linux-kernel - Re: [PATCH] mm: tag kernel stack pages

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Message-ID: <84297d37-b766-4cfe-9c3f-bff1cb3cb4a4@redhat.com>
Date: Thu, 4 Sep 2025 12:23:31 +0200
From: David Hildenbrand <david@...hat.com>
To: "Vishal Moola (Oracle)" <vishal.moola@...il.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mm: tag kernel stack pages

On 03.09.25 20:19, Vishal Moola (Oracle) wrote:
> On Wed, Sep 03, 2025 at 09:49:06AM +0200, David Hildenbrand wrote:
>> [resending my original mail because it might have landed in the spam folder]
> 
> Ah, indeed the original mail was found in my spam folder. Thanks for
> resending.
> 
>> On 20.08.25 22:20, Vishal Moola (Oracle) wrote:
>>> Currently, we have no way to distinguish a kernel stack page from an
>>> unidentified page. Being able to track this information can be
>>> beneficial for optimizing kernel memory usage (i.e. analyzing
>>> fragmentation, location etc.). Knowing a page is being used for a kernel
>>> stack gives us more insight about pages that are certainly immovable and
>>> important to kernel functionality.
>>
>> It's a very niche use case. Anything that's not clearly a folio or a
>> special movable_ops page is certainly immovable. So we can identify
>> pretty reliable what's movable and what's not.
>>
>> Happy to learn how you would want to use that knowledge to reduce
>> fragmentation. 🙂
>>
>> So this reads a bit hand-wavy.
> 
> My thoughts align with Matthew's response. If we decide "This doesn't add
> enough value to merge it upstream" thats fine by me.
> 
> Otherwise if we think this is useful, I can respin this with your
> suggestion below.

As raised in my other mail, I assume there is no way to just have any 
stack pages in any kernel config marked appropriately (slab allocation 
discussion)?

If so, I prefer to not add it.

If there is a way to just make it consistent, then no strong opinion 
from my side. Willy is the page-type guard :)

BTW, I was wondering if page-owner could be useful instead.

-- 
Cheers

David / dhildenb