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Tue, 29 Sep 2026 08:44:32 +0000 X-Mizu-Trace-ID: 199085bad9bec430 X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3901.100.1.1.11\)) Subject: Re: [PATCH v5 08/12] mm/sparse-vmemmap: move vmemmap optimization helpers to a public header From: Muchun Song In-Reply-To: Date: Tue, 29 Sep 2026 16:44:12 +0800 Cc: Muchun Song , Andrew Morton , Oscar Salvador , Madhavan Srinivasan , Michael Ellerman , Jonathan Corbet , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-doc@vger.kernel.org, Lorenzo Stoakes , Mike Rapoport , Qi Zheng , Nicholas Piggin , Christophe Leroy , Randy Dunlap , Lance Yang Content-Transfer-Encoding: quoted-printable Message-Id: <0481F7BE-F912-4E83-80F1-6E7990B447C1@linux.dev> References: <20260927025441.741633-1-songmuchun@bytedance.com> <20260927025441.741633-9-songmuchun@bytedance.com> To: "David Hildenbrand (Arm)" X-Mailer: Apple Mail (2.3901.100.1.1.11) X-Stat-Signature: fzuwe55rfhxuko6bquybfh69af878n7i X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: B2CD914000A X-HE-Tag: 1790671477-90816 X-HE-Meta: U2FsdGVkX18GLtltuI7QLOYGtn9pfeSsdGAUl7EAa4YYTuPRYbLWV72MNkoR9hMSLoEE1bNE4sbb2w5xkSEg5KCuWoOeEHNMkvjGu5gAAqw3rw3CRK9+5BcHnGtUoJI+1L5ui924VtQugCoJ/B5GYnAZ2DHLbilNMzzTmBp9CEPIJPNGT1U9WyO9NEsu3VJPMUGMmyf8MCGgmzS4h7MFkN3GoFsLOpnhj6n2fXupeUOtIDLC0uJsIDdCxMIFMK8XreMibQJLXAs5Zr3y10647l8Hy3NZio7CKi9xvBShDVaC6sZND9+oD5ZZioNkBYdntkLzVZ5I1eJZjdFNf8+LqJgW0JKbAFvUlMF/N6HZ5RmeNiuB8VCUcV7cjViyhmJVPm8mQL5dIG/I42Nj4SzrKepp4qf65Gmi2BHWLR/LABsBGDl489T9n/8wsC9FPnX6BNUNUp/dNGBBwbVYb30D40kAZKA0OeyK2WYGlmNATHbxDdkUxuXUmtWBIDcBXd1HLg6min+Z6xHr+wf47luxLFBij8ytBmS1quoa40OYEzXmV+0Uoi3tfm5Gj+bDTeDHS+lhidyZ3dFApcX8sZqEjhxzR5xbjStXQpKyScQROpDLnSulj+E9528TcuNixCnPR4n4aZ80SdTcbXbtD+zd5xY+xbQJpThbW9DrGCjpQ2J4Hjr1vTUioKf4aRgfDGUjKKG221KHWEXfQT9Iks3sUQ9MHsqZ2mA0vGkacxG9i+N1SXxlyoAY7BDalI1r3xnOCDd+ByFctGmFluf/Fe0FrMsL5Dxcb8qMMagcMDIeRs+m5jGkI81JQ6GUS9YaR6MFGtLQwfb9l3dH/hAoPOW6E3ivBSB15GIUI+F4yOIyRCBh50wF99xqU0jFU5YTdBWXmnNmXJhroqCkjLgeqh71WSvnziiZxem5UyK/x6T5Eh5L+u8Fzkxy3mZk4a+KBAA/I183F4T3+3wPTcJmpW6 ivran7hc Y5SFUOpd0Ih3neNHLlObuM2v39hcIjmkkilt6Cv/DrRP5nYeb7FGwWQYsXykRaPhGlxmNaYtD4M6yTVBXW3VFw/VsOKtpZd2p5RCYQzp2EdwCybrAybQ0GDiXdq3nDYqRrumxZf+2IfeLk7o/ZHe6Oqoxuf9N6nPSYkRqr8oGZuu5ZhiqOZ+Piu1fdZnE2kSFgvQN/J/hecDMUYm1IUShv9GyR6B90DSKXIURs+5XROIttIEQ45zX7ZZlVPYr28xpTgB9o3PvWd/CDFdT+DCJgL6c6fjoKel87tSQ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Sep 29, 2026, at 15:39, David Hildenbrand (Arm) = wrote: >=20 > On 9/27/26 04:54, Muchun Song wrote: >> The vmemmap optimization helpers currently live in mm/sparse.h, >> which is an internal MM header. That works for MM code, but >> prevents powerpc from using the same interfaces without including a >> private header. >>=20 >> Move the declarations and inline helpers to vmemmap-optimization.h. >> This is a preparatory change for powerpc, which has its own vmemmap >> optimization implementation and needs to use the common vmemmap >> optimization interfaces from architecture code. >=20 > Which raises the question why powerpc was special and will remain = special. Wha's > the big problem here that powerpc must do special things? Good question. I also don't think PowerPC needs special handling, but when HVO logic was introduced for PowerPC, it handled HVO on its own. =46rom my preliminary analysis, the reason it didn't reuse the generic logic initially may be related to the fact that PowerPC's section size is 16M. With a 64k base page, a single page can cover the vmemmap range of multiple sections, and the current generic logic doesn't cover this case. However, completely removing PowerPC's special handling is already in my follow-up plan. We need to wait for the current series to enter the mainline, and then we can proceed gradually. >=20 > Change itself looks good. >=20 > Acked-by: David Hildenbrand (Arm) Thanks for your review. Muchun, Thanks >=20 > --=20 > Cheers, >=20 > David