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b=G3o6lrkAn+/fVkI251MMo8MMjUTiQr9KTPberfX7b0Br8mtHbr0hsxJghBWOYpxzB +7GjrVCZv0SN0cykNtvyMpbnaAILWKNHk2DmSA6MtVG1l00+baBmKtU0X7vcNN68M2 tBEjhf0fORijaqupTeEtKY65t8CQHCCXR+h7H4wTOzxMosTVCU7tThyRLGzcgzriBq iFm90dyyU8L+45ZZi7rnQHAWcju9B/roRv1S8QDc5wUX0GBziulSNKBR0RAp/JGfyO +aMG6Vrfgvq/RmZyobjirgFQoieySCu6LwVWFjei/uzYpyGVInOU8lpArnAJJBeN5C Ls64ou6GY7GeQ== Date: Tue, 2 Jun 2026 20:31:42 +0300 From: Mike Rapoport To: "Vlastimil Babka (SUSE)" Cc: "David Hildenbrand (Arm)" , Lorenzo Stoakes , Nico Pache , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, liam@infradead.org, mhocko@suse.com, vbabka@suse.cz, willy@infradead.org Subject: Re: Process (was Re: [PATCH mm-hotfixes-unstable v18 00/14] khugepaged: add mTHP) collapse support Message-ID: References: <506fed6b-8954-40fa-8b5e-c8bd8c0d004b@kernel.org> <07334dc3-79ba-407e-96be-21ceb2eec00a@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <07334dc3-79ba-407e-96be-21ceb2eec00a@kernel.org> X-Rspamd-Server: rspam07 X-Rspam-User: X-Stat-Signature: xcsn8xwjeb8cyzckbscbodu7gigsjwac X-Rspamd-Queue-Id: 8394D40016 X-HE-Tag: 1780421510-873742 X-HE-Meta: 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 wK6PplwT CLSZ3KJPefwzan6c+9MCuSWJ0ZcIypZZ6tTMaPW0LTh3Mw1BZDg5tLkIryJuVtNfF5p2QbRtXZ03Ggkv/HzF1MM1hDfseqbZx3SPpD49Q9ll7TeOKtWjjMxNCba9UY444yyKv/fH3/ERuKFmNRj0F9MqnhMUR/iZI6kqJ/hrElPzFHuODow60i7ql9loWL1hfFTlolSWWweWf4NBXa+e3YyZSDwt+Sg5Zm7XWbKjhhQnLv9U/gUiNiRg6BHzcpBQUHP8Mp6tn10QbmXdADsT8dAnFDw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jun 02, 2026 at 02:55:30PM +0200, Vlastimil Babka (SUSE) wrote: > On 6/2/26 13:31, David Hildenbrand (Arm) wrote: > >>> learn from obviously) against how mm works in practice. > >>> > >>> High review load with many overlapping changes might favour a different approach > >>> to a subsystem that looks different from that. > >> Yeah, but as we said, we discussed, it's all rather complicated and we should > >> move incrementally. > >> > > > > Starting to read Documentation/process/maintainer-tip.rst, it's very interesting: > > > > “The tip tree is both a direct development tree and and an aggregation tree for > > several sub-maintainer trees.” > > > > “In general, development against the head of the tip tree master branch is fine, > > I don't think we'll be able to use this part as mm-next will be only an > aggreggation tree and not also a direct development tree. > > > but for the subsystems which are maintained separately, have their own git tree > > and are only aggregated into the tip tree, development should take place against > > the relevant subsystem tree or branch.” > > So it would have to be this. > As it might be hard for contributors to pick the right one (as Lorenzo > pointed out), we might in general suggest they try developing against rc1 > first (which is the common base of all subsystem trees), then either it > applies to one of the subsystem trees as-is, or it applies as a topic branch > (which starts also on the rc1 base) with reasonable conflict resolution > during merge, or we tell them which exising subtree/branch to rebase on. Unless we carry semi-baked work through merge window *, at rc1 all trees anyway restart the cycle. So basing new work on rc1 is very reasonable choice. Once that work is merged it will be merged to a particular sub-tree. Even patchsets that touch files across the trees still will be merged to a single sub-tree. And once a patches is merged it's clear what should be the base for the work that builds on top of that patchest. Obviously there would be conflicts when sub-trees are merged into the integration tree, but that's maintainers responsibility to resolve them IMHO. * Supposing we keep the model of early merging for testing [Lorenzo, don't yell at me ;-)] I think it's reasonable enough to drop everything that's not going upstream at, say, rc6 and ask contributors to rinse and repeat after rc1. > > “Bug fixes which target mainline should always be applicable against the > > mainline kernel tree. Potential conflicts against changes which are already > > queued in the tip tree are handled by the maintainers.” > > Ack. +1 -- Sincerely yours, Mike.