[RFT PATCH v1 4/5] mm: provide more accurate estimation of pages occupied by memmap
From: Jiang Liu <hidden>
Date: 2012-11-18 16:10:07
Also in:
lkml
Subsystem:
memory management, memory management - page allocator, the rest · Maintainers:
Andrew Morton, Vlastimil Babka, Linus Torvalds
If SPARSEMEM is enabled, it won't build page structures for non-existing pages (holes) within a zone, so provide a more accurate estimation of pages occupied by memmap if there are big holes within the zone. And pages for highmem zones' memmap will be allocated from lowmem, so charge nr_kernel_pages for that. Signed-off-by: Jiang Liu <redacted> --- mm/page_alloc.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5b327d7..eb25679 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c@@ -4435,6 +4435,22 @@ void __init set_pageblock_order(void) #endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */ +static unsigned long calc_memmap_size(unsigned long spanned_pages, + unsigned long present_pages) +{ + unsigned long pages = spanned_pages; + + /* + * Provide a more accurate estimation if there are big holes within + * the zone and SPARSEMEM is in use. + */ + 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
@@ -4469,8 +4485,7 @@ 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)
@@ -4491,6 +4506,9 @@ 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;
--
1.7.9.5
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