
>> forenote - Hi Andrew, please hold off on the auto-configuration patch
>> for now, the sk group has identified a hotplug issue we need to work out
>> and we'll likely need to merge these two patch set together.  I really
>> appreciate your patience with this feature.
>>
>>> Hi Gregory,
>>>
>>> In my understanding, the reason we are seeing 12 NUMA node is because
>>> it loops through node_states[N_POSSIBLE] and its value is 4095 (twelves ones)
>>> in the code [1]  below:
>>>
>> ... snip ...
>>
>> Appreciated, so yes this confirms what i thought was going on.  There's
>> 4 host bridges, 2 devices on each host bridge, and an extra CFMWS per
>> socket that is intended to interleave across the host bridges.
>>
> 
> Thanks for confirm. Honggyu represented it as a tree sturcture:
> rootport/
> ├── socket0
> │   ├── cross-host-bridge0 -> SRAT && CEDT (interleave on) --> NODE 2
> │   │   ├── host-bridge0 -> CEDT
> │   │   │   ├── cxl0 -> CEDT
> │   │   │   └── cxl1-> CEDT
> │   │   └── host-bridge1 -> CEDT
> │   │       ├── cxl2 -> CEDT
> │   │       └── cxl3 -> CEDT
> │   └── dram0 -> SRAT ---------------------------------------> NODE 0
> └── socket1
>      ├── cross-host-bridge1 -> SRAT && CEDT (interleave on)---> NODE 3
>      │   ├── host-bridge2 -> CEDT
>      │   │   ├── cxl4 -> CEDT
>      │   │   └── cxl5 -> CEDT
>      │   └── host-bridge3 -> CEDT
>      │       ├── cxl6 -> CEDT
>      │       └── cxl7 -> CEDT
>      └── dram1 -> SRAT ---------------------------------------> NODE 1

Some simple corrections here.  host-bridge{0-3} above aren't detected from CEDT.
The corrected structure is as follows.

rootport/
├── socket0
│   ├── cross-host-bridge0 -> SRAT && CEDT (interleave on) --> NODE 2
│   │   ├── host-bridge0
│   │   │   ├── cxl0 -> CEDT
│   │   │   └── cxl1-> CEDT
│   │   └── host-bridge1
│   │       ├── cxl2 -> CEDT
│   │       └── cxl3 -> CEDT
│   └── dram0 -> SRAT ---------------------------------------> NODE 0
└── socket1
      ├── cross-host-bridge1 -> SRAT && CEDT (interleave on)---> NODE 3
      │   ├── host-bridge2
      │   │   ├── cxl4 -> CEDT
      │   │   └── cxl5 -> CEDT
      │   └── host-bridge3
      │       ├── cxl6 -> CEDT
      │       └── cxl7 -> CEDT
      └── dram1 -> SRAT ---------------------------------------> NODE 1

Thanks,
Honggyu