diff options
| -rw-r--r-- | mm/page_alloc.c | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 0b6a6d04300a..d187988e2b56 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4489,6 +4489,26 @@ void __init set_pageblock_order(void) #endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */ +static unsigned long __paginginit calc_memmap_size(unsigned long spanned_pages, + unsigned long present_pages) +{ + unsigned long pages = spanned_pages; + + /* + * Provide a more accurate estimation if there are holes within + * the zone and SPARSEMEM is in use. If there are holes within the + * zone, each populated memory region may cost us one or two extra + * memmap pages due to alignment because memmap pages for each + * populated regions may not naturally algined on page boundary. + * So the (present_pages >> 4) heuristic is a tradeoff for that. + */ + if (spanned_pages > present_pages + (present_pages >> 4) && + IS_ENABLED(CONFIG_SPARSEMEM)) + pages = present_pages; + + return PAGE_ALIGN(pages * sizeof(struct page)) >> PAGE_SHIFT; +} + /* * Set up the zone data structures: * - mark all pages reserved @@ -4523,8 +4543,7 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat, * is used by this zone for memmap. This affects the watermark * and per-cpu initialisations */ - memmap_pages = - PAGE_ALIGN(size * sizeof(struct page)) >> PAGE_SHIFT; + memmap_pages = calc_memmap_size(size, realsize); if (freesize >= memmap_pages) { freesize -= memmap_pages; if (memmap_pages) @@ -4545,6 +4564,9 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat, if (!is_highmem_idx(j)) nr_kernel_pages += freesize; + /* Charge for highmem memmap if there are enough kernel pages */ + else if (nr_kernel_pages > memmap_pages * 2) + nr_kernel_pages -= memmap_pages; nr_all_pages += freesize; zone->spanned_pages = size; |