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Peter Anvin" , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Michal Simek , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Nishanth Menon , Lucas Stach References: <20251219161559.556737-1-arnd@kernel.org> <20251219161559.556737-2-arnd@kernel.org> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: ed5gcm8etq6ns5j13cmtwtn3gjsuasa8 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 80A6A10000E X-Rspam-User: X-HE-Tag: 1766309426-527531 X-HE-Meta: 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 RRA98Dbk AqmEb+ulHYhZZixClx5NJGKdNf3giVu/vpyb9+XsCKoBVqDkepCtk0lpLaaGwsbyDhfiy1qiGUye/u7e4yYDrvsMJ9XEepm1F5zXYqDMSTfqwj86Lu+bFd8VQ3O6toiPSiIwkPFa/sQKTQ/Sjihx7o2leN8LObuuTWqNkgeX2k0oz7yM6tvHnUXWpUcFey0iAFqpHUrv+9zAR2/PAMfhUjaNKOfSX5LtCTijEwg5Kk7Ztz9cjfwY72ch7cEmLeYS0xOPp 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 12/19/25 21:52, Dave Hansen wrote: > On 12/19/25 12:20, Arnd Bergmann wrote: >>> For simplicity, I think this can just be: >>> >>> - default VMSPLIT_3G >>> + default VMSPLIT_2G >>> >>> I doubt the 2G vs. 2G_OPT matters in very many cases. If it does, folks >>> can just set it in their config manually. >>> >>> But, in the end, I don't this this matters all that much. If you think >>> having x86 be consistent with ARM, for example, is more important and >>> ARM really wants this complexity, I can live with it. >> Yes, I think we do want the default of VMSPLIT_3G_OPT for >> configs that have neither highmem nor lpae, otherwise the most >> common embedded configs go from 3072 MiB to 1792 MiB of virtual >> addressing, and that is much more likely to cause regressions >> than the 2816 MiB default. >> >> It would be nice to not need the VMSPLIT_2G default for PAE/LPAE, >> but that seems like a larger change. > > The only thing we'd "regress" would be someone who is repeatedly > starting from scratch with a defconfig and expecting defconfig to be the > same all the time. I honestly think that's highly unlikely. > > If folks are upgrading and _actually_ exposed to regressions, they've > got an existing config and won't be hit by these defaults at *all*. They > won't actually regress. > > In other words, I think we can be a lot more aggressive about defaults > than with the feature set we support. I'd much rather add complexity in > here for solving a real problem, like if we have armies of 32-bit x86 > users constantly starting new projects from scratch and using defconfigs. > > I'd _really_ like to keep the defaults as simple as possible. I agree with that. In particular in areas where there is the chance that we could count the number of people that actually care about that with one hand (in binary ;) ). -- Cheers David