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

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Message-ID: <20250311020806.404-1-yunjeong.mun@sk.com>
Date: Tue, 11 Mar 2025 11:07:27 +0900
From: Yunjeong Mun <yunjeong.mun@...com>
To: 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,
	yunjeong.mun@...com,
	Honggyu Kim <honggyu.kim@...com>
Subject: Re: [PATCH 2/2 v6] mm/mempolicy: Don't create weight sysfs for memoryless nodes

Hi Gregory,

On Mon, 10 Mar 2025 10:22:11 -0400 Gregory Price <gourry@...rry.net> wrote:
> On Mon, Mar 10, 2025 at 09:26:48PM +0900, Honggyu Kim wrote:
> > Yeah, the proximity domain detects the node correctly as follows in dmesg.
> > 
> >  [  0.009915] ACPI: SRAT: Node 0 PXM 0 [mem 0x00000000-0x7fffffff]
> >  [  0.009917] ACPI: SRAT: Node 0 PXM 0 [mem 0x100000000-0x207fffffff]
> >  [  0.009919] ACPI: SRAT: Node 1 PXM 1 [mem 0x60f80000000-0x64f7fffffff]
> >  [  0.009924] ACPI: SRAT: Node 2 PXM 6 [mem 0x2080000000-0x807fffffff] hotplug
> >  [  0.009925] ACPI: SRAT: Node 3 PXM 7 [mem 0x64f80000000-0x6cf7fffffff] hotplug
> > 
> > It is printed even before CXL detection.
> > 
> 
> I wrote a some documentation on some example configurations last friday
> 
> https://lore.kernel.org/linux-mm/Z226PG9t-Ih7fJDL@gourry-fedora-PF4VCD3F/T/#m2780e47df7f0962a79182502afc99843bb046205
> 

I've checked our CFMWS configurations using the information from this link and 
wrote them below.

> This isn't exhaustive, but as I said with Rakie, I think your
> configuration is probably ok - if slightly confusing.
> 

I wonder if the below data is sufficient for your review in Rakies's
email [1]. Please let me know.

> What I'm going to guess is happening is you have 1 CFMWS per device that
> do not have matching SRAT entries, and then the CFMWS covering these:
> 
> >  [  0.009924] ACPI: SRAT: Node 2 PXM 6 [mem 0x2080000000-0x807fffffff] hotplug
> >  [  0.009925] ACPI: SRAT: Node 3 PXM 7 [mem 0x64f80000000-0x6cf7fffffff] hotplug
> 
> have interleave set up
> 

In my understanding, both SRAT and CFMWS have the above device and interleave setup.

Below are the SRAT entries (with some unnecessary lines removed) :

[A128h 41256 001h]               Subtable Type : 01 [Memory Affinity]  
[A12Ah 41258 004h]            Proximity Domain : 00000006  
[A130h 41264 008h]                Base Address : 0000002080000000
[A138h 41272 008h]              Address Length : 0000006000000000  
                                     Enabled : 1  
                               Hot Pluggable : 1  
...
  
[A150h 41296 001h]               Subtable Type : 01 [Memory Affinity]  
[A152h 41298 004h]            Proximity Domain : 00000007  
[A158h 41304 008h]                Base Address : 0000064F80000000
[A160h 41312 008h]              Address Length : 0000008000000000  
                                     Enabled : 1  
                               Hot Pluggable : 1  

and below are the CFMWS configurations (with some unnecessary lines removed):

[0A4h 0164 001h]               Subtable Type : 01 [CXL Fixed Memory Window Structure]
[0ACh 0172 008h]         Window base address : 0000002080000000 <- Memory region
[0B4h 0180 008h]                 Window size : 0000032780000000
[0BCh 0188 001h]          Interleave Members : 01           <-- 2-way interleave
[0BDh 0189 001h]       Interleave Arithmetic : 01
[0C8h 0200 004h]                First Target : 00000043     <-- host bridge id  
[0CCh 0204 004h]                 Next Target : 00000053     <-- host bridge id 

...

[170h 0368 001h]               Subtable Type : 01 [CXL Fixed Memory Window Structure]
[178h 0376 008h]         Window base address : 0000064F80000000
[180h 0384 008h]                 Window size : 0000033000000000
[188h 0392 001h]          Interleave Members : 01          <-- 2-way interleave
[189h 0393 001h]       Interleave Arithmetic : 01
[194h 0404 004h]                First Target : 00000143    <-- host bridge id
[198h 0408 004h]                 Next Target : 00000153    <-- host bridge id

[1] https://lore.kernel.org/linux-mm/Z87zpg3TLRReikgu@gourry-fedora-PF4VCD3F/

Best regards,
Yunjeong