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Tue, 16 Sep 2025 12:27:11 -0700 (PDT) Received: from [2a00:79e0:2eb0:8:3226:ed0a:4c73:99d2] ([2a00:79e0:2eb0:8:3226:ed0a:4c73:99d2]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-77607b346dasm17161924b3a.68.2025.09.16.12.27.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Sep 2025 12:27:09 -0700 (PDT) Date: Tue, 16 Sep 2025 12:27:08 -0700 (PDT) From: David Rientjes To: Shakeel Butt cc: Eugen Hristev , Matthew Wilcox , Amit Shah , Andrew Morton , Aneesh Kumar , Christoph Lameter , Dave Hansen , David Hildenbrand , Davidlohr Bueso , Hugh Dickins , Johannes Weiner , John Hubbard , Kirill Shutemov , Mel Gorman , Michal Hocko , Mike Rapoport , Peter Xu , Raghavendra K T , "Rao, Bharata Bhasker" , Rik van Riel , Roman Gushchin , Shivank Garg , Sterling Alexander , Suren Baghdasaryan , Tejun Heo , Vlastimil Babka , Yang Shi , Zi Yan , linux-mm@kvack.org, rdunlap@infradead.org Subject: Re: [Invitation] Linux MM Alignment Session on kmemdump on Wednesday In-Reply-To: Message-ID: <08c0b550-0a78-0b25-308d-18b143999599@google.com> References: <426751f4-428b-ed01-509b-d13e719a2006@google.com> <50b566d6-aeda-48cc-bd67-362cb29b214a@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspamd-Queue-Id: C03B94000B X-Stat-Signature: pssqw5hmune1u7qodky1xkz5s4jtss8x X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1758050832-736244 X-HE-Meta: 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 bUVzjJzA 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 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 Tue, 16 Sep 2025, Shakeel Butt wrote: > > >>>> This week's topic will be kmemdump led by Eugen Hristev. See the latest > > >>>> proposal at https://lwn.net/Articles/1031319/. > > >>> > > >>> I don't understand what this has to do with mm, to be honest. > > >>> It looks like a debugging aid. > > >> > > >> It was suggested to move it to mm/ : > > >> > > >> https://lore.kernel.org/all/0fa9e4e7-1247-4c82-8c0b-fa65b7fbb56d@infradead.org/ > > > > > > I feel like you should be able to explain this rather better than > > > "somebody else told me to move it". As of this moment, I still don't > > > know what kmemdump even is. > > > > > >>> > > >>> https://lore.kernel.org/lkml/20250422113156.575971-2-eugen.hristev@linaro.org/ > > >>> > > >>> is a great example of how to write a lot of documentation that doesn't > > >>> actually tell the reader what anything is. > > >>> > > >>> > > >> > > >> Here is a link to the v3 where I changed it a little bit : > > >> > > >> https://lore.kernel.org/all/20250912150855.2901211-1-eugen.hristev@linaro.org/ > > >> > > >> I am eager to improve the documentation to make more sense out of it, I > > >> am happy with suggestions. > > > > > > Start by telling me what it is. > > > > A way to select memory areas from the kernel that can be used to debug > > the kernel, instead of saving the whole memory dump which is mostly not > > of interest and takes a lot of space. > > Anyone can register a pointer and a size, these are placed into a list, > > and a dedicated firmware can parse it and save it in case of a crash. > > Does this make sense ? > > Is it only for kernel or is available for userspace as well? And the > crashes here, we are talking about kernel crashes or includes process > crashes as well? > Yeah, I think understanding the scope of this work, both in the current RFC as well as the long term vision, is going to be useful. In this case of kmemdump, which I agree is not core mm, it's likely best to use this alignment session to first describe the problem statement: what are we trying to solve? The reference to dedicated firmware above piques at least my curiosity. I see some interaction on the latest RFC, asking questions, and deciding the interaction with pstore, I think the goal of this session would be to determine if (1) the problem is worth solving, (2) if there are existing mechanisms that can already get us there, and (3) if the current approach makes sense long term or if any pivots are needed. Hopefully an interactive discussion will save time in the long term by ensuring alignment in this area even if the feedback turns out to be "no, we're not doing this." That would likely best be done by first describing, thoroughly, the problem statement before jumping into implementation specifics.