memmap_init_range() would init page count of all pages, but the free pages count would be reset in __free_pages_core(). There are opposite operations. It's unnecessary and time-consuming when it's MEMINIT_EARLY context. Init page count in reserve_bootmem_region when in MEMINIT_EARLY context, and check the page count before reset it. At the same time, the INIT_LIST_HEAD in reserve_bootmem_region isn't need, as it already done in __init_single_page. The following data was tested on an x86 machine with 190GB of RAM. before: free_low_memory_core_early() 341ms after: free_low_memory_core_early() 285ms Signed-off-by: Yajun Deng <yajun.deng@xxxxxxxxx> --- v4: same with v2. v3: same with v2. v2: check page count instead of check context before reset it. v1: https://lore.kernel.org/all/20230922070923.355656-1-yajun.deng@xxxxxxxxx/ --- mm/mm_init.c | 18 +++++++++++++----- mm/page_alloc.c | 20 ++++++++++++-------- 2 files changed, 25 insertions(+), 13 deletions(-) diff --git a/mm/mm_init.c b/mm/mm_init.c index 9716c8a7ade9..3ab8861e1ef3 100644 --- a/mm/mm_init.c +++ b/mm/mm_init.c @@ -718,7 +718,7 @@ static void __meminit init_reserved_page(unsigned long pfn, int nid) if (zone_spans_pfn(zone, pfn)) break; } - __init_single_page(pfn_to_page(pfn), pfn, zid, nid, INIT_PAGE_COUNT); + __init_single_page(pfn_to_page(pfn), pfn, zid, nid, 0); } #else static inline void pgdat_set_deferred_range(pg_data_t *pgdat) {} @@ -756,8 +756,8 @@ void __meminit reserve_bootmem_region(phys_addr_t start, init_reserved_page(start_pfn, nid); - /* Avoid false-positive PageTail() */ - INIT_LIST_HEAD(&page->lru); + /* Init page count for reserved region */ + init_page_count(page); /* * no need for atomic set_bit because the struct @@ -888,9 +888,17 @@ void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone } page = pfn_to_page(pfn); - __init_single_page(page, pfn, zone, nid, INIT_PAGE_COUNT); - if (context == MEMINIT_HOTPLUG) + + /* If the context is MEMINIT_EARLY, we will init page count and + * mark page reserved in reserve_bootmem_region, the free region + * wouldn't have page count and we will check the pages count + * in __free_pages_core. + */ + __init_single_page(page, pfn, zone, nid, 0); + if (context == MEMINIT_HOTPLUG) { + init_page_count(page); __SetPageReserved(page); + } /* * Usually, we want to mark the pageblock MIGRATE_MOVABLE, diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 06be8821d833..b868caabe8dc 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1285,18 +1285,22 @@ void __free_pages_core(struct page *page, unsigned int order) unsigned int loop; /* - * When initializing the memmap, __init_single_page() sets the refcount - * of all pages to 1 ("allocated"/"not free"). We have to set the - * refcount of all involved pages to 0. + * When initializing the memmap, memmap_init_range sets the refcount + * of all pages to 1 ("reserved" and "free") in hotplug context. We + * have to set the refcount of all involved pages to 0. Otherwise, + * we don't do it, as reserve_bootmem_region only set the refcount on + * reserve region ("reserved") in early context. */ - prefetchw(p); - for (loop = 0; loop < (nr_pages - 1); loop++, p++) { - prefetchw(p + 1); + if (page_count(page)) { + prefetchw(p); + for (loop = 0; loop < (nr_pages - 1); loop++, p++) { + prefetchw(p + 1); + __ClearPageReserved(p); + set_page_count(p, 0); + } __ClearPageReserved(p); set_page_count(p, 0); } - __ClearPageReserved(p); - set_page_count(p, 0); atomic_long_add(nr_pages, &page_zone(page)->managed_pages); -- 2.25.1
