From: Zi Yan Date: Tue, 17 Jun 2025 02:11:09 +0000 (-0400) Subject: mm/page_alloc: pageblock flags functions clean up X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=42f46ed99ac6c07adf7f3bcbe9040b0c52d62d0f;p=thirdparty%2Fkernel%2Flinux.git mm/page_alloc: pageblock flags functions clean up Patch series "Make MIGRATE_ISOLATE a standalone bit", v10. This patchset moves MIGRATE_ISOLATE to a standalone bit to avoid being overwritten during pageblock isolation process. Currently, MIGRATE_ISOLATE is part of enum migratetype (in include/linux/mmzone.h), thus, setting a pageblock to MIGRATE_ISOLATE overwrites its original migratetype. This causes pageblock migratetype loss during alloc_contig_range() and memory offline, especially when the process fails due to a failed pageblock isolation and the code tries to undo the finished pageblock isolations. In terms of performance for changing pageblock types, no performance change is observed: 1. I used perf to collect stats of offlining and onlining all memory of a 40GB VM 10 times and see that get_pfnblock_flags_mask() and set_pfnblock_flags_mask() take about 0.12% and 0.02% of the whole process respectively with and without this patchset across 3 runs. 2. I used perf to collect stats of dd from /dev/random to a 40GB tmpfs file and find get_pfnblock_flags_mask() takes about 0.05% of the process with and without this patchset across 3 runs. This patch (of 6): No functional change is intended. 1. Add __NR_PAGEBLOCK_BITS for the number of pageblock flag bits and use roundup_pow_of_two(__NR_PAGEBLOCK_BITS) as NR_PAGEBLOCK_BITS to take right amount of bits for pageblock flags. 2. Rename PB_migrate_skip to PB_compact_skip. 3. Add {get,set,clear}_pfnblock_bit() to operate one a standalone bit, like PB_compact_skip. 3. Make {get,set}_pfnblock_flags_mask() internal functions and use {get,set}_pfnblock_migratetype() for pageblock migratetype operations. 4. Move pageblock flags common code to get_pfnblock_bitmap_bitidx(). 3. Use MIGRATETYPE_MASK to get the migratetype of a pageblock from its flags. 4. Use PB_migrate_end in the definition of MIGRATETYPE_MASK instead of PB_migrate_bits. 5. Add a comment on is_migrate_cma_folio() to prevent one from changing it to use get_pageblock_migratetype() and causing issues. Link: https://lkml.kernel.org/r/20250617021115.2331563-1-ziy@nvidia.com Link: https://lkml.kernel.org/r/20250617021115.2331563-2-ziy@nvidia.com Signed-off-by: Zi Yan Reviewed-by: Vlastimil Babka Acked-by: David Hildenbrand Cc: Baolin Wang Cc: Brendan Jackman Cc: Johannes Weiner Cc: Kirill A. Shuemov Cc: Mel Gorman Cc: Michal Hocko Cc: Oscar Salvador Cc: Richard Chang Cc: Suren Baghdasaryan Signed-off-by: Andrew Morton --- diff --git a/Documentation/mm/physical_memory.rst b/Documentation/mm/physical_memory.rst index d3ac106e6b143..9af11b5bd1459 100644 --- a/Documentation/mm/physical_memory.rst +++ b/Documentation/mm/physical_memory.rst @@ -584,7 +584,7 @@ Compaction control ``compact_blockskip_flush`` Set to true when compaction migration scanner and free scanner meet, which - means the ``PB_migrate_skip`` bits should be cleared. + means the ``PB_compact_skip`` bits should be cleared. ``contiguous`` Set to true when the zone is contiguous (in other words, no hole). diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 5bec8b1d0e665..76d66c07b673a 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -92,8 +92,12 @@ extern const char * const migratetype_names[MIGRATE_TYPES]; #ifdef CONFIG_CMA # define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA) # define is_migrate_cma_page(_page) (get_pageblock_migratetype(_page) == MIGRATE_CMA) -# define is_migrate_cma_folio(folio, pfn) (MIGRATE_CMA == \ - get_pfnblock_flags_mask(&folio->page, pfn, MIGRATETYPE_MASK)) +/* + * __dump_folio() in mm/debug.c passes a folio pointer to on-stack struct folio, + * so folio_pfn() cannot be used and pfn is needed. + */ +# define is_migrate_cma_folio(folio, pfn) \ + (get_pfnblock_migratetype(&folio->page, pfn) == MIGRATE_CMA) #else # define is_migrate_cma(migratetype) false # define is_migrate_cma_page(_page) false @@ -122,14 +126,12 @@ static inline bool