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However, someone wants to make memory_hotplug.memmap_on_memory takes precedence over hugetlb_free_vmemmap since memmap_on_memory makes it more likely to succeed memory hotplug in close-to-OOM situations. So the decision of making hugetlb_free_vmemmap take precedence is not wise and elegant. The proper approach is to have hugetlb_vmemmap.c do the check whether the section which the HugeTLB pages belong to can be optimized. If the section's vmemmap pages are allocated from the added memory block itself, hugetlb_free_vmemmap should refuse to optimize the vmemmap, otherwise, do the optimization. Then both kernel parameters are compatible. So this patch introduces SECTION_CANNOT_OPTIMIZE_VMEMMAP to indicate whether the section could be optimized. Signed-off-by: Muchun Song --- Documentation/admin-guide/kernel-parameters.txt | 22 +++++++++---------- Documentation/admin-guide/sysctl/vm.rst | 5 ++--- include/linux/memory_hotplug.h | 9 -------- include/linux/mmzone.h | 17 +++++++++++++++ mm/hugetlb_vmemmap.c | 28 ++++++++++++++++++------- mm/memory_hotplug.c | 22 +++++++------------ mm/sparse.c | 8 +++++++ 7 files changed, 66 insertions(+), 45 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index c087f578d9d8..5359ffb04a84 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1730,9 +1730,11 @@ Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y, the default is on. - This is not compatible with memory_hotplug.memmap_on_memory. - If both parameters are enabled, hugetlb_free_vmemmap takes - precedence over memory_hotplug.memmap_on_memory. + Note that the vmemmap pages may be allocated from the added + memory block itself when memory_hotplug.memmap_on_memory is + enabled, those vmemmap pages cannot be optimized even if this + feature is enabled. Other vmemmap pages not allocated from + the added memory block itself do not be affected. hung_task_panic= [KNL] Should the hung task detector generate panics. @@ -3077,10 +3079,12 @@ [KNL,X86,ARM] Boolean flag to enable this feature. Format: {on | off (default)} When enabled, runtime hotplugged memory will - allocate its internal metadata (struct pages) - from the hotadded memory which will allow to - hotadd a lot of memory without requiring - additional memory to do so. + allocate its internal metadata (struct pages, + those vmemmap pages cannot be optimized even + if hugetlb_free_vmemmap is enabled) from the + hotadded memory which will allow to hotadd a + lot of memory without requiring additional + memory to do so. This feature is disabled by default because it has some implication on large (e.g. GB) allocations in some configurations (e.g. small @@ -3090,10 +3094,6 @@ Note that even when enabled, there are a few cases where the feature is not effective. - This is not compatible with hugetlb_free_vmemmap. If - both parameters are enabled, hugetlb_free_vmemmap takes - precedence over memory_hotplug.memmap_on_memory. - memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest Format: default : 0 diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst index 5c9aa171a0d3..d7374a1e8ac9 100644 --- a/Documentation/admin-guide/sysctl/vm.rst +++ b/Documentation/admin-guide/sysctl/vm.rst @@ -565,9 +565,8 @@ See Documentation/admin-guide/mm/hugetlbpage.rst hugetlb_optimize_vmemmap ======================== -This knob is not available when memory_hotplug.memmap_on_memory (kernel parameter) -is configured or the size of 'struct page' (a structure defined in -include/linux/mm_types.h) is not power of two (an unusual system config could +This knob is not available when the size of 'struct page' (a structure defined +in include/linux/mm_types.h) is not power of two (an unusual system config could result in this). Enable (set to 1) or disable (set to 0) the feature of optimizing vmemmap pages diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h index 20d7edf62a6a..e0b2209ab71c 100644 --- a/include/linux/memory_hotplug.h +++ b/include/linux/memory_hotplug.h @@ -351,13 +351,4 @@ void arch_remove_linear_mapping(u64 start, u64 size); extern bool mhp_supports_memmap_on_memory(unsigned long size); #endif /* CONFIG_MEMORY_HOTPLUG */ -#ifdef CONFIG_MHP_MEMMAP_ON_MEMORY -bool mhp_memmap_on_memory(void); -#else -static inline bool mhp_memmap_on_memory(void) -{ - return false; -} -#endif - #endif /* __LINUX_MEMORY_HOTPLUG_H */ diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 2cf2a76535ab..607a4fcabbd4 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1434,6 +1434,7 @@ extern size_t mem_section_usage_size(void); MAPPER(IS_ONLINE) \ MAPPER(IS_EARLY) \ MAPPER(TAINT_ZONE_DEVICE, CONFIG_ZONE_DEVICE) \ + MAPPER(CANNOT_OPTIMIZE_VMEMMAP, CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP) \ MAPPER(MAP_LAST_BIT) #define __SECTION_SHIFT_FLAG_MAPPER_0(x) @@ -1471,6 +1472,22 @@ static inline struct page *__section_mem_map_addr(struct mem_section *section) return (struct page *)map; } +#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP +static inline void section_mark_cannot_optimize_vmemmap(struct mem_section *ms) +{ + ms->section_mem_map |= SECTION_CANNOT_OPTIMIZE_VMEMMAP; +} + +static inline int section_cannot_optimize_vmemmap(struct mem_section *ms) +{ + return (ms && (ms->section_mem_map & SECTION_CANNOT_OPTIMIZE_VMEMMAP)); +} +#else +static inline void section_mark_cannot_optimize_vmemmap(struct mem_section *ms) +{ +} +#endif + static inline int present_section(struct mem_section *section) { return (section && (section->section_mem_map & SECTION_MARKED_PRESENT)); diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c index fcd9f7872064..f12170520337 100644 --- a/mm/hugetlb_vmemmap.c +++ b/mm/hugetlb_vmemmap.c @@ -97,18 +97,32 @@ int hugetlb_vmemmap_alloc(struct hstate *h, struct page *head) return ret; } +static unsigned int optimizable_vmemmap_pages(struct hstate *h, + struct page *head) +{ + unsigned long pfn = page_to_pfn(head); + unsigned long end = pfn + pages_per_huge_page(h); + + if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF) + return 0; + + for (; pfn < end; pfn += PAGES_PER_SECTION) { + if (section_cannot_optimize_vmemmap(__pfn_to_section(pfn))) + return 0; + } + + return hugetlb_optimize_vmemmap_pages(h); +} + void hugetlb_vmemmap_free(struct hstate *h, struct page *head) { unsigned long vmemmap_addr = (unsigned long)head; unsigned long vmemmap_end, vmemmap_reuse, vmemmap_pages; - vmemmap_pages = hugetlb_optimize_vmemmap_pages(h); + vmemmap_pages = optimizable_vmemmap_pages(h, head); if (!vmemmap_pages) return; - if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF) - return; - static_branch_inc(&hugetlb_optimize_vmemmap_key); vmemmap_addr += RESERVE_VMEMMAP_SIZE; @@ -199,10 +213,10 @@ static struct ctl_table hugetlb_vmemmap_sysctls[] = { static __init int hugetlb_vmemmap_sysctls_init(void) { /* - * If "memory_hotplug.memmap_on_memory" is enabled or "struct page" - * crosses page boundaries, the vmemmap pages cannot be optimized. + * If "struct page" crosses page boundaries, the vmemmap pages cannot + * be optimized. */ - if (!mhp_memmap_on_memory() && is_power_of_2(sizeof(struct page))) + if (is_power_of_2(sizeof(struct page))) register_sysctl_init("vm", hugetlb_vmemmap_sysctls); return 0; diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 3b360eda933f..7309694c4dee 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -43,30 +43,22 @@ #include "shuffle.h" #ifdef CONFIG_MHP_MEMMAP_ON_MEMORY -static int memmap_on_memory_set(const char *val, const struct kernel_param *kp) -{ - if (hugetlb_optimize_vmemmap_enabled()) - return 0; - return param_set_bool(val, kp); -} - -static const struct kernel_param_ops memmap_on_memory_ops = { - .flags = KERNEL_PARAM_OPS_FL_NOARG, - .set = memmap_on_memory_set, - .get = param_get_bool, -}; - /* * memory_hotplug.memmap_on_memory parameter */ static bool memmap_on_memory __ro_after_init; -module_param_cb(memmap_on_memory, &memmap_on_memory_ops, &memmap_on_memory, 0444); +module_param(memmap_on_memory, bool, 0444); MODULE_PARM_DESC(memmap_on_memory, "Enable memmap on memory for memory hotplug"); -bool mhp_memmap_on_memory(void) +static inline bool mhp_memmap_on_memory(void) { return memmap_on_memory; } +#else +static inline bool mhp_memmap_on_memory(void) +{ + return false; +} #endif enum { diff --git a/mm/sparse.c b/mm/sparse.c index cb3bfae64036..1f353bf9ea6b 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -913,6 +913,14 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn, ms = __nr_to_section(section_nr); set_section_nid(section_nr, nid); __section_mark_present(ms, section_nr); + /* + * Mark whole section as non-optimizable once there is a subsection + * whose vmemmap pages are allocated from alternative allocator. The + * early section is always optimizable since the early section's + * vmemmap pages do not consider partially being populated. + */ + if (!early_section(ms) && altmap) + section_mark_cannot_optimize_vmemmap(ms); /* Align memmap to section boundary in the subsection case */ if (section_nr_to_pfn(section_nr) != start_pfn)