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b=EGulu5ZyFyUvVdMAfBtWjFgP8rSSL0HpiletGPpKEn0Zuh8N4ftMXXFQ4mqZZiD5J IVJycgTh1khV6E9wsVdMvWeB95R18aEUav5FpKBGMmjbHkfGt3m6w9cKVbPk5blw44 UKYj8ghbMdkBaegXU4VhgUbin+dNH1COOq1cT+6C4JQuZfL1xER+hpAA7sc4pJqRIN kcb/Jlmaz9v+dQN+teZ6dvEKEkuIBU1V3nahtuELsHI15aHITRbAERcvVIPY4EoE3C SKkxZRXF5PJRba37woZvUK9GfmIvY2gnJe3DyjTQ9FtBKHY2sa96iT4GJ1dUhmH+0Q 6/A5Jt7Wz+org== Date: Thu, 9 Jul 2026 13:45:35 +0300 From: Mike Rapoport To: Muchun Song Cc: Andrew Morton , Oscar Salvador , David Hildenbrand , linux-mm@kvack.org, Vlastimil Babka , Lorenzo Stoakes , Michal Hocko , linux-kernel@vger.kernel.org, muchun.song@linux.dev Subject: Re: [PATCH 04/17] mm/mm_init: skip initializing shared vmemmap tail pages Message-ID: References: <20260702093821.2740183-1-songmuchun@bytedance.com> <20260702093821.2740183-5-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260702093821.2740183-5-songmuchun@bytedance.com> X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: A327E40006 X-Stat-Signature: 7u7yqt7xw4o33mcpeuqn4r4s4pck4kmn X-HE-Tag: 1783593943-195135 X-HE-Meta: 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 VSvl3upQ VKZ9EceOFGh1dsfR3U7cIeZk4x3hfHR7rQvjD9omu4rPdt1dZKq3Jkgvy5gtdF7IpI4uuHB3uTLVRXrQ99HyV+qY4+DYZo7YMOCTYBsD5axLJPESoIi7Pgh8UwYx2ZXylIsRYjgvGMbWOYeA3sOTV4Bm3o2uJeGJ4kfpxkn+G+eVqaL6DUuPdT4dcmvG9mYBn2Fc6r49QEEQDfXXBhFUMo7wf6RP8HD7TXjEwcH8r1N+qpG8kDIksuPGUWTLifEOOlov5h54v5GasfFO85XO2BHDF4XQaLMrgx6u7gNHV1xLFM1vbrxxxCPdJ+LlQAfnjExAW Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Muchun, Below are some preliminary comments, I'm planning to spend more time on review next week. On Thu, Jul 02, 2026 at 05:38:08PM +0800, 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, so users such as HugeTLB have to open-code > follow-up handling to restore the metadata afterwards. > > Use the section's compound page order to detect struct pages that fall > into the shared tail vmemmap range and skip their initialization in > memmap_init_range(). Still initialize the pageblock migratetypes for > the skipped range so the surrounding setup remains intact. > > 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. > > Signed-off-by: Muchun Song > --- > include/linux/mmzone.h | 4 ++++ > mm/internal.h | 16 ++++++++++++++++ > mm/mm_init.c | 25 +++++++++++++++++++------ > 3 files changed, 39 insertions(+), 6 deletions(-) > > @@ -673,19 +673,21 @@ static inline void fixup_hashdist(void) > static inline void fixup_hashdist(void) {} > #endif /* CONFIG_NUMA */ > > -#if defined(CONFIG_ZONE_DEVICE) || defined(CONFIG_DEFERRED_STRUCT_PAGE_INIT) > static __meminit void pageblock_migratetype_init_range(unsigned long pfn, > - unsigned long nr_pages, int migratetype, bool atomic) > + unsigned long nr_pages, int migratetype, bool isolate, bool atomic) What is isolate parameter for? > { > const unsigned long end = pfn + nr_pages; > > for (pfn = pageblock_align(pfn); pfn < end; pfn += pageblock_nr_pages) { > - init_pageblock_migratetype(pfn_to_page(pfn), migratetype, false); > + init_pageblock_migratetype(pfn_to_page(pfn), migratetype, isolate); > +#ifdef CONFIG_SPARSEMEM > if (!atomic && IS_ALIGNED(pfn, PAGES_PER_SECTION)) > +#else > + if (!atomic && IS_ALIGNED(pfn, MAX_FOLIO_NR_PAGES)) > +#endif Let's trigger cond_resched() on some defined number of iterations or some memory size chunk, e.g PAGES_PER_128M or even PAGES_PER_1G. > cond_resched(); > } > } -- Sincerely yours, Mike.