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Howlett" , Suren Baghdasaryan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song References: <20260825084608.47437-1-songmuchun@bytedance.com> <20260825084608.47437-4-songmuchun@bytedance.com> From: Qi Zheng In-Reply-To: <20260825084608.47437-4-songmuchun@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 66014A0004 X-Stat-Signature: o5ifr98q8xknmch3ndt31h7co1fwe68a X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1787652961-188789 X-HE-Meta: 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 EufH11yb C1oqPFceazKmU1ZN/MkyhBAwEqUZ3dah0yBq11gPtfhg8Qyn6AepQRfIxJPCeRlnspPp9A1FULVorRFaI+Xte16k17i5a9TmQMbKa4JtSlOWt1+RLa/bkXU9fo7VJ3HAK+e90QIpf1alcB7wu3T+LHKe1LY+OdKztowexd0sEdlfRb9IP0iTUkC0T/xbuoeO/N75YD/D4/1Ws6oP/wGWs7f1FjVjdArh3dNpPDm+UWha1ixJuZaExWB2eq6pbYJorq3S2MzJT/ss6JfROg4ZB3ydWlkhz8TZWNSWUtDGagcjlD6+EuVL6pUOo0bkvPpnjbvNWUiG4kKEgYGila+6pHvFXo6ggxmQ306dTbl532qC3Sjz+1wNOsThGicaXagz4vgWwMjba+6C/oC1exikIAqav/xZvOKZRqjx5b1G1MliltDk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/25/26 4:45 PM, Muchun Song wrote: > memmap_init_range() initializes every struct page in the target range. > For compound pages with vmemmap optimization, the tail struct pages are > backed by a shared vmemmap page. > > Initializing those tail struct pages would overwrite the shared > vmemmap page contents, requiring users such as HugeTLB to restore the > metadata afterwards. > > Track the compound order for HVO-backed sections and use that metadata > to detect struct pages that fall into the shared tail vmemmap range. > Skip those shared tail pages in memmap_init_range(), then initialize > pageblock migratetypes for the processed range with a helper after the > per-page initialization loop. > > Keep direct mem_section access inside sparse helpers by exposing > pfn_to_section_order() to users that only need the order associated with > a PFN. This lets memmap_init_range() skip shared tail vmemmap pages > without exposing __pfn_to_section() to !SPARSEMEM builds. > > This is a preparatory change for consolidating handling across users of > vmemmap optimization, and it also avoids redundant initialization of > shared tail vmemmap pages during early boot. That early-boot benefit > appears only once HugeTLB is switched to this common handling, since > HugeTLB is the early-boot user that creates those shared tail vmemmap > pages. > > Signed-off-by: Muchun Song Acked-by: Qi Zheng Thanks, Qi