From 42f46ed99ac6c07adf7f3bcbe9040b0c52d62d0f Mon Sep 17 00:00:00 2001 From: Zi Yan Date: Mon, 16 Jun 2025 22:11:09 -0400 Subject: 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 --- include/linux/pageblock-flags.h | 34 +++++++++++++++++----------------- 1 file changed, 17 insertions(+), 17 deletions(-) (limited to 'include/linux/pageblock-flags.h') diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h index 6297c6343c55..c240c7a1fb03 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) { -- cgit v1.2.3