migratetype_is_mergeable(int mt) extern int page_group_by_mobility_disabled; -#define MIGRATETYPE_MASK ((1UL << PB_migratetype_bits) - 1) +#define get_pageblock_migratetype(page) \ + get_pfnblock_migratetype(page, page_to_pfn(page)) -#define get_pageblock_migratetype(page) \ - get_pfnblock_flags_mask(page, page_to_pfn(page), MIGRATETYPE_MASK) +#define folio_migratetype(folio) \ + get_pageblock_migratetype(&folio->page) -#define folio_migratetype(folio) \ - get_pfnblock_flags_mask(&folio->page, folio_pfn(folio), \ - MIGRATETYPE_MASK) struct free_area { struct list_head free_list[MIGRATE_TYPES]; unsigned long nr_free; diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h index 898bb788243b2..277d8d92980c2 100644 --- a/include/linux/page-isolation.h +++ b/include/linux/page-isolation.h @@ -25,7 +25,7 @@ static inline bool is_migrate_isolate(int migratetype) #define MEMORY_OFFLINE 0x1 #define REPORT_FAILURE 0x2 -void set_pageblock_migratetype(struct page *page, int migratetype); +void set_pageblock_migratetype(struct page *page, enum migratetype migratetype); bool move_freepages_block_isolate(struct zone *zone, struct page *page, int migratetype); diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h index 6297c6343c553..c240c7a1fb038 100644 --- a/include/linux/pageblock-flags.h +++ b/include/linux/pageblock-flags.h @@ -19,15 +19,19 @@ enum pageblock_bits { PB_migrate, PB_migrate_end = PB_migrate + PB_migratetype_bits - 1, /* 3 bits required for migrate types */ - PB_migrate_skip,/* If set the block is skipped by compaction */ + PB_compact_skip,/* If set the block is skipped by compaction */ /* * Assume the bits will always align on a word. If this assumption * changes then get/set pageblock needs updating. */ - NR_PAGEBLOCK_BITS + __NR_PAGEBLOCK_BITS }; +#define NR_PAGEBLOCK_BITS (roundup_pow_of_two(__NR_PAGEBLOCK_BITS)) + +#define MIGRATETYPE_MASK ((1UL << (PB_migrate_end + 1)) - 1) + #if defined(CONFIG_HUGETLB_PAGE) #ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE @@ -65,27 +69,23 @@ extern unsigned int pageblock_order; /* Forward declaration */ struct page; -unsigned long get_pfnblock_flags_mask(const struct page *page, - unsigned long pfn, - unsigned long mask); - -void set_pfnblock_flags_mask(struct page *page, - unsigned long flags, - unsigned long pfn, - unsigned long mask); +enum migratetype get_pfnblock_migratetype(const struct page *page, + unsigned long pfn); +bool get_pfnblock_bit(const struct page *page, unsigned long pfn, + enum pageblock_bits pb_bit); +void set_pfnblock_bit(const struct page *page, unsigned long pfn, + enum pageblock_bits pb_bit); +void clear_pfnblock_bit(const struct page *page, unsigned long pfn, + enum pageblock_bits pb_bit); /* Declarations for getting and setting flags. See mm/page_alloc.c */ #ifdef CONFIG_COMPACTION #define get_pageblock_skip(page) \ - get_pfnblock_flags_mask(page, page_to_pfn(page), \ - (1 << (PB_migrate_skip))) + get_pfnblock_bit(page, page_to_pfn(page), PB_compact_skip) #define clear_pageblock_skip(page) \ - set_pfnblock_flags_mask(page, 0, page_to_pfn(page), \ - (1 << PB_migrate_skip)) + clear_pfnblock_bit(page, page_to_pfn(page), PB_compact_skip) #define set_pageblock_skip(page) \ - set_pfnblock_flags_mask(page, (1 << PB_migrate_skip), \ - page_to_pfn(page), \ - (1 << PB_migrate_skip)) + set_pfnblock_bit(page, page_to_pfn(page), PB_compact_skip) #else static inline bool get_pageblock_skip(struct page *page) { diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index a371d59cc7189..403221982c2ea 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -774,7 +774,7 @@ void move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn, /* * TODO now we have a visible range of pages which are not associated - * with their zone properly. Not nice but set_pfnblock_flags_mask + * with their zone properly. Not nice but set_pfnblock_migratetype() * expects the zone spans the pfn range. All the pages in the range * are reserved so nobody should be touching them so we should be safe */ diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 31041e2aa33a7..43a4c15327217 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -353,81 +353,174 @@ static inline int pfn_to_bitidx(const struct page *page, unsigned long pfn) return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS; } +static __always_inline bool is_standalone_pb_bit(enum pageblock_bits pb_bit) +{ + return pb_bit > PB_migrate_end && pb_bit < __NR_PAGEBLOCK_BITS; +} + +static __always_inline void +get_pfnblock_bitmap_bitidx(const struct page *page, unsigned long pfn, + unsigned long **bitmap_word, unsigned long *bitidx) +{ + unsigned long *bitmap; + unsigned long word_bitidx; + + BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4); + BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits)); + VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page); + + bitmap = get_pageblock_bitmap(page, pfn); + *bitidx = pfn_to_bitidx(page, pfn); + word_bitidx = *bitidx / BITS_PER_LONG; + *bitidx &= (BITS_PER_LONG - 1); + *bitmap_word = &bitmap[word_bitidx]; +} + + /** - * get_pfnblock_flags_mask - Return the requested group of flags for the pageblock_nr_pages block of pages + * __get_pfnblock_flags_mask - Return the requested group of flags for + * a pageblock_nr_pages block of pages * @page: The page within the block of interest * @pfn: The target page frame number * @mask: mask of bits that the caller is interested in * * Return: pageblock_bits flags */ -unsigned long get_pfnblock_flags_mask(const struct page *page, - unsigned long pfn, unsigned long mask) +static unsigned long __get_pfnblock_flags_mask(const struct page *page, + unsigned long pfn, + unsigned long mask) { - unsigned long *bitmap; - unsigned long bitidx, word_bitidx; + unsigned long *bitmap_word; + unsigned long bitidx; unsigned long word; - bitmap = get_pageblock_bitmap(page, pfn); - bitidx = pfn_to_bitidx(page, pfn); - word_bitidx = bitidx / BITS_PER_LONG; - bitidx &= (BITS_PER_LONG-1); + get_pfnblock_bitmap_bitidx(page, pfn, &bitmap_word, &bitidx); /* - * This races, without locks, with set_pfnblock_flags_mask(). Ensure + * This races, without locks, with set_pfnblock_migratetype(). Ensure * a consistent read of the memory array, so that results, even though * racy, are not corrupted. */ - word = READ_ONCE(bitmap[word_bitidx]); + word = READ_ONCE(*bitmap_word); return (word >> bitidx) & mask; } -static __always_inline int get_pfnblock_migratetype(const struct page *page, - unsigned long pfn) +/** + * get_pfnblock_bit - Check if a standalone bit of a pageblock is set + * @page: The page within the block of interest + * @pfn: The target page frame number + * @pb_bit: pageblock bit to check + * + * Return: true if the bit is set, otherwise false + */ +bool get_pfnblock_bit(const struct page *page, unsigned long pfn, + enum pageblock_bits pb_bit) { - return get_pfnblock_flags_mask(page, pfn, MIGRATETYPE_MASK); + unsigned long *bitmap_word; + unsigned long bitidx; + + if (WARN_ON_ONCE(!is_standalone_pb_bit(pb_bit))) + return false; + + get_pfnblock_bitmap_bitidx(page, pfn, &bitmap_word, &bitidx); + + return test_bit(bitidx + pb_bit, bitmap_word); } /** - * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages + * get_pfnblock_migratetype - Return the migratetype of a pageblock + * @page: The page within the block of interest + * @pfn: The target page frame number + * + * Return: The migratetype of the pageblock + * + * Use get_pfnblock_migratetype() if caller already has both @page and @pfn + * to save a call to page_to_pfn(). + */ +__always_inline enum migratetype +get_pfnblock_migratetype(const struct page *page, unsigned long pfn) +{ + return __get_pfnblock_flags_mask(page, pfn, MIGRATETYPE_MASK); +} + +/** + * __set_pfnblock_flags_mask - Set the requested group of flags for + * a pageblock_nr_pages block of pages * @page: The page within the block of interest - * @flags: The flags to set * @pfn: The target page frame number + * @flags: The flags to set * @mask: mask of bits that the caller is interested in */ -void set_pfnblock_flags_mask(struct page *page, unsigned long flags, - unsigned long pfn, - unsigned long mask) +static void __set_pfnblock_flags_mask(struct page *page, unsigned long pfn, + unsigned long flags, unsigned long mask) { - unsigned long *bitmap; - unsigned long