About bootmem allocation/freeing flow
hi all: I have several questions about free_all_bootmem_core: 1. In __free_pages_bootmem, we set set_page_count(p, 0) while looping nr_pages, why we need to set_page_refcounted(page) before calling __free_pages? 2. how about the pages that allocated by calling alloc_bootmem_xxxx? in free_all_bootmem, we just free the pages that used to record bootmem stage present pages like below. if so, isn't possible the pages got by calling alloc_bootmem_xxxx will be over-written by later page allocation ? page = virt_to_page(bdata->node_bootmem_map); pages = bdata->node_low_pfn - bdata->node_min_pfn; pages = bootmem_bootmap_pages(pages); count += pages; while (pages--) __free_pages_bootmem(page++, 0); appreciate your kind help in advance,
2015-04-18 15:28 GMT+08:00 yoma sophian <sophian.yoma@gmail.com>:
hi all: I have several questions about free_all_bootmem_core:
1. In __free_pages_bootmem, we set set_page_count(p, 0) while looping nr_pages, why we need to set_page_refcounted(page) before calling __free_pages? below is excerpted from mm/page_alloc.c and mm/internal.h the reason why we use set_page_refcounted(page) is because set_page_refcounted(page) will calling VM_BUG_ON to checking page property?
static inline void set_page_refcounted(struct page *page) { VM_BUG_ON(PageTail(page)); VM_BUG_ON(atomic_read(&page->_ count)); set_page_count(page, 1); } void __meminit __free_pages_bootmem(struct page *page, unsigned int order) { unsigned int nr_pages = 1 << order; unsigned int loop; prefetchw(page); for (loop = 0; loop < nr_pages; loop++) { struct page *p = &page[loop]; if (loop + 1 < nr_pages) prefetchw(p + 1); __ClearPageReserved(p); set_page_count(p, 0); } page_zone(page)->managed_pages += 1 << order; set_page_refcounted(page); __free_pages(page, order); } thanks for your help,
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yoma sophian