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From: Muchun Song In-Reply-To: <20260804035535.2846016-6-songmuchun@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: EC13F1A0003 X-Stat-Signature: w3p9561ebccycfznw3tr1z1om6mu453k X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1786419963-305248 X-HE-Meta: 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 x0nHbDw1 +xF9jFq6zbLL9L0r8btmOT96fNDIWAB0R7PYK8yhjcKtYPc60Xc1OhG5xI9hVupB/rnjqun6BkFHFUsP0CtfwEjym7/JJ7YKWmsHDwmX6rz3oL3alJPjzdenWO2PeBqfRf5NlrZUGdPwWcoy86rFM/rO/U4ohk6LY/FG0JdE9kfyLMa6Ovrv0opofdY6jhDoAGwdUHKrMDAxm++3aQxB5L98yTl+zWvPLEkUMYzWB6140LWvJWUa5GjeXq800SILhU3TtNljRQKACiwWHq8WslXbiL5I2I8Z0JsKeXghkjwoiGM+8TTe2Af1UZg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026/8/4 11:55, Muchun Song wrote: > section_nr_vmemmap_pages() can account ordinary sections and DAX sections, > but section-based vmemmap optimization keeps its compound order in struct > mem_section and retains a different number of vmemmap pages. > > Teach section_nr_vmemmap_pages() to recognize section-based optimized > sections and calculate their vmemmap page count from the section order > and the HVO retained page count. > > Signed-off-by: Muchun Song > --- > v3: > - Add vmemmap_optimizable_order() for order-based optimization checks > > v2: > - Remove an unnecessary vmemmap_can_optimize() call to simplify the code > (suggested by Mike Rapoport). > - Rewrite the commit message for better understanding. > --- > include/linux/mmzone.h | 6 ++++-- > mm/sparse-vmemmap.c | 10 ++++++---- > mm/sparse.h | 16 ++++++++++++++++ > 3 files changed, 26 insertions(+), 6 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 81e16d71e1f0..663726dd6463 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -107,8 +107,10 @@ > is_power_of_2(sizeof(struct page)) ? \ > MAX_FOLIO_NR_PAGES * sizeof(struct page) : 0) > > -/* The number of struct pages covered by the retained vmemmap pages with HVO enabled. */ > -#define VMEMMAP_OPTIMIZATION_NR_STRUCT_PAGES (PAGE_SIZE / sizeof(struct page)) > +/* The number of retained vmemmap pages with HVO enabled. */ > +#define VMEMMAP_OPTIMIZATION_PAGES 1 > +#define VMEMMAP_OPTIMIZATION_NR_STRUCT_PAGES \ > + (VMEMMAP_OPTIMIZATION_PAGES * PAGE_SIZE / sizeof(struct page)) > #define VMEMMAP_OPTIMIZATION_MIN_ORDER (ilog2(VMEMMAP_OPTIMIZATION_NR_STRUCT_PAGES) + 1) > > #define __VMEMMAP_OPTIMIZATION_NR_ORDERS \ > diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c > index 107215cf8488..b7abc5494bb9 100644 > --- a/mm/sparse-vmemmap.c > +++ b/mm/sparse-vmemmap.c > @@ -649,24 +649,26 @@ void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn) > static int __meminit section_nr_vmemmap_pages(unsigned long pfn, unsigned long nr_pages, > struct vmem_altmap *altmap, struct dev_pagemap *pgmap) > { > - const unsigned int order = pgmap ? pgmap->vmemmap_shift : 0; > + const struct mem_section *ms = __pfn_to_section(pfn); > + const int order = pgmap ? pgmap->vmemmap_shift : section_order(ms); > + const int vmemmap_pages = pgmap ? VMEMMAP_RESERVE_NR : VMEMMAP_OPTIMIZATION_PAGES; > const unsigned long pages_per_compound = 1UL << order; > > VM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, PAGES_PER_SUBSECTION)); > VM_WARN_ON_ONCE(nr_pages > PAGES_PER_SECTION); > > - if (!vmemmap_can_optimize(altmap, pgmap)) > + if (!vmemmap_can_optimize(altmap, pgmap) && !section_vmemmap_optimizable(ms)) > return DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE); Sashiko said this conditional logic mix DAX and HVO optimization checks in a way that severely corrupts vmemmap accounting for nr_memmap_pages. This is a false positive because its premise is based on memory hotplug support for HVO. However, HVO cannot be enabled through memory hotplug at this time. Muchun, Thanks. > > if (order < PFN_SECTION_SHIFT) { > VM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, pages_per_compound)); > - return VMEMMAP_RESERVE_NR * nr_pages / pages_per_compound; > + return vmemmap_pages * nr_pages / pages_per_compound; > } > > VM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION)); > > if (IS_ALIGNED(pfn, pages_per_compound)) > - return VMEMMAP_RESERVE_NR; > + return vmemmap_pages; > > return 0; > } > diff --git a/mm/sparse.h b/mm/sparse.h > index b9b6b47e85ce..6ad190ec48cf 100644 > --- a/mm/sparse.h > +++ b/mm/sparse.h > @@ -43,6 +43,17 @@ static inline bool pfn_vmemmap_optimizable(unsigned long pfn) > return (pfn & (nr_pages - 1)) >= VMEMMAP_OPTIMIZATION_NR_STRUCT_PAGES; > } > > +static inline bool vmemmap_optimizable_order(unsigned int order) > +{ > + if (!IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP)) > + return false; > + > + if (!is_power_of_2(sizeof(struct page))) > + return false; > + > + return order >= VMEMMAP_OPTIMIZATION_MIN_ORDER; > +} > + > /* > * mm/sparse.c > */ > @@ -80,6 +91,11 @@ static inline void __section_mark_present(struct mem_section *ms, > > ms->section_mem_map |= SECTION_MARKED_PRESENT; > } > + > +static inline bool section_vmemmap_optimizable(const struct mem_section *section) > +{ > + return vmemmap_optimizable_order(section_order(section)); > +} > #else > static inline void sparse_init(void) {} > #endif /* CONFIG_SPARSEMEM */