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Thu, 20 Aug 2026 07:11:16 -0400 (EDT) Date: Thu, 20 Aug 2026 12:11:15 +0100 From: Kiryl Shutsemau To: "David Hildenbrand (Arm)" Cc: akpm@linux-foundation.org, ljs@kernel.org, nico.pache@linux.dev, baolin.wang@linux.alibaba.com, baohua@kernel.org, dev.jain@arm.com, hughd@google.com, lance.yang@linux.dev, liam@infradead.org, mhocko@suse.com, rppt@kernel.org, ryan.roberts@arm.com, shuah@kernel.org, surenb@google.com, usama.arif@linux.dev, vbabka@kernel.org, ziy@nvidia.com, usama.anjum@arm.com, agordeev@linux.ibm.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, jannh@google.com, willy@infradead.org, pfalcato@suse.de, rostedt@goodmis.org, mhiramat@kernel.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [RFC PATCH 03/57] mm/collapse: add collapse.h for the shared collapse state Message-ID: References: <20260816224609.308019-1-kirill@shutemov.name> <20260816224609.308019-4-kirill@shutemov.name> <3113ac8b-c1ce-4577-9e93-449b70818918@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3113ac8b-c1ce-4577-9e93-449b70818918@kernel.org> On Wed, Aug 19, 2026 at 04:19:41PM +0200, David Hildenbrand (Arm) wrote: > On 8/17/26 00:45, Kiryl Shutsemau wrote: > > From: "Kiryl Shutsemau (Meta)" > > > > Preparation for building the new collapse engine in its own file. The > > engine and khugepaged.c need to agree on what a collapse result is and > > what state a scan carries. > > > > Move enum scan_result and struct collapse_control into a new > > mm/collapse.h. > > > > No functional change intended. > > > > Assisted-by: Claude-Code:claude-opus-5 > > Signed-off-by: Kiryl Shutsemau (Meta) > > --- > > BTW, I'm wondering whether it would result in less churn (independent of the > other changes) to > > a) Rename mm/khugeapged.c to mm/collapse.c > > b) Move stuff into mm/collapse.h that a new ... > > c) mm/khugapegd.c will need. I went for a clean collapse.c on purpose: the engine is new code, and a new file keeps it readable while both mechanisms are in the tree, with 28 as a plain delete from khugepaged.c. Your shape is less churn, though, and it keeps blame: 29-35 move about 1700 lines as add-and-delete today, and most of that would stay put, with only the daemon -- mm_slot, the scan loop, sysfs -- extracted into a new khugepaged.c. If you prefer it that way, I can give it a try for v2. The rename has to open the series, so it will collide with anything in flight that touches khugepaged.c. -- Kiryl Shutsemau / Kirill A. Shutemov