bitidx, word_bitidx; + unsigned long *bitmap_word; + unsigned long bitidx; unsigned long word; - BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4); - BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits)); - - bitmap = get_pageblock_bitmap(page, pfn); - bitidx = pfn_to_bitidx(page, pfn); - word_bitidx = bitidx / BITS_PER_LONG; - bitidx &= (BITS_PER_LONG-1); - - VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page); + get_pfnblock_bitmap_bitidx(page, pfn, &bitmap_word, &bitidx); mask <<= bitidx; flags <<= bitidx; - word = READ_ONCE(bitmap[word_bitidx]); + word = READ_ONCE(*bitmap_word); do { - } while (!try_cmpxchg(&bitmap[word_bitidx], &word, (word & ~mask) | flags)); + } while (!try_cmpxchg(bitmap_word, &word, (word & ~mask) | flags)); +} + +/** + * set_pfnblock_bit - Set a standalone bit of a pageblock + * @page: The page within the block of interest + * @pfn: The target page frame number + * @pb_bit: pageblock bit to set + */ +void set_pfnblock_bit(const struct page *page, unsigned long pfn, + enum pageblock_bits pb_bit) +{ + unsigned long *bitmap_word; + unsigned long bitidx; + + if (WARN_ON_ONCE(!is_standalone_pb_bit(pb_bit))) + return; + + get_pfnblock_bitmap_bitidx(page, pfn, &bitmap_word, &bitidx); + + set_bit(bitidx + pb_bit, bitmap_word); } -void set_pageblock_migratetype(struct page *page, int migratetype) +/** + * clear_pfnblock_bit - Clear a standalone bit of a pageblock + * @page: The page within the block of interest + * @pfn: The target page frame number + * @pb_bit: pageblock bit to clear + */ +void clear_pfnblock_bit(const struct page *page, unsigned long pfn, + enum pageblock_bits pb_bit) +{ + unsigned long *bitmap_word; + unsigned long bitidx; + + if (WARN_ON_ONCE(!is_standalone_pb_bit(pb_bit))) + return; + + get_pfnblock_bitmap_bitidx(page, pfn, &bitmap_word, &bitidx); + + clear_bit(bitidx + pb_bit, bitmap_word); +} + +/** + * set_pageblock_migratetype - Set the migratetype of a pageblock + * @page: The page within the block of interest + * @migratetype: migratetype to set + */ +__always_inline void set_pageblock_migratetype(struct page *page, + enum migratetype migratetype) { if (unlikely(page_group_by_mobility_disabled && migratetype < MIGRATE_PCPTYPES)) migratetype = MIGRATE_UNMOVABLE; - set_pfnblock_flags_mask(page, (unsigned long)migratetype, - page_to_pfn(page), MIGRATETYPE_MASK); + __set_pfnblock_flags_mask(page, page_to_pfn(page), + (unsigned long)migratetype, MIGRATETYPE_MASK); } #ifdef CONFIG_DEBUG_VM @@ -667,7 +760,7 @@ static inline void __add_to_free_list(struct page *page, struct zone *zone, int nr_pages = 1 << order; VM_WARN_ONCE(get_pageblock_migratetype(page) != migratetype, - "page type is %lu, passed migratetype is %d (nr=%d)\n", + "page type is %d, passed migratetype is %d (nr=%d)\n", get_pageblock_migratetype(page), migratetype, nr_pages); if (tail) @@ -693,7 +786,7 @@ static inline void move_to_free_list(struct page *page, struct zone *zone, /* Free page moving can fail, so it happens before the type update */ VM_WARN_ONCE(get_pageblock_migratetype(page) != old_mt, - "page type is %lu, passed migratetype is %d (nr=%d)\n", + "page type is %d, passed migratetype is %d (nr=%d)\n", get_pageblock_migratetype(page), old_mt, nr_pages); list_move_tail(&page->buddy_list, &area->free_list[new_mt]); @@ -715,7 +808,7 @@ static inline void __del_page_from_free_list(struct page *page, struct zone *zon int nr_pages = 1 << order; VM_WARN_ONCE(get_pageblock_migratetype(page) != migratetype, - "page type is %lu, passed migratetype is %d (nr=%d)\n", + "page type is %d, passed migratetype is %d (nr=%d)\n", get_pageblock_migratetype(page), migratetype, nr_pages); /* clear reported state and update reported page count */ @@ -3123,7 +3216,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone, /* * Do not instrument rmqueue() with KMSAN. This function may call - * __msan_poison_alloca() through a call to set_pfnblock_flags_mask(). + * __msan_poison_alloca() through a call to set_pfnblock_migratetype(). * If __msan_poison_alloca() attempts to allocate pages for the stack depot, it * may call rmqueue() again, which will result in a deadlock. */