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[67.164.59.41]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b4f8a0a2851sm12010238a12.37.2025.09.05.10.47.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Sep 2025 10:47:40 -0700 (PDT) Date: Fri, 5 Sep 2025 10:47:38 -0700 From: "Vishal Moola (Oracle)" To: David Hildenbrand Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [PATCH] mm: tag kernel stack pages Message-ID: References: <20250820202029.1909925-1-vishal.moola@gmail.com> <84297d37-b766-4cfe-9c3f-bff1cb3cb4a4@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <84297d37-b766-4cfe-9c3f-bff1cb3cb4a4@redhat.com> X-Stat-Signature: gpyi66ryoxqorjokmw8uj1zcgewwrwkk X-Rspam-User: X-Rspamd-Queue-Id: C7277A0011 X-Rspamd-Server: rspam05 X-HE-Tag: 1757094462-205589 X-HE-Meta: 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 qljrXTkT lCeYi/TMxUOZ+iF28PpYL8KmaX+V0BGBKmOI6apxVkgIlZdzbeXiKCdQIRaIfIYlX48tkzc+AgGOM/vKwtv4HcHMOTf57EvVZVGxAkonWDJ/IgpzWftRISK4FMh9QsBB0NeIDPY9CFOJYVzKJYBvos9E5FlD2lozEbbTt6i99SDD93mLLYrW8NOAmSjX7WxvXrYCFjMFYeoZ4X6HwZ8R7G8PwyCaib7P4YUmqM4vDyDepLDs/rSq84rhaPVawnHcTccSqH+oXeSSfBHa9V53ioiqvCCd1vyriEQ6gTpMjAtGvKQcslDweB/fKwAJ6YfOM7An+48UP63OPmO+Ke1jiMpwtO41YImN0cWD/z1Oo3GKyjfJrmEOCAblk/yrU6lArju88f6YQ6pkPX332q6a6HholUdUVX/DZ7KfClotWRvzN89P1tzkiFhK03AlUgcakPOcCFlQ8ivp5PnZAmJGoAnlwppvnnRiIhUVoHTFwXd/Lx7o= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Sep 04, 2025 at 12:23:31PM +0200, David Hildenbrand wrote: > 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. I agree, this shouldn't be tied to specific kernel configs. We can leave this out of tree. I didn't know a page could only have one type, and trying to handle that doesn't help explore what we're interested in right now anyway. > 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. Thanks for the suggestion, page-owner looks useful for playing around with different kernel stack allocation methods :) > -- > Cheers > > David / dhildenb >