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From: Muchun Song In-Reply-To: <1f8d0cd2-c990-4597-bf47-5a8217acc464@kernel.org> Date: Wed, 1 Apr 2026 15:28:36 +0800 Cc: Muchun Song , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Petr Tesarik , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <6B06FA9A-F332-4BE8-B80A-BB869802600F@linux.dev> References: <20260331113023.2068075-1-songmuchun@bytedance.com> <32789381-f860-4b60-a1e1-4c97f6ed08b1@kernel.org> <7C90E910-D229-4F60-A62D-E893A89D58F2@linux.dev> <1742503A-F912-4AB6-AAF6-6CDB06829024@linux.dev> <9fddd112-e304-4ce1-b3f0-a4b133fcb281@kernel.org> <1f8d0cd2-c990-4597-bf47-5a8217acc464@kernel.org> To: "David Hildenbrand (Arm)" X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 85DA3A0008 X-Stat-Signature: 3gcy4c144xqyfypn4akego459ojyix6o X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1775028552-632824 X-HE-Meta: U2FsdGVkX1/9fRJs5pA7FcE6s/+bS3fedX06oY2ZDqjuvxlHtk4G6c4TQ6NE/CW6egNrvAFv8EgdbxH+yctzRajCPAOvVh7bMf04HYfX0iXQqY+pQkBs5slQo1/gCOC9/JqgZGQTfTzIY3qdQUYZMeeQCd6WXcseJ1t7Jwc41Ke6IaYmgHE7a5eC0Bm7cvGhXzo8KAjbiP2untXRKbIVs+HHc1MOC6wmMA3wJyWdpcnr7Z5OFg9jhiEoOSEsJ2BUPK5oD2/dCU68aX6SPa66yyRuAfztkReQ8lU00dSXE9Z5Vq6KVkXf/JLoh7L6Feif1QRIIkBzfaS+ptviktTzttOCpSA19Re3LwJ8/c8vkgiFzRKr2Pf9Hzm2w+2H5TP2enlYk37bwUfws4x020B1eTJotm3NnMXSazULHGC+FIALQkl0/tJVDWgsJiZPraFl5KTSn0Q4hm+rQkbSQ9casWWIzTLO9hP3x5SiBC2M1RIIfzYHWmA/d9xaXI8CrTpeft2+sIouwXMGxK7XtiR07mUJl/LPUDgqXNexgGfMxUsbyQ+vdU9dZ2O1Bjnzjv4S7BIGr0nj/bVDlhCV1DPEs+A5LbtTT03ivjMkq/vw5tdCmFXqAoFuc/nToaRRBk5CsHP6Fzi6BU9CVtlrFsnvYYkxzU/0J0O0Exm/gfxk+xZCFy9LCoLLLkhlWWlZhDsWEN/FntsNK60PVBLOwPtO1bQppHUC0SCMAV63xTdcB6OUrVIDbu77WdujKzPQFmPXnbqHeCUEu0cXS2726c1zzmSswAy6JoAVfxMuHH+mcNed7Ux1hBTR5kO/QA3Som5kTOxajEe01RYxCG+CLz8ZI/twZUwr47XENenvDz7kiUCSh27tAj3IbUMQErnFqEj33ITz4FB4E9kQy59L3MmhDpeagNgU285YW8cdRuRavKzAtB6emLb6vA6EoHWLeA6ctrC8IqCBjotpEW7IBGr HykaDu8g AOpTvWLCaPKkSrKuDDuRYJoE2OOAqoHOkZwOLdCUhmIiLvQBLiwex61Ri/iO/+pgDFCDrOw3Fx7vWeUPZj3wPeqUP6aTW/U/GOnjFNynYlB+AMEGSmwiBb002v0a2XLRxQcCcDTBAObzstpECKtqx0p2m4VjUZF03vR3HRrGiytdnLOQFLka0VJVOF8nNa9PvD8X1Hb3yz8d30wdYK2hsWYN0aoPXGPP+/fmSfqdvpc4oRey80U1+UvVUxH5nGlfHfB79CEF8OL/CI6MSecJW1GfXDrvSBR4Ot0oKYP6z4Z7uPKhyv03sM03yyw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Apr 1, 2026, at 15:26, David Hildenbrand (Arm) = wrote: >=20 > On 4/1/26 09:23, Muchun Song wrote: >>=20 >>=20 >>> On Apr 1, 2026, at 15:08, David Hildenbrand (Arm) = wrote: >>>=20 >>> On 4/1/26 06:01, Muchun Song wrote: >>>>=20 >>>>=20 >>>>=20 >>>> Sorry, I misread it earlier =E2=80=94 I thought it was about the = memory >>>> section size, but it's actually about the memmap size. Let me = respond >>>> again to your question. On the powerpc architecture, when = PFN_SECTION_SHIFT >>>> is 6 and PAGE_SHIFT is 18, it does seem that the memmap of a memory >>>> section would be smaller than a single page. >>>=20 >>> Right, and I am saying we don't care about that and do not support = it. >>>=20 >>> For example, most vmemmap code I am aware of relies on a single = section >>> covering full pages. >>>=20 >>> So I don't think this patch here adds any value, except faking that = we >>> might be supporting something we don't? >>=20 >> Got it. >>=20 >> My original motivation was simply that when I read this part of the = code, >> the comment felt a bit off to me, so I just fixed it casually. But if = it >> ends up creating the impression that "we might be supporting = something >> we don't," as you said, then I'm fine with dropping this patch. >=20 > Can you rework your patch to only simplify the comment, and to clarify > that we always expect a single section to cover full pages? No problem. >=20 > --=20 > Cheers, >=20 > David